Rough running / high EGT

Drew,

You said you checked the plug wires and caps, but did you check the #2 cylinder spark plugs themselves?  A problem with a plug is a long shot but also easy to rule out. 

Eric,

This is obviously a different set of circumstances since you have a carbureted engine. With the fuel lines and carburetors having been serviced as part of the 5-year rubber project, I would be suspect of a fuel flow restriction in the left carb. You can get a little debris from inside the new fuel hose that rinses into the carb float bowl, which will cause problems. It could also be other problems with the carb that only shows up when fuel demand is high. I would have Lockwood take another look at that carburetor. You should also check for vacuum leaks around the carb flanges and the crossover tube since both of those areas were worked on during the 5-year rubber change.  

Thanks Jeff.  This issue first started after installing new spark plugs. First step was to put original plugs back in to try to see if plugs were the cause. 

Since my previous post, I decided to focus on the spark plug connectors. When I changed the plugs I tugged on the connectors with my fingers. (Did not have recommended pliers then). I’m thinking I may have stressed the connection of the wire in the connector. 

I started with the top plug in #2. Removed wire from connector. Cut about 3/16” off the wire end and installed back on connector. On test flight that seemed to do the trick. No temperature rise. However on 2 subsequent flights, temperature temporarily rose when I pulled power back after reaching intended altitude after climb out. (Previously temp would rise on climb out as well). I could get temp to fall with either adding full throttle or further reducing power. Either way temp normalized after briefly rising and stayed normal at any power setting. 

Next step is do same on lower spark plug. Since this will require removing cowling, which is a pain, I will perform this at next oil change in 8 hrs run time. Will keep you posted. Thanks again for suggestions. 

I would like to offer what I think might be closure on this issue. After eliminating the above suggested possible causes, the issue persisted. However, I noticed that it occurred primarily when I reduced my power setting after reaching my targeted altitude. I started questioning whether it may be related to fuel pressure instead of electrical or sensor. 

Since my engine is on a new built with 135 hrs, I thought the fuel filter may be affecting fuel flow/pressure. I do have in line filters on each tank - before the fuel pump - that were checked at 100 hr inspection. I decided to change the Rotax filter aft the fuel pump.  On my last two flights, I did not see a rise in EGT temperatures. I’m cautiously optimistic. 

I’m asking the group if this sounds like a logical cause/effect. Or if anyone else has experienced similar. 

Thanks to all contributors.   

Drew