Help diagnose high EGT & high CHT

[skydvrboy]

I have one cylinder (#2) that is giving me high CHT's and EGT's when operating LOP.  This started the first flight after annual inspection and has progressively become worse.  Before when I would lean, all cylinders would peak in the following order 4-3-1-2 and the CHT's would drop to around 310-310-285-335 respectively.  During climb, ROP, the CHT's were around 390-350-320-375 respectively.  Other parameters: RPM 2500; MAP 24"; FF 8.0 GPM

After, when I go LOP the CHT's still peak in the same order, but cylinder #2 seems to stay at it's climb temperature.  For the first flight, climb CHT's were 385-355-320-370 respectively.  However once LOP, the CHT's were around 310-320-280-355. Other parameters: RPM 2500; MAP 25.5"; FF 8.7 GPM

On later flights it has progressively become worse, though admittedly the ambient OAT has climbed as well.  On one of my later flights I climbed to 9500' in search of cooler air (to no avail) and the LOP CHT's were around 340-360-310-390.   Other parameters: RPM 2500; MAP 21.5"; FF 8.0 GPM. 

When LOP Cylinder #2 always seems to be about 40 degrees warmer than the others.  Meanwhile EGT's on #2 are peaking around 1500 and I have always run about 5-10 degrees LOP after the last cylinder peaks.  Of note, on one low altitude flight, I set RPM at 2400 and MAP at 24" and #2 EGT peaked at 1550.  That is the only flight where that happened.

Now for my amateur incoherent ramblings... It seems that #2 is getting too much air and fuel and is peaking later and later.  In order to get the #2 CHT's to start dropping I have to lean so much that the engine is running rough.  This was never the case before.  In flight (and ground) mag checks show no issues, so I don't think it's a fouled plug.  I would think a partially clogged injector would cause that cylinder to get less fuel and run hot when ROP and peak sooner, which is the opposite of what I have going on.  Could an intake leak cause one cylinder to get too much air?  Is the exhaust valve sticking?  Any advice or other things I need to check out would be greatly appreciated. 

 

[47U]

2 hours ago, skydvrboy said:

I have one cylinder (#2) that is giving me high CHT's and EGT's when operating LOP.  This started the first flight after annual inspection and has progressively become worse.

What engine work did the shop do during the annual inspection?  What, if anything, changed?

[skydvrboy]

Not really any engine work done.  They fixed a cracked spark plug thread on cylinder #3; compression test; changed the oil and filter and cleaned the oil screen; cleaned the fuel screen; cleaned and gapped the spark plugs.  Basic stuff done at every annual.  Could have allowed some contamination to enter fuel, oil, or engine, but just as likely the timing could be completely coincidence.

[gabez]

reach out to savvy, don't do guess work. I learned my lesson 

[Oscar Avalle]

On 6/30/2025 at 11:55 AM, gabez said:

reach out to savvy, don't do guess work. I learned my lesson 

Agree share your data with Savvy they are great. Dont guess...

[PT20J]

Intake leaks cause noticeable roughness at idle and low power when the throttle plate is restricting airflow through the servo. Leaks don’t increase airflow much, if any, at WOT. 

If the engine is running smoothly it’s not a sticking valve. 

You can eliminate the injector nozzles by cleaning them. 

Since this happened after maintenance, I’d ask the shop what they did that might have caused this. But this only provides useful information if done soon after it leaves the shop. Memories fade. 

I always like to verify the instrumentation is accurate when I get an anomalous indication, especially if the engine is otherwise operating normally. I would swap CHT and EGT probes between cylinders 2 and 4 and see if the high temps stay with cylinder 2 or follow the probes. 

I might also check the condition of the probes and connections.