Engine Concern (perceived mis)

Any of you guys have a suggestion on the issue I'm having?

Superior IO-360 with high compression pistons (185hp), Hartzell Blended Airfoil, Silver Hawk fuel servo(Bendix) with ram air (no filter at the moment), Slick mag on the left, Lightspeed ignition on the right. The engine has about 130 hrs on it now. The engine starts easily and generally runs fantastic on the ground and feels/sounds strong during takeoff and climb. That being said, when I power back to say 21" and 2450 RPM, the engine generally sounds good, but I detect an intermittent "miss" or hesitation. Its just enough to make me not fully trust the engine 100% and it wears on my mind. The Dynon D180 shows the engine as being perfectly healthy. All the CHT's and EGTs look great and within a few degrees of one another. Oil temp stays in the 180 degree range. When I do my engine runup, I get a big decrease in RPM if I turn off the Electronic (probably 200 or 300 rpm), so the mag seems weak. When I turn off the mag of course, there's very little drop. In flight, if I turn off the EI, the engine of course runs poorly, so it's hard to tell, but I think I still feel the intermittent miss. If I turn off the Mag, I still think I feel the miss. I've checked timing on both the Mag and EI. I've verified that the coax wires coming from the electronic ignition aren't in close proximity to the crank sensor wires. I've monitored fuel pressures. The boost pump doesn't make any difference in the "miss". To me, it seem to be related to ignition. I've pulled the prop and verified the correct location of the sensor magnets, the spacing between the sensors and flywheel magnets and I've confirmed correct orientation / timing of the flywheel to the crank sensor.

With the above in mind, whats the likelihood of having an intermittent stuck valve that's causing my problem? Do valves intermittently stick? Does a sticky valve ALWAYS show up on electronic engine monitors? I'm not seeing any power loss or anything reflected in EGT or CHT's on the Dynon. Its rock solid as far as temps. The only thing I've noticed that seems to make the "mis" either go away or become less detectible is to run higher RPM's and MP's. During takeoff, at full power and high RPM, I've never noticed the mis and it runs strong. It only seems to be a constant issue at more reasonable cruise power settings where I always want to run to conserve fuel. Mixture setting doesn't seem to affect the mis whatsoever.

Any help would be appreciated as I'm running out of ideas. I'm considering going dual electronic ignition or installing a bendix mag which I've been told produces a stronger spark than today's slick mags, but I'm just not sure the mag is my problem (even though I feel it's weak considering the amount of mag drop I'm getting). My friend has the same exact engine/mag/electronic ignition setup in his 7A (but with standard compression) and his engine runs GREAT!

Any Ideas?

Chad

Is the flywheel magnet-to-sensor gap maybe becoming too large when you pull on the prop? There is some play there and the gap will definitely change when the prop is pulling the airplane.

Chad,

The best way to troubleshoot this "phantom miss" is to make a flight on a moonless cloudy night over a large body of water. Studies have shown that the average pilot's sense of hearing is vastly improved under these conditions.

Sorry - wish I could help with some tidbits of knowledge that were actually useful!

But really - I have the same setup (Lightspeed and Mag). I have the same RPM drop on run-up of about 250 RPM. I don't consider it to be a problem, because the LS Ign is so strong, the Magneto just doesn't have the output to match it.

You asked about the possibility of a stuck valve. You would see a stuck valve on your EGT. Pretty tough to get an "intermittent" stuck valve, so that's probably not the problem.

You might want to aggressively drain both sumps for water, as well as clean the fuel filter. Also, make sure your injectors are clean.

Finally, download your EMS data and scrutinize it. If everything is, as you said, "perfectly healthy", then you're probably OK.

Good luck!

First thing I would do is eliminate the easiest thing and that would be to change the spark plugs.

Miss

I don't know the first thing about electronic ignition but I've had these exact symtoms in the past. I had an intermittent miss that I couldn't figure out for about 25 or more hours. I finally saw the egt blip and changed the plugs in the offending cylinder. Problem solved. I also think there is a strong chance you have a plug problem.

The plug that caused me all the problems was a nearly new Champion.

rocketbob said:

First thing I would do is eliminate the easiest thing and that would be to change the spark plugs.

Click to expand...

Bob has a great point...I had a very, very slight miss a year and a half ago while flying to Reno. I've got dual electronic ignition (PMags) and it normally runs smooth as silk, so when it missed it caught my attention. Upon returning home, I pulled the plugs and found that they all had tiny lead balls stuck to them. Changed them out (auto plugs at $2.50 each) and it went back to running perfectly. Since then I've mostly been running auto gas. Problem has not returned.

Another simple check

Others have mentioned the plugs and that is a good and simple idea.

I had a similar problem. Cleaned the plugs and it would still happen during a certain RPM range. I would think if it was ignition, it would be pretty much across the board.

Discussed it with one of our local A&P's. He suggested that I check the Fuel Injection system. He showed my how to pull the lines from the cylinders and place a cup under each one. The fuel pump was turned on, throttle full. We ran this for about 20 seconds or so to get about half a cup.

Well the Number 1 cylinder only had about half as much fuel in the cup indicating some sort of blockage. I pulled that line from the spider and flushed it. I found a small speck of black rubber material in the line. I also checked the spider and found it clean.

Everything was put back together and the engine performed flawlessly. The mechanic explained that the piece of rubber could be floating and cavitating in the line causing intermittent fuel flow. That lead to the inconsistency.

Good luck.

Spark

rocketbob said:

First thing I would do is eliminate the easiest thing and that would be to change the spark plugs.

Click to expand...

I agree with Bob, I would start with spark plugs, put them in a tester at 80 PSI and check the spark.

Pat

Start with the plugs as suggested
Valves: note egt's at the start in the morning and see if there is any difference, this is commonly called "morning sickness", but it they are just sticking a bit the engine still might idle ok but you may see a difference in the EGT. I have noticed a sticking valve in the air after a power reduction, just a subtle blip, and then gone. Nothing showed on the data but the pre take off egt data told the tale.
Mag: This last year I had a miss that I felt was ignition, I changed the plugs, spent a lot of time with the electronic ignition and finally sent the mag in for a check and an overhaul (500+hours). It turned out I had a cracked distributor cap and with that solved all the problems went away. I was a full month chasing that miss.

OK Gentlemen. Sounds like plugs first, then move forward with mag inspection. I do appreciate all your input. I'll post what I find. (sure hope I find something....)

Thanks!!!
Chad

Engine Concern

molson309 said:

Is the flywheel magnet-to-sensor gap maybe becoming too large when you pull on the prop? There is some play there and the gap will definitely change when the prop is pulling the airplane.

Click to expand...

Mark,

When I pulled the prop a while back, I went to extensive measures to verify the gap wasn't too large or too small whether pushing or pulling on the prop. The gap "should" be correct now. I came to the same conclusion as you a while back, so that's why I pulled the prop to investigate the gap. I found it a bit too close as there was a bit of evidence that the flywheel had actually rubbed the sensor assembly (ever so slightly) at some point in the past. I added a washer to move it a bit further away and rechecked the gaps with crank in and crank out.

Chad

Chad, you could bin all the plugs and put in new ones, but here are a few things to check.

1. Pull all the plugs and if you can test them for ceramic cracks.
2. Check the resistance for 1000-5000 ohms. Any more than 5kohm into the bin.
3. Gap the plugs to 16 to 18 though. Using the wire type gauge, do not use a flat feeler gauge like you would use on auto plugs. If they have not been regapped in the 130 hours, this is most likely the problem.
4. Auto plugs ...... Dunno, 25 thou I think is the gap of choice.
5. Best time to check your mags, plugs etc is at altitude, wot/LOP. Do it in the cruise or prior to TOD.

If you have Dynon data files, logged at 1 second intervals send them to me if you want.

DB

Today, I couldn't get ahold of new aviation plugs for the mags, but I did replace the electronic ignition automotive plugs. I'll replace the Aviation plugs on Monday when the store opens. I did fly the airplane and found that there was no difference. The engine still skips a beat ever few seconds (mis). I had a pilot/mechanic friend with me today just to confirm what I'm hearing. We alternated turning off the mag, then electronic ignition. We agreed that the "mis" continues, no matter which ignition source you use. This really concerns me since it sounds like my problem may be related to the engine itself, regardless of what the Dynon engine monitor indicates. I'll definitely try new plugs on the mag side to eliminate that possibility. In the meantime, if anyone has other suggestions,,, please speak up.

Thanks,

Chad

If the engine misses once in a while no matter what ignition source you use, I can't believe that it's being caused by a bad plug. In my mind that pretty much narrows it down to a mixture problem - whether it be due to induction or fuel delivery problems.

What happens to the miss if you start leaning the mixture? Does it become more pronounced, and if so, is the EGT on one cylinder showing signs of misfiring (dropping off faster than the rest)?

I think you really need to pay close attention to the engine monitor.

The secrets are here if you know what to look for. Do a data download and send it to me.

DakotaHawk said:

Chad,

The best way to troubleshoot this "phantom miss" is to make a flight on a moonless cloudy night over a large body of water. Studies have shown that the average pilot's sense of hearing is vastly improved under these conditions.

Sorry - wish I could help with some tidbits of knowledge that were actually useful!

But really - I have the same setup (Lightspeed and Mag). I have the same RPM drop on run-up of about 250 RPM. I don't consider it to be a problem, because the LS Ign is so strong, the Magneto just doesn't have the output to match it.

You asked about the possibility of a stuck valve. You would see a stuck valve on your EGT. Pretty tough to get an "intermittent" stuck valve, so that's probably not the problem.

You might want to aggressively drain both sumps for water, as well as clean the fuel filter. Also, make sure your injectors are clean.

Finally, download your EMS data and scrutinize it. If everything is, as you said, "perfectly healthy", then you're probably OK.

Good luck!

Click to expand...

Dakota,

Are you running a 9:1 compression Superior engine? if so, what ignition timing are your running? 20 degrees or 25 degrees? I was told by Superior that even though I have high compression, its ok to time it at 25 degrees unless I'm seeing high CHT's. My CHT's stay well under 400, so I've kept the timing at 25 degrees. Does anybody want to comment on their experience with high compression pistons and timing?

Chad

I have a Bendix mag on the left and Pmag on the right. Every now and then I would also have a slight miss while taxiing in. plugs, timing etc ok until one day the mag would not run at higher than idle speed on run up.

The condenser was loose! tightened...problem solved. I am not familiar with the slick, but the Bendix condenser is screwed on from the outside.

things that go bump

I flew an RV-4 for 18 years with a Sam Rose EI mounted in place of one mag. I also experienced the same roughness you speak of. I never resolved the issue but finally chalked it up to the EI being so smooth the mag seemed rough by comparison and once you've felt smooth it's hard to go back. After a few long flights you might find the roughness is not so noticeable.

Sounds like roughness is neither from the mag, nor the EI since the roughness is present when each ignition source is isolated.

Fuel system troubleshooting should be in order.

Keep us posted

Thanks for the input thus far. My engine miss seems to have gotten worse. I changed both EI coils as well as one ignition wire, but my problem remains. I'm confident the problem is ignition related. I'm pulling both systems tomorrow to have them tested. Can anyone recommend a good Slick mag OH facility? Im in the Dallas area.

Thanks,

Chad

Aircraft Specialties in Tulsa.

I have a slick mag with impulse coupler and an LSI plasma II box you could use for troubleshooting. You're also welcome to come by and we can chat about what's going on, I'm right down the road at 52F. I could even fly over to you with the stuff if you aren't comfortable coming over to me.

Check your intake clamps and hoses for leaks.

While you are having the mag rebuilt it would be a good time to check your injectors and the flow to them.

Thanks Pat, good idea. Walt, I might just take you up on your offer. Will give you a call if things don't get ironed out shortly. Gasman, a while back, I did an extensive inspection/testing of the intake tubes, but possibly I need to revisit. NickAir, your right. This is a good time to check the injectors again.

Thanks to everyone for your suggestions. Will let you know what I find,,,, or don't find...

Chad

Chad (or Walt, if you go over to help), double check the crimps on coax that run to the coils.

I while back I had an occasional miss on my Plasma II plugs. I changed the plugs which helped for a while then swapped out the coils which seemed to fix the problem. About 6 months later, I was doing some other maintenance which required removing the coil coax's, one of the terminals pulled off in the process ..... I think that was my problem all along - a bad crimp on one of the coil inputs.

Thanks Rick. Today, I removed the Lightspeed box, the coils, and the crank sensor to ship back to Klaus for testing. (and for the record, I'm not certain my problem is associated with the Lightspeed ignition). I haven't looked closely at the coax connections though,,, so I'll get that looked at tomorrow. Was your loose connection at the box or at the spade connection at the coil?

Check your fuel lines and filter for a sucking air leak and make sure your vent lines are clear.

Chad, my bad crimp was at the coil spade connector. The BNCthat connects to the LSE controller was done at the factory.

Even though I had done a pull test on the connector when I first did the crimp, it still got by me. I only discovered the poor crimp when I was getting ready to cut off the connector so I could re-route the coax. The spade connector came off in my hand as I was getting ready to cut it.

mag shop in lancaster

Speeddog7 said:

Thanks for the input thus far. My engine miss seems to have gotten worse. I changed both EI coils as well as one ignition wire, but my problem remains. I'm confident the problem is ignition related. I'm pulling both systems tomorrow to have them tested. Can anyone recommend a good Slick mag OH facility? Im in the Dallas area.

Thanks,

Chad

Click to expand...

Chad,

I've used Aaron over at Select Aircraft Services in LNC.

Anton

Anton,

I'd heard that there was a mag guy over there. Will give him a try. Thanks!

Milt, I checked for leaks a few weeks ago. I even plugged my gascolator / filter sump drain to verify the drain wasn't somehow sucking open. No change....

Rick, I'll test my spade connections as suggested. Thanks!!!

Chad

Perceived Engine Mis

Gentlemen,

Thought I'd give you an update. I had my mag bench checked. It received a clean bill of health. I also sent my Plasma III igntion box, coils, flywheel and crank sensor back to Klaus at LSE for him to inspect and test. Klaus said there was nothing wrong with my electronic ignition. While Klaus was checking my system, I decided to buy a second system from him and go Dual Electronic. I installed the dual system as well as upgraded to his new Mini-sensors (which I really liked because it got rid of the guesswork associated with placement of the magents in the flywheel). I also cleaned all the injectors and flushed the injector lines. The engine is running very strong, seems to be putting out alot of power and I'm impressed with the dual electronic system. My intermittant mis SEEMS to be gone, but honeslty,,,I'm not sure WHY.

I'd like to hear some input from you guys running 9:1 compression IO-360's. My friend has the same Superior IO-360 with 8.5:1 compresion and his engine really runs super smooth on one mag and one electonic ignition. My engine is nowhere near as smooth as his at cruise power settings,, even with the dual igntion. I even changed to Lord brand shock mounts with gel inserts (very little change). Is this because I'm running 9:1 compression or is it something else? I admit,, I'm a bit perplexed by this engine, but its putting out alot of power, starts easy and runs super smooth at idle and low power cruise settings. At high power and cruise power settings, best I can determine, the intermittant mis is gone, but the engine seems to "hit" hard on each ignition stroke and I'm just not sure if thats normal for a 9:1 compression engine or if I need to look further. I welcome any input you guys might offer, especially you folks running 9:1 pistons.

In order to rule out a prop imbalance, I'm going to get it dynamically balanced soon. I'm running the Hartzell Simitar prop.

Thanks,

Chad
Plano, Texas

Bring that baby over here and we'll get her balanced for you

Perceived Mis

Walt said:

Bring that baby over here and we'll get her balanced for you

Click to expand...

Walt,

Well, here I am a year later and I still have my intermittent mis. Here's my question.... Is your propeller balance equipment capable of determining which cylinder is causing my intermittent mis? Let's say my problem is an intermittent sticky valve... could your equipment see that? If so, can it narrow it down to which cylinder? My problem doesn't appear to be plugs, mags, harness, electronic ignition, fuel pressure, bad fuel servo, vaporlock, intake leaks, or valve clearance. I need to take a look at possible sticky valves. Not a STUCK valve. I'm looking for valves that might intermittently stick for a nonosecond. If this isn't my problem, I'm out of ideas. Can your equipment help? I'd prefer not to pull all four cylinders, so I'm hoping your equipment can narrow down the problem.

Best,

Chad
Plano, TX

Hi tension wires?

Not sure if you tested changed these. I might throw them all away and install new (tested) ones. I know that in the automotive world, these can be 'bad' right out of the box so they need to be tested before installation.

Please let us know how you solved this problem when that happens. Best of skill and luck.

Chad, I responded to your email but maybe you didn't get it.
Unfortunately as good as the balance equipment is, it cannot narrow it down to a specific cylinder for you.

Not sure what you've done to track this down (it can be a frustrating process when its intermittant) but from your description I would probably not suspect the valves. Sticky valves usually "stick" for much more than a "nanosecond", for such short a duration miss I would suspect an ignition fault.

Are things controlled with a keyswitch?

Vibration in a keys witch is a good call.

More so, twelve months later.... have you tried two mags timed at say 22 degrees?

Isolate the EI units and get away from high advance as well as high compression.

Seriously, worth a try and you have plent of opportunity close by. Go see Walt.

Send me some data files from your EMS if you can

Don't discount vapor lock

Chad,

In he first few hours of Phase I on my RV-8 with an IO-360 I developed that intermittent miss symptom at full power and at reduced power. . It would come and go. Data indicated it was a short duration loss of about 50 rpm or so. It felt very much like a "miss".

I first checked for fouled plugs and they were all good. I checked the fuel filter... clean as a whistle. Unfortunately, I lost all my data and was unable to analyze EGTs, etc.

During a ground run at 80 degrees OAT the engine died a few times. On the third try I was able to recover with a short burst of electric fuel pump. Watching fuel pressure "seemed" to indicate that fuel pressure loss preceded rpm loss and it appeared to cascade. The next day it was cooler outside and I left the oil access door open. It ran for 20 minutes with no issues.

As it turns out, I did such a good job of sealing the baffles after the first 4 or 5 flights that I reduced cooling air leakage on the back side. A blast tube on the fuel pump seems to have cured the problem.

Just for reference I have a 191 HP ECi XIO-360 8.9:1 with an Automotive Engineering fuel pump.

A rep with AE suggested one troubleshooting method for this type issue might be to install a clear fuel tube on the return line and look for bubbles.

Don

cfiidon said:

Chad,

In he first few hours of Phase I on my RV-8 with an IO-360 I developed that intermittent miss symptom at full power and at reduced power. . It would come and go. Data indicated it was a short duration loss of about 50 rpm or so. It felt very much like a "miss".

I first checked for fouled plugs and they were all good. I checked the fuel filter... clean as a whistle. Unfortunately, I lost all my data and was unable to analyze EGTs, etc.

During a ground run at 80 degrees OAT the engine died a few times. On the third try I was able to recover with a short burst of electric fuel pump. Watching fuel pressure "seemed" to indicate that fuel pressure loss preceded rpm loss and it appeared to cascade. The next day it was cooler outside and I left the oil access door open. It ran for 20 minutes with no issues.

As it turns out, I did such a good job of sealing the baffles after the first 4 or 5 flights that I reduced cooling air leakage on the back side. A blast tube on the fuel pump seems to have cured the problem.

Just for reference I have a 191 HP ECi XIO-360 8.9:1 with an Automotive Engineering fuel pump.

A rep with AE suggested one troubleshooting method for this type issue might be to install a clear fuel tube on the return line and look for bubbles.

Don

Click to expand...

Don,

My engine is a 9:1 compression, roller-lifter Superior IO-360 running the Bendix (Silverhawk). It has an updraft sump, but I've placed a Don Rivera 90 degree elbow on the sump to face the servo forward for ram air. The engine had the same "mis" back when I had dual mags. I then replaced one mag with electronic (Klaus) ignition, then about a year later I installed a second Klaus ignition. My problem continued. I've replaced all 8 pushrods to close my valve clearance a bit as it was found to be at the upper limits of clearance initially. I have a blast tube on the fuel pump. All fuel lines are fire sleeved and well clear of exhaust pipes. I can run the aux pump when the "mis" is very noticeable and the problem continues. I can run the engine on one ignition at a time and the "mis" continues. I've eliminated the key switch as being a potential cause by installing toggle switches for the ignition. I retained the key switch only for starting the engine. I've replaced the plugs with platinum and closed the plug gaps to a very conservative gap (don't recall what it is now, but its at the lower gap range). I've checked the airframe fuel filter as well as the screen in the servo (always clean). The Dynon EGT, CHT or fuel pressure numbers don't change one bit as a result of the mis.

Typically, the engine doesn't mis at idle; however the other day, I'd flown a short flight to get fuel. After refueling, I cranked up and found the engine to be missing same as it does at cruise power. Immediately, I turned on the boost pump,,, no change. I then ran it on individual ignitions, but it kept missing. At idle power, I can't imagine detonation being at fault. Because of the above, I believe my problem is in the valve train. I spoke with Don Rivera the other day and he agrees that a sticky valve might be worth pursuing. Don didn't feel that anything in the servo could cause an intermittent mis. By the way, I've also ran a clear fuel line from my servo to the flow divider and ran the engine for quite some time on the ground. No bubbles. The "mis" usually manifest itself at cruise power. High RPM operation is usually smooth. At idle, the engine occasionally misses, but the other day was the first time I'd ever experienced it missing at idle for a continuous duration. The mis is very intermittent (not regular), but it never stops for any length of time. Every time I fly the plane, as soon as i reduce power after the climb and the airplane settles into a normal cruise configuration, I begin to "feel" the mis. I don't particularly hear the mis. It's more of a "feel" type thing, but it's definitely the engine rather than something loose / ratteling in the engine compartment or airframe. If I go back to high RPM, I've determined that the mis is still there, but it's less noticeable. At lower RPM's it seems worse. I believe that the higher load on the propeller / engine at these lower RPM / higher power levels is simply transmitting the mis to the airframe better. High RPM's it gets less noticeable, but is still there.

When I switched to Dual electronic ignition, I had Klaus install his new Mini-Sensor ring into my existing flywheel. I then replaced the crank sensor "printed circuit board sensor" with his new Mini-sensor product. The "mis" continued. I also ripped out ALL of the wiring for the electronic ignition and replaced it with new to verify everything was properly shielded, grounded, etc. I also installed a backup battery system. If I run the engine on one ignition using the backup battery, the mis continues. Recently, I replaced my alternator with a Plane Power unit for Over-voltage protection which I previously did not have. Still misses. I removed the interconnect feature from the dual electronic system so that I would truly have two completely separate ignition systems that aren't connected in any way (except for battery power). Each ignition uses separate crank sensors. This made no difference. Still misses. One ignition fires the upper plugs and the other fires the bottom plugs. Like I said, the mis continues no matter which set of plugs I fire, so this rules out a faulty ignition lead (unless I have a bad one on the top AND the bottom. The oldest ignition wire I have has 200 hrs. on it (same as the engine). I truly don't believe that ignition is the problem, even though I agree that my mis feels like an ignition problem. As you can see, I've spent considerable time and money on chasing an ignition issue.
I've also changed my air induction a couple of times thinking that turbulence in the intake system might be my problem. I'm now running a large cone filter that's inside a pressurized air box (Similar to the Sam James unit, but I'm using a larger filter than he uses for the IO-360).

I've cleaned injector nozzles numerous times using gun bore cleaner. They're spotless when I'm done, but the engine still misses. I've flushed the flow divider lines as well as the flow divider itself with the top off. I've disassembled the flow divider looking for trash or friction in the porting assembly,,, nothing found, (but I was sure not to change orientation of the diaphram assembly during reassembly).

I've also disassembled, cleaned, and reassembled four (one side of the engine) of the roller lifter assemblies (in place, on the engine). This wasn't fun, but was do'able. Didn't really find anything such as trash in the lifter bodies that would cause my problem, but thought I'd mention it here. I had the folks at Superior (Bill) show me how to do this. I never did get around to doing the other side, but I might disassemble and inspect the other four while I have the cylinders off. I think it might be easier to do them with the cylinders out of the way.

What am I missing (no pun intended)? I'm about to pull all four cylinders to check valve guides for one that might have friction in it or seems sticky.

I have a hangar partner with an RV-7A using the same engine, prop, servo combination. He's not using the 90 degree elbow, his engine has 8.5 compression pistons, and he's running one mag and one Klaus electronic ignition. His engine runs like a dream. Totally smooth,,, so I know how the engine SHOULD run and I'm willing to accept that the higher compression pistons MIGHT run a bit rougher, but my engine definitely has a "mis" compared to his.

Suggestions? And by the way, I seriously appreciate everyone's input thus far.

Best,

Chad

rocketbob said:

Are things controlled with a keyswitch?

Click to expand...

Nope, not any more. Rocker switches. Didn't fix my problem.

Chad

I went back through the thread and I can not see anywhere that you actually checked the valves stems and guides. You mention that you are going to pull the cylinders to check the valve guides. It is not necessary to pull the cylinders to do this job. The old rope trick, ask any mechanic, will allow you to drop a valve and check the guides.

I would retard the timing a bit and see if that has any effect before I would start chasing down the valve sticking rabbit hole.

Tom Martin said:

I went back through the thread and I can not see anywhere that you actually checked the valves stems and guides. You mention that you are going to pull the cylinders to check the valve guides. It is not necessary to pull the cylinders to do this job. The old rope trick, ask any mechanic, will allow you to drop a valve and check the guides.

Click to expand...

Tom,

I've heard about the "rope trick" for years, but I've never done it myself. I read an article about it this afternoon, and I'll definitely give this a try. I don't see any reason I can't check valve stem/guide clearance via this method and feel satisfied with the result. Thanks for the reminder. You probably just saved me quite a bit of time. I just wish I already knew which cylinder is causing my problem. Hey, maybe it's more than one cylinder. Honestly, I don't care if I have to take a look at all eight valves if the end result will fix my problem. I'm optimistic!! Walt is on board with this idea as well, so that's good enough for me.

Best,

Chad

rocketbob said:

I would retard the timing a bit and see if that has any effect before I would start chasing down the valve sticking rabbit hole.

Click to expand...

The way that the new mini-sensor is mounted doesn't make retarding the timing very easy, but I can probably shim it somehow or another. 'll give it a try if I don't have any luck with finding a tight or sticky valve. At idle however, I wouldn't think that the timing on the electronic ignition would be much advanced. The other day, the engine was missing at idle on the ground (on each individual (and independent) electronic ignition), so I doubt timing is my problem unless both Klaus ignitions are doing something funky. Klaus installed the mini-sensor ring into my flywheel personally, so it should be right. Looked right to me before installation onto the engine.

Best,
Chad

Idle is where the timing advances the most and if its too far advanced it may be firing well before TDC. Its a lot of work to pull the exhaust off, and much more work to ream the guides. Eliminate things in order of difficulty to fix. That said you could easily pull intake tubes off and check for any valve discoloration on the intake side of things. If the intake valves are sticking open then there will be a lot of soot and carbon on them.

Having been down the sticking valve path recently...

I didn't re-read all posts in this thread before starting this reply. Do you have a 4 cylinder engine monitor? Every time I experienced what in my case was very rough running, the offending cylinder (#2, not that it matters) would make itself known with decreased cylinder head temp and increased exhaust gas temp. When it got really bad, both would go into the toilet- the cylinder would go dead. In all but one case it "fixed" itself before I could get on the ground.

After trying everything else I could think of- going through fuel injection, ignitions, plugs, wires, hose routing, etc, I bought measuring equipment and a valve spring compressor from Aircraft Spruce and performed the "wobble test" on #2 exhaust valve. Even though it felt smooth and, to me, slightly loose, a local mechanic stopping by estimated it to be tight based on feel. This being the first one I'd ever messed with, I had no yardstick for comparison.

According to the Lycoming wobble test, the valve was indeed slightly tight (.013" of wobble, slightly below the .015" minimum). The whole test seems sorta bogus to me, but again I have no basis for argument since I have never been inside a Lycoming before.

Instead of using the "rope trick" I used compressed air with a spark plug adapter, same as I've done a zillion times to replace valve springs on car engines, to get the valve spring off. I bought the correct reamer (.4995" if memory serves) for 20 bucks at a local machine tool supplier. Ran the thing through the guide, cleaned up, fished the valve out of the cylinder and reassembled. That was almost 40 hours ago. It's run flawlessly ever since. With proper tools in hand I could do the whole job now in an hour. Though I'd be delighted if I don't have to...

Oh yeah, worth noting: my engine is a Superior IO-360, parallel valve, 8.5:1 pistons, vertical draft fuel injection, dual Light Speed Plasma III ignitions, roller cam, P/A Silverhawk fuel injection, etc, etc.Bought new from Superior in January 2007, sat pickled until first start in May of this year. The first misfire event occurred when the engine had 5 hours on the clock.

Lars said:

Having been down the sticking valve path recently...

I didn't re-read all posts in this thread before starting this reply. Do you have a 4 cylinder engine monitor? Every time I experienced what in my case was very rough running, the offending cylinder (#2, not that it matters) would make itself known with decreased cylinder head temp and increased exhaust gas temp. When it got really bad, both would go into the toilet- the cylinder would go dead. In all but one case it "fixed" itself before I could get on the ground.

After trying everything else I could think of- going through fuel injection, ignitions, plugs, wires, hose routing, etc, I bought measuring equipment and a valve spring compressor from Aircraft Spruce and performed the "wobble test" on #2 exhaust valve. Even though it felt smooth and, to me, slightly loose, a local mechanic stopping by estimated it to be tight based on feel. This being the first one I'd ever messed with, I had no yardstick for comparison.

According to the Lycoming wobble test, the valve was indeed slightly tight (.013" of wobble, slightly below the .015" minimum). The whole test seems sorta bogus to me, but again I have no basis for argument since I have never been inside a Lycoming before.

Instead of using the "rope trick" I used compressed air with a spark plug adapter, same as I've done a zillion times to replace valve springs on car engines, to get the valve spring off. I bought the correct reamer (.4995" if memory serves) for 20 bucks at a local machine tool supplier. Ran the thing through the guide, cleaned up, fished the valve out of the cylinder and reassembled. That was almost 40 hours ago. It's run flawlessly ever since. With proper tools in hand I could do the whole job now in an hour. Though I'd be delighted if I don't have to...

Oh yeah, worth noting: my engine is a Superior IO-360, parallel valve, 8.5:1 pistons, vertical draft fuel injection, dual Light Speed Plasma III ignitions, roller cam, P/A Silverhawk fuel injection, etc, etc.Bought new from Superior in January 2007, sat pickled until first start in May of this year. The first misfire event occurred when the engine had 5 hours on the clock.

Click to expand...

Our engines are identical except for the pistons (9:1). Lars, did your engine ever act like mine. An intermittent shudder, but never enough to make you think it might quit? Clearly yours was worse than mine, but did it ever do an intermittent shudder? I keep having folks tell me that valves either stick or don't stick, nothing intermittent like mine. Also, I've NEVER seen my problem show up on the engine monitor in any way (Dynon). Also, my "shudder" virtually never goes away in cruise flight, but yet, nothing shows on the engine monitor. Weird!!

Thanks for the information. All good to know!

Chad

Speeddog7 said:

Our engines are identical except for the pistons (9:1). Lars, did your engine ever act like mine. An intermittent shudder, but never enough to make you think it might quit? Clearly yours was worse than mine, but did it ever do an intermittent shudder? I keep having folks tell me that valves either stick or don't stick, nothing intermittent like mine. Also, I've NEVER seen my problem show up on the engine monitor in any way (Dynon). Also, my "shudder" virtually never goes away in cruise flight, but yet, nothing shows on the engine monitor. Weird!!

Thanks for the information. All good to know!

Chad

Click to expand...

Yeah, it was intermittent. Eventually though I was able to get it to misbehave on command. Do a full power climb for a few thousand feet, then throttle back. At first it would be subtle, then get worse. When it was bad, basically running on 3 cylinders, it shook like a paint mixer- or more frighteningly, like it was shedding parts. By leaning aggressively (like, oh, until the engine quit) then bringing it back, I could get it to stop. Usually.

That said, if you really have a miss I would expect you would see something on an engine monitor, though it may not be dramatic. If it really is missing, it's not developing full (or same as other cylinders) power- CHT, EGT or both should change on the offending cylinder(s). But maybe I'm missing (pardon the pun) something.

Also, if you haven't done so already, get the prop balanced. Mine wasn't that far out according to the numbers, but I was impressed at how much smoother it ran after balancing. What I assumed to be normal roughness turned out not to be.

Lars said:

Yeah, it was intermittent. Eventually though I was able to get it to misbehave on command. Do a full power climb for a few thousand feet, then throttle back. At first it would be subtle, then get worse. When it was bad, basically running on 3 cylinders, it shook like a paint mixer- or more frighteningly, like it was shedding parts. By leaning aggressively (like, oh, until the engine quit) then bringing it back, I could get it to stop. Usually.

That said, if you really have a miss I would expect you would see something on an engine monitor, though it may not be dramatic. If it really is missing, it's not developing full (or same as other cylinders) power- CHT, EGT or both should change on the offending cylinder(s). But maybe I'm missing (pardon the pun) something.

Also, if you haven't done so already, get the prop balanced. Mine wasn't that far out according to the numbers, but I was impressed at how much smoother it ran after balancing. What I assumed to be normal roughness turned out not to be.

Click to expand...

Thanks Lars. I'm going to go down the sticky valve route first. I think I'd like to look at something other than ignition and fuel at this point. I need a change of pace and quite possibly the sticky valve theory might be worth pursuing..... will let you know.