Cold Cylinder Mystery

[Yetti]

But they are brown and boring and don't look as cool as finely routed stainless outer braid.   My Dad was engineering in a ship yard.   a boats engine room full of stainless braid with everything routed and ship shape was a thing of beauty

[jetdriven]

No requirement for a fire sleeve in boats. I toured the SpaceX facility in Hawthorne.  Look there brown silicone 124J hoseson that rocket motor. This one has flown into space and dunked in salt water but there it is.  I said read that tag, does it say 124J00-8CRxxxx....?   Well yes it does, I didn't know they put space ship hoses on small piston planes. I think it was the other way around. And oh btw those adel WD clamps are too big. 

[Will.iam]

Well this post is the closest i have found to my new development from my last trip. I had GAMI injectors installed at my last annual. All same size as i didn’t have Fuel flow recording capability on my jpi-700 that got added this annual too. After test flights my number 3 cyl was the leanest which i knew before the fuel flow recorder because it was always the first to peak on a gami lean test. So received a bigger fuel flow injector but number 3 was still too lean. Flew up to ada ok and GAMI installed a bigger injector to #3 cyl and finally #3 peaked in the middle of the pack and brought my spread down to .2 i was happy engine ran  noticeably smoother and cooler on the way home. We go on a trip to KPSO and on the way uploaded 97 gallons of fuel at Olney airport that i suspect had a little water in the fuel even though i drain both stumps and saw no water we only let the plane sit for 10 mins before i had tested for water and maybe the water had not settled out of the fuel yet because we took off on the right tank that was fueled after the left tank and flew for 2 hours then when i switched tanks the engine  stumbled For 10 seconds before resuming normal running. I chalked up the problem to water settling out of the fuel for the 2 hours before i switched tanks. No other problems until we goto leave today i start the airplane and lean Aggressively like i do at sealevel but number 3 cyl is slow to warm up. I’m thinking it’s due to being at 7200ft and 40 degrees outside. when i runup for mag check and full power for takeoff #3 cyl falls inline with the other cyl and the flight home for the next 3 hours is fine in fact the engine is running very nicely LOP with cool cyl temps and very even. I do a 25” MP pressure descent to pattern altitude and then pull back to 20” to slow drop the gear and on base reduce to 15” or so then i see #3 cyl go cold and rough engine vibrations. I add some power and it smoothes out as i come in to land i pull power to idle but the engine will not go below 1200rpm i use up all the runway to stop to avoid flat spotting a tire but even turning around to backtaxi the engine is still running at 1200rpm with #3 cyl cold and engine is rough. I do a runup to 2000rpm #3 cyl starts warming back up and engine smooths out but bringing back to idle it again only goes down to 1200rpm.  I pulled the engine data and you can see the slow to warm #3 cyl at start but the engine idled at 800 rpm so something changed in flight on the way home that caused the idle to not go below 1200. Any ideas? And is it related to the #3 cyl going cold?

i just had new wiring harness and surefly installed last annual. Also had mag overhauled. I have tempest sparkplugs with less than 110 hours on them since new. I don’t think it’s a spark issue. Maybe there was more than water in that gas? Or maybe it wasn’t water but something comming loose in the fuel line? I’m thinking something happened to the number 3 injector since that is the last thing to be changed for the cold cyl issue but at a loss for what would cause the high idle. Can a faulty fuel flow divider cause this? Also i thought the injectors were to be torqued 30-35 inch pounds? Gami torqued to 60 inch pounds. Which is correct?

 

here is the data for flt

https://apps.savvyaviation.com/flights/5426466/05d1d077-0983-4b68-a813-4a2a8d2ba360

 

[N201MKTurbo]

2 hours ago, Will.iam said:

Well this post is the closest i have found to my new development from my last trip. I had GAMI injectors installed at my last annual. All same size as i didn’t have Fuel flow recording capability on my jpi-700 that got added this annual too. After test flights my number 3 cyl was the leanest which i knew before the fuel flow recorder because it was always the first to peak on a gami lean test. So received a bigger fuel flow injector but number 3 was still too lean. Flew up to ada ok and GAMI installed a bigger injector to #3 cyl and finally #3 peaked in the middle of the pack and brought my spread down to .2 i was happy engine ran  noticeably smoother and cooler on the way home. We go on a trip to KPSO and on the way uploaded 97 gallons of fuel at Olney airport that i suspect had a little water in the fuel even though i drain both stumps and saw no water we only let the plane sit for 10 mins before i had tested for water and maybe the water had not settled out of the fuel yet because we took off on the right tank that was fueled after the left tank and flew for 2 hours then when i switched tanks the engine  stumbled For 10 seconds before resuming normal running. I chalked up the problem to water settling out of the fuel for the 2 hours before i switched tanks. No other problems until we goto leave today i start the airplane and lean Aggressively like i do at sealevel but number 3 cyl is slow to warm up. I’m thinking it’s due to being at 7200ft and 40 degrees outside. when i runup for mag check and full power for takeoff #3 cyl falls inline with the other cyl and the flight home for the next 3 hours is fine in fact the engine is running very nicely LOP with cool cyl temps and very even. I do a 25” MP pressure descent to pattern altitude and then pull back to 20” to slow drop the gear and on base reduce to 15” or so then i see #3 cyl go cold and rough engine vibrations. I add some power and it smoothes out as i come in to land i pull power to idle but the engine will not go below 1200rpm i use up all the runway to stop to avoid flat spotting a tire but even turning around to backtaxi the engine is still running at 1200rpm with #3 cyl cold and engine is rough. I do a runup to 2000rpm #3 cyl starts warming back up and engine smooths out but bringing back to idle it again only goes down to 1200rpm.  I pulled the engine data and you can see the slow to warm #3 cyl at start but the engine idled at 800 rpm so something changed in flight on the way home that caused the idle to not go below 1200. Any ideas? And is it related to the #3 cyl going cold?

i just had new wiring harness and surefly installed last annual. Also had mag overhauled. I have tempest sparkplugs with less than 110 hours on them since new. I don’t think it’s a spark issue. Maybe there was more than water in that gas? Or maybe it wasn’t water but something comming loose in the fuel line? I’m thinking something happened to the number 3 injector since that is the last thing to be changed for the cold cyl issue but at a loss for what would cause the high idle. Can a faulty fuel flow divider cause this? Also i thought the injectors were to be torqued 30-35 inch pounds? Gami torqued to 60 inch pounds. Which is correct?

 

here is the data for flt

https://apps.savvyaviation.com/flights/5426466/05d1d077-0983-4b68-a813-4a2a8d2ba360

 

Did you try leaning the mixture to get it to idle? Its possible that that the big injector is supplying too much fuel at idle.

I always heard that the 231 engine had airflow issues, which will be different at high power and idle. You have the newer engine which has much better airflow than the earlier engines.

[Will.iam]

8 hours ago, N201MKTurbo said:

Did you try leaning the mixture to get it to idle? Its possible that that the big injector is supplying too much fuel at idle.

I always heard that the 231 engine had airflow issues, which will be different at high power and idle. You have the newer engine which has much better airflow than the earlier engines.

True the #3 cylinder could be receiving too much fuel and it probably is but the engine running at 1200 rpm when i have the throttle all the way back is still a mystery as i would think #3 not working the engine would idle at less rpm or not idle at all instead of racing at 1200. 

[N201MKTurbo]

1 hour ago, Will.iam said:

True the #3 cylinder could be receiving too much fuel and it probably is but the engine running at 1200 rpm when i have the throttle all the way back is still a mystery as i would think #3 not working the engine would idle at less rpm or not idle at all instead of racing at 1200. 

It must have an intake leak.

[Will.iam]

Well i pulled off the cowl and noticed an oily splatter where i circled in red that wasn’t there before it’s dark greenish in color any ideas what it is or where it came from?

[Will.iam]

Mystery solved!

the nut on the intake flange had come loose which is what the greenish splater I suspect came from and i think enough air was getting through that flange to allow all the cylinders to get more air resulting in the 1200rpm. Once i tighten down the nut and test ran the engine everything was back to normal. It was this nut circle in red that was loose. I double checked all the other flange nuts and they were tight. 
 

on a different note i did a boroscope and the valves looked fine but i noticed oil streak lines down the side of the cylinder wall is this a sign of Worn piston oil ring?

 

[Will.iam]

Well even though i got the idle back to normal and no more green splatter from tightening down the loose nut on the flange the #3 cyl was still showing cooler than other cyl at idle and a suggestion was made that the induction gasket could be damaged or dry cracked. At $2 for a new gasket i decided to order one and replace it. When taking off the induction flange i was very surprised at just how little gasket was left! Like 70% was missing/gone! Upon replacement with a new one my idle was too low and the idle screw needed to be increased. I’m really surprised that more green splatter was not showing considering most of the flange did not have a seal. As well as the rest of the cylinders are showing even on the jpi monitor, I’m temped to replace all the gaskets since they are not that expensive and wondering how many other cyl have part of their gasket missing. Here is a pic of what little gasket was left of the original one.