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Old 12-14-2014, 05:04 PM
redwoodcstrvr redwoodcstrvr is offline
Join Date: Dec 2008
Location: Mckinleyvill, CA
Posts: 33
Default Cold cylinder/no egt/low cht

I have a factory new YIO-320 Lycoming engine installed on my RV-9A with just over 50 hours. My fuel servo is a Precision Airmotive Silver Hawk. During the early hours of Phase One flight testing I noticed that at reduced throttle settings/idle, in the air or on the ground, I would hear routine "popping" sounds from the exhaust. Engine performance was fine at higher throttle settings and full power was as advertised by Lycoming. Adjusting the idle mixture and aggressive leaning seemed to reduce, but not totally eliminate, the instances of popping. Fast forward to yesterday's start and taxi and I found EGT and CHT on #2 cyl were near zero on my EMS. Taxied back to the hangar, shut down, removed the cowling and found by placing my hand on each cyl. valve cover that the #2 cyl. was warm while 1, 3, and 4 were too hot to touch. This indicated to me that the EMS indications for that cyl were correct and that it was not producing power. I completed the first annual inspection in Sep. and compression was 75PSI on all cylinders. Mag timing and spark plugs were checked and tested as well. I believe the problem of low power "popping" is related to the now cold cylinder issue and lies with fuel injection to that cyl. Any ideas on a course of action in trouble shooting the problem would be greatly appreciated.
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Old 12-14-2014, 05:19 PM
N427EF N427EF is offline
Join Date: Oct 2005
Posts: 1,617
Default Just a guess

You might have a partially clogged fuel injector.

A piece of debris, possibly something that came loose from the tanks or fuel lines and made its way all the way past fuel strainer filter and finger strainer
in the injection servo.
A flow test would reveal such a problem.
Next best idea is a bad spark plug.
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Running on 91 Octane E10 mogas since 2011
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Old 12-14-2014, 05:21 PM
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LifeofReiley LifeofReiley is offline
Join Date: Jan 2005
Location: Round Rock, TX
Posts: 3,779

Sounds like you might have a sticky valve on that cylinder. With the low time, I bet you have been running rich on the mixture.
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Last edited by LifeofReiley : 12-14-2014 at 05:30 PM.
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Old 12-14-2014, 05:35 PM
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ColoRv ColoRv is offline
Join Date: Apr 2012
Location: Tampa (BKV)
Posts: 926

I had similar recently, turned out to be sticking valves. If you just changed your oil...especially if you just changed it to something you had not been using before....change it back and see if the problem goes away. Either way, next time it does it, shut down while the cylinder is not firing and rotate the prop through 4 compression cycles...if one of them is missing...that's a stuck valve.

Valves aside, I would look for crud in an injector. Pretty common on new systems.

As for the popping, have you performed a high/low manifold pressure flight test to check for induction leaks yet? That fixed my popping. These two issues may not be related...don't assume they are. If it's a bad induction leak they could be the same issue though.
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Last edited by ColoRv : 12-14-2014 at 11:04 PM.
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Old 12-14-2014, 05:48 PM
Petedfl12 Petedfl12 is offline
Join Date: Sep 2011
Location: Tampa FL
Posts: 44

Sounds to me like you may have a loose hose connection between your intake pipe and the small rubber hose connecting to the manifold - on the #2 cyl. Check the hose connection (clamps) between the intake pipe and the manifold for proper seal and security .
Hope that's all it is - good luck.
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Old 12-18-2014, 10:57 AM
redwoodcstrvr redwoodcstrvr is offline
Join Date: Dec 2008
Location: Mckinleyvill, CA
Posts: 33
Default Thanks

Appreciate all the comments. Will check the fuel nozzle for a blockage first then for a possible stuck valve.
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