Dan Reagan wrote:

 

About 10 flight hours ago my #4 EGT dicided to start running about 150 degrees less than the others.  This is a FADEC engine so there is a possibility of injector problems but other than that please give me some ideas what has changed.  The temp shows approximate correct ambient temp when shut down overnight.

 

Dan,

 

Try to isolate whether this is a cylinder problem or a probe/connector problem by trading sensors and connections between cylinders if possible. If you have enough lead wire, switch EGT probes between #4 and another cylinder. Leave the probes connected to their original wires going to you monitor. Test run the engine. If #4  on your monitor still indicates 150 degrees low, you have a defective sensor or wiring. If the cold cylinder now shows to be the one that you swapped above, you have a problem with #4 cylinder.

 

The more likely event is a defective probe or wiring.  You can further isolate this by changing the probe connections so the #4 cylinder is again hooked to the wiring for #4 in your monitoring system.  Use the same logic as above to decide whether you have a defective probe or bad wiring.

 

Hope this helps.

Bob P