Problem with High EGT readings

Hey all,
I've just begun to have 1450+ EGT readings on all cylinders, while the CHT's remain below 390 degrees. No attempt to richen things up (carb heat for example) improves things. I took off the cowl and see no exterior signs of trouble, removed spark plugs and they are nice and tan and even wet from running too rich. I tried a brief flight and all was normal, then on the next long leg they did it again. I recycled the Grand Rapids EIS and then only one cylinder persisted in giving me this reading. Am I right to assume it is an indicator/gauge issue or am I missing something more ominous?
Thanks in advance for your ideas.
Ron
RV-4 N8ZD

Have you calibrated your probes?

Hey, same problem (or is it a problem?). My EGT's have always peaked at around 1460, but after a recent change of plugs they are now peaking over 1500. All other indications of engine health are just fine. I also have an EIS 4000, new O-360-A1A with carb & conventional mags. I haven't been too concerned as I have read in numerous places that the absolute value of EGT readings are pretty inconsequential. It's only differences between cylinders or differences from what is "normal" for your engine that should be worriesome. I have always assumed that perhaps I just installed the probes a little closer to the cylinders than I could have (should have?). Anyway, I'll be very interested in any replies from folks more knowledgeable than myself. And if one was interested in calibrating the probes, how would you accomplish this?

Maybe it IS a guage issue..

Since all probes are suddenly moving in one direction, assuming they worked before, I would suspect the ground (common reference) path. I should know better than just that and haven't wired MINE yet but.. while you have one signal line per cyl to the sensor, you only have ONE ground line shared by all of the sensors (and hopefully not by many other things). A change in the ground impedence (resistance due to a bad ground lug etc) will affect ALL things referenced to that ground..

If it were mine, I wouldn't worry as much about the individual probes (since the problem is not confined to one probe) but to the common system (ground). Wiggle all of those ground lugs and make sure that they are tight and clean with no voltage drop (even millivolts) between where the probe is physically located and where the 'ground' input on the display device is.. cuz thats what it is measuring.

BTW. Make sure that the probe grounds are not going back to the EIS being shared with anything else. Got those 100W halogen landing lights plugged into the same ground bus?? Millivolt sensors and big-amp loads don't mix...

Keep us posted, help as able.
John

Ignition timing shift, advanced, could cause the egt to be higher on all cylinders. Although it sounds like you system is reading wrong, maybe checking the engine?s ignition timing is in order.
Good Luck,
Mahlon
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