My rebuilt engine has 2,800 miles on it. The champion copper plugs are a light brown on the prongs, and the electrode is white.

They have a deposit on them as well. Just like my engine before I rebuilt it. What gives?

I might add that it loses power sporadically under acceleration, just like before the rebuild.

New 703 injectors, fuel pressure regulator, o2 sensor is a Bosch, new quality wires as well. Doesn't run hot. It will hunt for an idle between 5 an 700 sometimes.

 

Maybe help by diagnosing the spark plug condition first.

 

I saw that chart and its definitely fits the deposit picture. I can't upload pics via the cf app because it crashes.

Auto store guy said the spark plugs are running too hot.

 

Just saw a guide that showed it being a ash deposit and that it causes hesitation under acceleration. Which is what I have.

 

Did you rebuild it, or have someone rebuild it?

 

A shop rebuilt it.

 

As a point of data, I'd run a compression test on all cylinders. Gotta start somewhere. The compression spec for the 4.0 is 120-150 with no more than a 30 psi variation.

 

Certainly will tomorrow morning, but spark plugs 3,4,5 looked the same. Only 2,800 miles one this complete rebuild.

 

What caused the rebuild was the failure of piston #5. Had a quarter sized chunk missing from the side.

I believe clogged injectors led to the failure.

 

Did they also rebuild the head when they did the motor?

 

What champion plug # are they, and where are you buying your gas?

 

Yeah. Perhaps wrong plugs?

 

Again, it was a complete rebuild lol. And I have the right plugs,rcy9 something something. The champion copper plugs. From a new station called wawa.

 

9s huh?

http://www.summitracing.com/parts/cp...model/cherokee

 

Sum*****, let me pull one and look again.

Perhaps one little, very important, detail got looked over while doing the rebuild. Lol