A

av8orB

I'm New Here
I have a new (first run rebuilt) IO-360 B1B that runs well but at 290 hours, I started to see an odd behavior on the #1 EGT.

I have a 4-probe engine analyzer and CHT/EGT has always been well matched between the cylinders. By well-matched, I mean CHT is +/- 20 between cylinders and EGT at nearly all conditions but peak is +/- 50 between cylinders (peak could show +/- 75-80). I was quite happy!

Recently, however, the #1 is misbehaving.
Significantly Rich Of Peak (ROP) it runs at least 100F cooler than other EGTs (while the #2,3,4 stay well matched).
At Peak, it runs at least 75F EGT hotter than others.
Lean of Peak (LOP), it runs at least 150F hotter than others (up to 1550).
No observed differences in the CHTs from before.

First, I swapped probe cables. Then I swapped probes. Then I put in a new probe (into #1). Every time, the problem stayed with the cylinder so I believe this is not a probe/gauge problem.

My first thought was a bad exhaust valve but I don't see why that would lead to ROP cooler operation.

Any thoughts?

-Brian
 
Maybe

You may have a dirty or clogged injector on the #1 cylinder. They are east to get to. Just undo the small fuel line into the injector and take it out. Be careful that you do not lose the little insert.
I have had success cleaning them with MEK or something similar. You can also use a jewelry cleaner to vibrate them without doing damage.
Might be a place to start..
 
"My first thought was a bad exhaust valve but I don't see why that would lead to ROP cooler operation.

Any thoughts?

-Brian"

Brian:

Are all the spark plugs the same?
Are any plugs fouling?

How are the CHT's?

Check the bolts that hold the intake manifold & flange.
If they are loose you could have a little air leak and that would cause a lean condition.


Barry
 
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