EGT/CHT discrepancy, valve or sensor?

[Pierce]

I’ve been trying to get out club’s plane out of annual for a month now. We keep having performance issues and sent the carbs off to be rebuilt and that seemed to help a lot. 

Now I’m seeing a big difference in EGT on the ground and a small difference in CHT. 

EGT 1 is running 1046 vs EGT 2 at 540 while idling on the ground. 

CHT 1 is 187 vs CHT 2 at 206. 

Anyone think this might just be a probe issue? I’m now worried about a valve sticking or burning out on the 1 side. 

Thanks for your thoughts. 

[Pierce]

[GlennM]

Looks like you might have a bad TC (secondary junction) or a bad connection to the EMS.

I don't recall my idle CHTs, i usually get about 7°-8° difference in flight.  19° differential could be conceivable with low airflow in the cowling.  The cooler CHT and hotter CHT are the same as mine.   I run a carbureted 912ULS in a CTsw, though.

[Tom Baker]

How is it running? Smooth at 2000 RPM? The CHT split is nothing to worry about. When you put gauges on it to balance the carbs what do they show? Are they balanced? You could use an infrared temp gauge to check the temps of the exhaust stacks compared to the EGT. EGT probes are fairly inexpensive, ($36), so you could replace the one that is reading low.

In my experience a stuck valve will run real rough, and no compression on one cylinder. A burnt valve will also give low compression. What are the compression numbers?

[Pierce]

Thanks for the input. Plane is running well now that the carbs have been overhauled. Less than 150 drop on mag check and within 20 of each other on the run up check. 

I'll work on getting the sensor or connection replaced. 

I'm not sure about compression checks. I need to get those from my mechanic. 

Thanks for the help.