Rough running / high EGT

You could start with swapping the probe to another cylinder to see if the problem follows the probe.  I have seen the 912iS probes read erroneously hot when they are beginning to fail.  Also, what RPM do you get at WOT during takeoff? The 912iS will run hotter exhaust temps if engine (prop) is lightly loaded. If this is a factor, you would likely see fairly cool CHTs at the time EGTs are high.  In addition to the typical thinking that EGT is dependent on mixture, also remember that CHT = power used for thrust, and EGT = power wasted out the exhaust. Loading the engine will typically lower EGT and raise CHT, and the reverse is also true.  

Hi Drew

There is simply not enough information to make a guess as to any reasonable answers.  The engines are run for about an hour at the end of assembly by the factory so if this is a new installation everything is suspect.  If this is an old installation what type of aircraft, prop and what RPM.  What fuel.  

Some details might help get you some things to try.

 Cheers

Thanks Jeff.

WOT on climb out is 5,100 rpm.  I will swap out prob to see it symptom follows the prob. 

I’m curious why I get the rough engine, and if faulty prob would be a cause.  

Drew

Thanks. The installation is 912iS in a Sling2 with a 3 blade Whirlwind prop. 125 hrs time on engine. I have only used Unleaded Ethanol Free MoGas.  The first 100 hours were flawless. Symptoms just started after 100 hr inspection. 

Hi Drew

I missed the part about the rough running engine prior to the EGT rise.  It’s my understanding that the EGT data stream does not affect the ECU program.  The Manual seems to indicate that it does, but knowledgable folks here on this site insist that the program does not use the EGT data at this time, though it may in some future firmware update.  Let’s see what RW has to say about that. 

A simple ignition problem can cause high EGT in the affected cylinder.  For instance, if one of the two spark plugs stops firing this causes the fuel burn to be slightly slower and more heat energy is wasted out the exhaust system.  This would also give you the rough engine.  Since this started after maintenance I would check the spark plug wires and spark plugs in that cylinder.  It could be a simple as putting two much heat transfer paste on the spark plug threads causing the plug to misfire.  Also check that the spark plug caps are screwed tight onto the wires and snapped tightly to the plugs.

If nothing is found, I would swap the probe to rule that out.  Be careful doing so, if you drop the probe or hit it against something on accident the ceramic element inside the cage on the inserted end can easily break.