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Srange EGT and power loss on Cylinder 1, IO-320

edclee

edclee

Well Known Member
Patron
Coming back from Savanah GA today just leveling at 9500' I experienced a power loss and rough running on the IO-320 in my RV9A. Looking quickly at the engine monitor I could see the EGT on #1 headed to zero. All other EGTs good. After doing some troubleshooting I discovered that richening the mixture substantially cause the engine power to come back and #1 EGT coming back up but it kept going when reaching the other EGTs it kept going and went above 1500, 300 degrees above the other three. Full rich brought the EGT back to about 1450 and engine running OK, but other EGTs much lower by about 300 degrees. I started heading for a nearby airport and dropping altitude. About 3500' #! EGT started coming down suddenly and engine running very well. EGTs now all equal. All good, CHT and EGT exactly where they should be. I releaned the engine and all remained good. I decided to climb and keep an airport in gliding range and continued the trip home about 45 minutes. Engine continued to run properly. My conclusion is that a something was blocking either the injector or flow divider to #1 and then either passed or dissolved

What do you think?
Ed.

PS, Edit, forgot to mention I had leaned to about 20 degrees LOP at 9500, which is normal for me and never an issue prevously. Rolling back the mixture to well ROP did NOT bring the #1 EGT back up from zero nor did the engine roughness change until the mixture was richened almost back to full rich at 9500.
 
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You picked up a little piece of crud blocking the injector for #1, and it worked itself free. The extra fuel that could not go into #1 was being distributed to the other 3 cylinders.
 
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edclee said:
Coming back from Savanah GA today just leveling at 9500' I experienced a power loss and rough running on the IO-320 in my RV9A. Looking quickly at the engine monitor I could see the EGT on #1 headed to zero. All other EGTs good. After doing some troubleshooting I discovered that richening the mixture substantially cause the engine power to come back and #1 EGT coming back up but it kept going when reaching the other EGTs it kept going and went above 1500, 300 degrees above the other three. Full rich brought the EGT back to about 1450 and engine running OK, but other EGTs much lower by about 300 degrees. I started heading for a nearby airport and dropping altitude. About 3500' #! EGT started coming down suddenly and engine running very well. EGTs now all equal. All good, CHT and EGT exactly where they should be. I releaned the engine and all remained good. I decided to climb and keep an airport in gliding range and continued the trip home about 45 minutes. Engine continued to run properly. My conclusion is that a something was blocking either the injector or flow divider to #1 and then either passed or dissolved

What do you think?
Ed.

PS, Edit, forgot to mention I had leaned to about 20 degrees LOP at 9500, which is normal for me and never an issue prevously. Rolling back the mixture to well ROP did NOT bring the #1 EGT back up from zero nor did the engine roughness change until the mixture was richened almost back to full rich at 9500.
Click to expand...

My first guess would not be an injector from that description. My money is on ignition issue affecting both plugs in #1 or a piece of debris keeping one of the valves from closing for a few seconds before clearing tself. Change of symptoms tied to moving mixture knob likely coincidental. I can’t imagine debris in an injector that fully blocked fuel and then cleared itself a few seconds later, though i am sure it is possible.
 
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Strange EGT, Loss of Power

oaklandaviator said:
Sounds like a sticking valve to me.
Click to expand...

I considered the stuck valve and thought of that first, but when I discovered that going full rich re-established power (this is after maybe 5 minutes of the power loss and loss of EGT), I was able to reproduce the problem reliably by trying to re-establish leaner mixture (still at 9500). As I leaned more toward the correct fuel flow for that altitude, the #1 EGT went higher and higher and then the cylinder would quit producing power and the EGT would drop immediately. I could play the mixture control and bring that cylinder back to power production or make it quit again (around 1550F EGT). This took place over several minutes, not seconds. Finally after maybe 12 to 15 minutes, the EGTs and power returned to normal and stayed that way for the additional 45 minutes to home.

I dont see how a stuck valve could behave in this way, but I am not certain.
Ed
 
Plug

Hmmm. Interesting. I've had something similar happen at altitude with dirty plugs. Harder to make a spark at high altitude and lean mixtures. Try cleaning your plugs and see if that helps. After reading your expanded description I'm leaning toward that.
 
a plugged injector should either force 25% more fuel to the other open injectors, driving a noticeable EGT change to those 3, OR reduce overall fuel flow by 25%, which will show up on the EMS.

Did you see a change in FF or a change in EGT on the "good" 3?
 
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edclee said:
I considered the stuck valve and thought of that first, but when I discovered that going full rich re-established power (this is after maybe 5 minutes of the power loss and loss of EGT), I was able to reproduce the problem reliably by trying to re-establish leaner mixture (still at 9500). As I leaned more toward the correct fuel flow for that altitude, the #1 EGT went higher and higher and then the cylinder would quit producing power and the EGT would drop immediately. I could play the mixture control and bring that cylinder back to power production or make it quit again (around 1550F EGT). This took place over several minutes, not seconds. Finally after maybe 12 to 15 minutes, the EGTs and power returned to normal and stayed that way for the additional 45 minutes to home.

I dont see how a stuck valve could behave in this way, but I am not certain.
Ed
Click to expand...

With that more detailed description (should have led with that), I would be looking for a bad plug (likely fouling) or wire on #1. That description could also describe an exhaust valve that was not fully closing (debris between valve / seat or sticking in guide).

I don't understand how people looking for diagnostic help can have this level of detail and choose not to share it when their goal is getting more troubleshooting help.
 
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Loss of Cyl 1, exhaust valve?

lr172 said:
My first guess would not be an injector from that description. My money is on ignition issue affecting both plugs in #1 or a piece of debris keeping one of the valves from closing for a few seconds before clearing tself. Change of symptoms tied to moving mixture knob likely coincidental. I can’t imagine debris in an injector that fully blocked fuel and then cleared itself a few seconds later, though i am sure it is possible.
Click to expand...

It kinda acted like that except that I could reproduce the problem. Richening caused the EGT to come back up and then leaning it caused it to crash again. I did this several times and the situation continued for about 12 to 15 minutes before suddenly going away for the next 45 minutes until I got home.
Ed
 
Here were the symptoms of a clogged injector of my buddies IO-360 Cozy MKIV when we were out flying instrument approaches last year:
There was a pretty fast noticeable loss of power, then the engine started to shake violently. Thought at first we threw a prop blade it was so bad. (MT 3 blade). CHT's went down significantly on three cylinders as one cylinder died off completely. (G3i ignition system running auto plugs.) On the ground I started to pull plugs. The spark plugs on the three cylinders that were still firing were covered in soot and somewhat wet. The dead cylinder plugs were fairly dry. I found something that was white in color fully obstructing the dead cylinder's FI restrictor. Never did find the piece after I picked it out so I have no idea what it was. It was not Teflon tape as we did not use any during the build. The fuel pump and filter are AFP. All FI nozzles and restrictors were soaked and cleaned using Hoppe's #9. Engine has been running like it should since the injector cleaning.
 
AFP says likely injector problem

9GT said:
Here were the symptoms of a clogged injector of my buddies IO-360 Cozy MKIV when we were out flying instrument approaches last year:
There was a pretty fast noticeable loss of power, then the engine started to shake violently. Thought at first we threw a prop blade it was so bad. (MT 3 blade). CHT's went down significantly on three cylinders as one cylinder died off completely. (G3i ignition system running auto plugs.) On the ground I started to pull plugs. The spark plugs on the three cylinders that were still firing were covered in soot and somewhat wet. The dead cylinder plugs were fairly dry. I found something that was white in color fully obstructing the dead cylinder's FI restrictor. Never did find the piece after I picked it out so I have no idea what it was. It was not Teflon tape as we did not use any during the build. The fuel pump and filter are AFP. All FI nozzles and restrictors were soaked and cleaned using Hoppe's #9. Engine has been running like it should since the injector cleaning.
Click to expand...

Thanks for that. Of course if it had not cleared up I am sure the cause would be more obvious since whatever it was would still be in that condition when I got back home. Fortunately or unfortunately, the problem is now gone (for now). I talked with Kyle at Airflow Performance and explained the problem and he said it was unlikely a stuck or partially open valve, but most likely something in the flow divider or injector restriction. I have .022 restrictors in my engine.
Ed
 
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