Some strange happenings with CHT and EGT

John, I don't know the answer off the top of my head. What are the rpm indications when the anomaly occurs? Is this a 912UL, ULS or 914?

Do you have an ammeter, if so, is the amperage dropping significantly?  How many hours on the engine? When it goes into the red, is it immediate with a throttle reduction? When you say you swapped sensors, put in new ones or exchanged locations? Are you measuring all 4  cylinders or just one per side of CHT's and EGTs? Once on the ground in taxi does it drop immediately as you noted with a throttle increase, or drift down into operating range? Any recent changes to engine, e.g. spark plugs? Air Filter, etc. Any power device turned off when you taxi after the spike? Not familiar with the Garmin, but if it includes a database have you taken a look at what it is telling you? Is the reading on an analog instrument or the EFIS?

Jack

Charles J. Norris wrote:

John, I don't know the answer off the top of my head. What are the rpm indications when the anomaly occurs? Is this a 912UL, ULS or 914?

Do you have an ammeter, if so, is the amperage dropping significantly?  How many hours on the engine? When it goes into the red, is it immediate with a throttle reduction? When you say you swapped sensors, put in new ones or exchanged locations? Are you measuring all 4  cylinders or just one per side of CHT's and EGTs? Once on the ground in taxi does it drop immediately as you noted with a throttle increase, or drift down into operating range? Any recent changes to engine, e.g. spark plugs? Air Filter, etc. Any power device turned off when you taxi after the spike? Not familiar with the Garmin, but if it includes a database have you taken a look at what it is telling you? Is the reading on an analog instrument or the EFIS?

Jack

Hi Charles,

This is a 912ULS. Running Garmin Glass - So all are info on the glass.

The problem is I don't know how quickly it gets into the red, but quick enough that I don't know until I get an EMS warning.

I swapped sensor locations, to see if the problem followed the sensor - but it did not.

Yesterday it dropped the second I applied throttle. (The EGT that is) 

Changes - yes had the 100, but it did it before and after the 100.

No Analogue.

Not sure if the Garmin logs it all.  Hmmmm.. Might look for that.

I've seen this with CHT's and EGT's before. Sounds like a poor ground. You have a ground just one that has become lose or deteriorated over time. Could even be a ground wire that the insulation has worn through. .  

Thanks Roger.

I have checked all the wiring and it all looks good.  It's such a pain!  :(

Wires may look good, but can have a poor connection from something being lose or corrosion you may not see. All wires and connections should be considered hand tight, but wrench lose. Put a screwdriver or wrench on all connections.

You have a ground, but maybe a poor one. This has happened to me many times and now it's the first thing I check.