Low EGT at Low Power

Jeff Vaughan · #1 10-10-2011, 02:40 PM

I sure could use some help trying to figure out my engine issue.

I have installed on my TMX-0360 a LSE Plasma II+ on
my right and a mag on the left.

I currently have 211 hours with this set up. Note all four cylinders were replaced 93 hours ago. ECI recall) Recently at mag check I noticed a drop of 60 rpm when it has only dropped 20 RPM every time prior. The engine seemed to be smooth during this run up. As I taxied to take off I noticed that the egt temp on my # 3 cylinder was much lower than the other three cylinders 1,2,4 were 950 #3 550. When I applied power to check the mags again all EGT temps were about the same.

I checked the compression and it is fine.

I changed the plug, no difference. Put a new plug in and no difference.

Made sure wires are all snugged

I then restarted did the mag check with same non normal results. I did circle around the airport at 60%. CHTs were normal and EGTs were normal. Came in and landed and I noticed on roll out with throttle pulled all the way back the #3 EGT had fallen much lower in reference to the others. The engine was running rough as I taxied back on low power.

Got any ideas?

PROBLEM SOLVED SEE POST #15

DanBaier · #2 10-10-2011, 03:53 PM

Timing
Spark plug lead
Valve lifter (dry tappet clearance)

Jeff Vaughan · #3 10-10-2011, 05:08 PM

I will swap the leads and see what I get.

Timing - would I not have issues on other cylinders as well if it were not correct ?

Thanks

tkatc · #4 10-10-2011, 05:58 PM

Perhaps swap out the sensor?

Jeff Vaughan · #5 10-10-2011, 06:50 PM

Sensor swapped - no change

Klaus at Lightspeed has suggested swaping the 3 and 4 plug wire as they get their spark from the same coil. If the problem moves to cylinder #4 I need to replace the coil.

tkatc · #6 10-10-2011, 07:01 PM

That sort of makes sense to me...but what exactly is giving the cooler cylinder ANY heat if the coil is bad?

Jeff Vaughan · #7 10-10-2011, 07:56 PM

The mag plug !!

tkatc · #8 10-11-2011, 06:01 AM

Ahhh...i get it now. I say ditch em both and get dual p-mags!

Jeff Vaughan · #9 10-11-2011, 06:50 PM

Changed wires at coil - no change
Swapped out plug wires - no change

Believe Lightspeed is fine- it must have a bigger noticable change in RPM drop than the mag so now I suspect some thing wrong at the cylinder.

Rought idle low RPM does not smooth out over time. Lagging EGT and CHT at start up and low RPM

RV10inOz · #10 10-11-2011, 07:42 PM

Just a horrid thought

Low EGT without say a really high CHT which would indicate preignition, and that would be bad.

But given you have a normal CHT, or seems normal, it is entirely possible there is a lack of fuel and air getting to that cylinder, just like running an injected engine lean of peak and the injector clogs a bit, you et a further drop in EGT and a slight drop in CHT also (but may not notice).

You also get some rough running at low power.....like a cylinder not firing properly.

Now, just food for thought when you run out of things to look at. Cylinder head inspection for broken valve springs? Check the lift you are getting? Failed lifter or cam lobe perhaps?

I hope it is just a dodgy plug, but you could do well with thinking of whats next in the "look see" department.