rwabdu Posted July 10, 2022 Report Share Posted July 10, 2022 (edited) Any advice on if I should investigate this more? 1968 M20C, I notice EGT on #1 seems is always the warmest, I would expect it to be #3. I recently had an annual in April, compressions were good on all. Also replaced all manifold intake seals as I was having some manifold intake leaks last winter which evened things out for me and replaced the CHT probe on #1 because it went bad. Working on figuring out how to download my JPI info on a mac to see if I can pinpoint when this started. The increased EGT on #1 is keeping my fuel flow to about 10gal/hr at low levels and makes me wonder if the other 3 cylinders are being run too rich but maybe the difference is negligible. Edited July 10, 2022 by rwabdu Quote Link to comment Share on other sites More sharing options...
carusoam Posted July 10, 2022 Report Share Posted July 10, 2022 Odd EGT readings are always important to investigate…. Usual first step is to swap probes with a neighboring cylinder… If the problem moves with the probe… it is an easy fix. Since you fixed intake leaks recently…. It looks like one of the fixes didn’t hold…. Reinvestingate the intake on cylinder #1…. high EGTs can be a sign of exhaust leaking past the valve early…. Something that is best known earlier than later…. There are some nice pics of the engine monitor graphs with sticky valves…. There are nice pics of valves that have become sticky…. Start with the easy stuff first… See if you can download the data from the JPI… Up load the data to savvy…. click the share button… Post link here… Check the data to see when this EGT went awry… Do you have any engine data to go with this EGT reading? Is this at idle on the ground, or cruise MP/RPM at 10k’? Small intake leaks on the ground are easy to see in engine data at low power settings…. Small intake leaks at full power are nearly invisible at high power settings…. Best regards, -a- Quote Link to comment Share on other sites More sharing options...
Chessieretriever Posted July 10, 2022 Report Share Posted July 10, 2022 Try doing an in flight mag check and see if one of the two spark plugs on this cylinder is not firing. A bad plug will result in a higher EGT for that cylinder since the flame front travel is much larger causing a delayed peak pressure in that cylinder and subsequent higher energy in the gases exiting the cylinder when the exhaust valve opens. 2 Quote Link to comment Share on other sites More sharing options...
Shadrach Posted July 10, 2022 Report Share Posted July 10, 2022 Power setting? Phase of flight? Every summer I have to recalibrate my brain for the warmer CHTs that come with hotter OATs. Quote Link to comment Share on other sites More sharing options...
PT20J Posted July 10, 2022 Report Share Posted July 10, 2022 EGT is higher and CHT is lower than others. Could indicate lower power output. Agree that the first thing to check is ignition. Quote Link to comment Share on other sites More sharing options...
Shadrach Posted July 10, 2022 Report Share Posted July 10, 2022 I totally misread your post and focused on the CHT. Agree that ignition is the first place to look. Was the engine leaned when that image of the monitor was taken? Quote Link to comment Share on other sites More sharing options...
rwabdu Posted July 11, 2022 Author Report Share Posted July 11, 2022 Thanks a lot for your advice. I really didn’t think about an ignition issue. This was during cruise flight with a leaned out engine at 5000 feet or so. I’ll look around for a mechanic to help me pull the plugs and check them out. Much appreciated! 1 Quote Link to comment Share on other sites More sharing options...
Ragsf15e Posted July 11, 2022 Report Share Posted July 11, 2022 12 hours ago, rwabdu said: Thanks a lot for your advice. I really didn’t think about an ignition issue. This was during cruise flight with a leaned out engine at 5000 feet or so. I’ll look around for a mechanic to help me pull the plugs and check them out. Much appreciated! One thing you can do without a mechanic is a lean mag check (saavy.com) has instructions. If you have a bad/fouled plug, you’ll isolate it and be able to tell your mechanic exactly where it is. Cruise flight is a good place to check although you might be able to find it on a standard mag check. 1 Quote Link to comment Share on other sites More sharing options...
DXB Posted July 11, 2022 Report Share Posted July 11, 2022 13 hours ago, rwabdu said: Thanks a lot for your advice. I really didn’t think about an ignition issue. This was during cruise flight with a leaned out engine at 5000 feet or so. I’ll look around for a mechanic to help me pull the plugs and check them out. Much appreciated! As mentioned, an inflight mag check under the conditions where you see the high EGT is the way to go here. That will definitively narrow down which plug/harness/mag for #1 is the problem (the side of the ignition system where the engine runs rough and EGT plummets). Then the easiest way to start is to test / swap the relevant plug before going further. The plug most likely offender and it is cheap and is easy to swap. Bear in mind this issue can happen out of the blue when a plug fouls in flight. In the couple of instances where I have experienced it in 1000hrs of flying my Mooney, the issue cleared spontaneously before I landed and did not recur, so I did not pursue it further. 1 Quote Link to comment Share on other sites More sharing options...
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