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YJ - Timing Question/Exhaust Pop

509 views 3 replies 2 participants last post by  **DONOTDELETE** 
#1 ·
I don't have access to my YJ right this moment, so I can't do a trial & error diagnosis on it, but here's the deal.
While at idle (anywhere from 800 - 1100 RPM), I will randomly get a slight "pop" out of the exhaust pipe, not through the carburetor. It doesn't seem to be associated with any particular cylinder, hence the random nature of it.

Would this "poping" noise be indicative of the timing being too far advanced, or too far retarded?
 
#2 ·
Timng may or may not be an issue. Usually the timing would be affected at higher RPM's not the lower RPM. But to be sure do a compression and leak down test to qualify the cylinders and valves.

The engine could be running rich... and the unspent plasma hits the Converter or hot manifold and explodes.

A valve could be burned and plasma is escaping to explode in the exhaust.

The engine could be running lean and heating the exhaust system causing a late ignition.

There could be carbon in the engine heating up an causing late ignition.

Ther ecould be as vacuum leak cause heavens knows what...
 
#3 ·
Since you brought up the point that it could be running rich..I can contribute this:
The tailpipe gets a black soot around the outside of the pipe, so is it safe to assume that it's running rich if I consistently develop that soot ring around the end of the tailpipe?

And due to the nutter bypass, I have only a bare minimum of vacuum lines, all of which are not leaking.
 
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