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Rough engine at 1500-1700 rpms

sirlegin

Well Known Member
This is an injected Lycoming OF-320. Catto 3 blade fixed pitch. 10 hours
The engine starts and idles nicely, however both on the ground and in the air when the throttle is advanced to 1500rpm the engine becomes rough and does not respond well to the throttle until 1800 rpms are reached and then the engine will play catch up and go to 2000 rpms.
While at 4500 ft and after about 35 minutes of flight I could get no rpm's above idle. I switched tanks from left to right with the boost pump on and after a little while, varying throttle settings, the rpm's came back. I had switched the tanks after 30 minutes from right to left about 5 minutes earlier. I think this was more coincidental rather than significant. When I did have rpm's I was also getting backfires. There was no holding a set rpm and surges of 1 to 300 rpm on any setting above 1200 rpm was the norm. There was alot of throttle movement with no reaction from the engine.
The engine never made full power and at best WOT at cruise was 2500 rpm.
I ran it up back at the hangar and the same dead zone at 1500 to 1700 rpm was evident but none of the other inflight symptoms.
I have changed the injectors, sealed induction leaks, cleaned fuel filters and have run out of idea's.
Below is a graph of the MAP vs engine rpm's and there is a definate lack at the dead zone area. 1500-1700 rpm's.
I have a K&N filter which was recently cleaned and re oiled, perhaps too much oil?
Any thoughts would be greatly appreciated.



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Rough engine

My engine on 1st start did not respond well to throttle, was rough at and above idle to near full throttle and backfired. Idle mixture was too lean. Simple to adjust.
 
Nigel.

First thing----DO NOT FLY till you figure out your fuel flow problem.
You are asking for trouble.
There are plenty of guys out there that can help you.
I would change the filter to paper if you can. Don't know how much oil
you used but don't think that is the problem.

Pull off fuel line to engine and do a fuel flow test.
Check the mixture lever and make sure it is hitting the stops.
Do you run it full rich?? or are you leaning??
What is your egt's showing 1200-1300??
CHT's300-400??

Give Walt a call if this doesn't help.
 
Definately not flying until the problem is resolved.
During the flight when things started going horribly wrong, average CHT was 357, EGT 1412. After flight before shut down:
CHT's 1)330 EGT 1377
2)282 1374
3)342 1223
4)308 1423
The fuel burn for the hour was 5.5 gph so possibly quite lean or fuel starvation?
This is a FADEC run engine so no mixture adjustments available by pilot.
I will be calling on Walt who helped me with pre certification checks etc, (Thanked on the mothership 1st flight note) although he is not familiar with FADEC systems.
 
Nigel,

Walt is your man.

It does look like it is running lean. I would do that
fuel flow test and go from there.

Glad your not getting air under the wings.
You had me scared for a second.

Boomer
 
Will do Bruce and thanks.
However, how would the fuel flow affect the MAP graph with the loss of non ambient pressure at 1500+ rpm per the chart?
 
With a FADEC you have other things that may go wrong. Since you can duplicate the problem on the ground, I suggest just one change at a time then see if it works properly.
 
leaks at the fittings

My friend has an injected O-320 in his 9A. He had low fuel pressure and much air the lines due to loose fuel line fittings at the tanks. He tightened every fitting in the fuel systems and all was well for the last 2 years. However it seems the problem may be returning as he felt a bit of roughness on a recent flight. I mentioned he should closely inspect all the flares on the fuel lines. Perhaps replace the lines with the Bonaco braided product.
 
Nigel,
I'll have to get up to speed on the Aerosance FADEC system as yours is the first one I've encountered. If you have the manual in PDF send me a copy and I'll have a look at it, then we'll go from there.
Walt
 
If it were mine, I'd just bite the bullet now and install an AFP system with mags or EI, reliability is the name of the game in my book and I don't think you're ever going to have a very high comfort level with the Aerosance system. Another great idea that never worked out for whatever reason.
Just my 2c
 
I had a dead plug in one cylinder one time and it gave a rough engine with back fires. If you lose egt on one cylinder when you do a mag check, that could be your problem.

I'm running an io360 and the only way I can get to 5.5 gallons per hour is lean the **** out of it.
 
Posted for a buddy.

"Food for thought.
I have found more problems with dirty injectors than anything. On my 4 I had a mag drop, had the mags rebuilt, had the injection servo rebuilt, flow tested and the spider overhauled. It was a piece of **** that looked like a hair in one of the injectors. Sense I have pulled all the injectors prior to first start, turned the boost pump on and let fuel flow into rags a the end of the injection lines, then looked through the injectors, and blew them out with air. Dirty injectors do all kinds of goofy things and all different RPM's, it's a simple task, lets start with the simple stuff first and not get to technical, it's expensive. What is an "OF-320?", I had an IO-320 with a Bendix injection.

Merry Xmas"
 
Just an FYI, the "OF" designates the FADEC system, there are absolutely zero similarities between the Aerosance FADEC and a regular FI/IGN system.
 
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What is your fuel pressure? I had a very similar problem with my IO-360 prior to first flight. After talking to Lycoming Tech Support, he said it must be a leaky fitting in front of the fuel boost pump. I complained that there were were no leaks there, but he said not to expect leaks since the fuel system was "sucking" fuel rather than moving it upstream under pressure. I redid all the aluminum fuel lines from the selector to the boost pump, and it fixed the problem.

-John Banister
 
I would look very close at #3 cylinder. Its posted EGT was very low. I believe it is on the lean side of peak which will cause hesitation and miss along with low power. Possible culpret would be an intake tube leak either at the sump or cylinder. Also look at the injector on #3 for blockage....clean the injector for good measure. I want to qualify this by saying I know nothing about the FADEC system you are using.:eek:
Dave Swift Driver....and A&P
 
Nigel,
I'll have to get up to speed on the Aerosance FADEC system as yours is the first one I've encountered. If you have the manual in PDF send me a copy and I'll have a look at it, then we'll go from there.
Walt

Walt, didn't I send you a pdf copy of the Aerosance FADEC manual??? Maybe not, I sent so many out that I could be wrong. I no longer have the manual on my computer.


If it were mine, I'd just bite the bullet now and install an AFP system with mags or EI, reliability is the name of the game in my book and I don't think you're ever going to have a very high comfort level with the Aerosance system. Another great idea that never worked out for whatever reason.
Just my 2c

Nigel,

After experiencing a major inflight fault with my FADEC system, I did exactly what Walt recommended. I installed an AFP system with Slick mags. However, don't throw in the towel yet. The folks at TCM are still giving limited technical support to Aerosance FADEC Systems. Give them a call. If you have the fault codes they can analyze the fault.

You also mentioned that you changed the injectors. They are a very fragile component extremely suseptible to FOD. They can only be cleaned by the factory in essentially sterile conditions. It is very easy to contaminate an injector during installation.

Also ensure that the electro-magnets that slip over each injector body is properly seated and torqued. Also check the continuity of those wires leading to the magnets.

Good Luck,
 
I had similar problems with Aerosance FADEC on my engine run on a dyno. After a couple of tries by changing injectors and fuel pressures I removed the FADEC and fitted AP fuel injection and Plasma III ignition systems. Not sorry I did that. I think what you describe is common problem with Aerosance Fadec system.
A freind of mine here in Oz is running that system and it was not until he changed the computers that it ran in an acceptable manner. Even now every now and then in flight, he will have to re-boot one/both of the computers because a fault light shows up or starts running rough or fuel flow goes UP.
Even when running ok the fuel burn is much higher than non FADEC aircraft.


This is only my opinion, but get rid of the Fadec now. You will save yourself a lot of trouble and heartache
 
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