A few weeks ago I had a bad 5500 RPM stumble. I replaced the coil and it was completely gone.

It has now returned so I really dont think its the coil. It does not show the dead opti symptoms like the 3K RPM stumble. Power all the way up to 5.5K RPM is very strong.

I have a like new set of MSD wires, fairly new spark plugs and ICM.

What else can cause this problem?

 

My whole ignition is new from the Opti, ICM, coil, and plugs. The only thing old is the wires. I had a high RPM stumble past 5K with the old components, and I still have it, though not as often and only when the engine has been running a while. I'm still trying to figure this crap out. Maybe when I finally switch over to a Delteq it'll go away.

 

Im thinking about getting a new summit brand optispark to try and eliminate my 4500-5000 rpm stumble, its like the car falls flat on its face at WOT! New wires, plugs and coil haven't fixed the problem. Very FRUSTRATING!

 

I am not convinced its the opti because power up to 5.5k is very strong. I think optis are supposed to crap out around 3K.

 

dime to a dollar says its knock retard pulling your timing out.

 

Nope, I have a scanmaster in the dash. My care has nearly no KR. I get just a tad when its not warmed up.

It seems to be intermittant as well.

 

How old are your plugs? Maybe you burnt a plug wire?

 

Plugs are 6 months old, they are NGK Iridiums gapped at .055.
I checked the wires and none are touching a header or show any evidence of wear or burning.

I am wondering about fuel pressure issues, I replace the filter a few years ago. I might just go ahead and do it again.

 

The fact that it completely went away after replacing a coil for weeks, then came back leads me to think its somthing around the coil.

I have been thinking that maybe its an engine grounding issue.

Obviously the grounding wire comes off to replace the coil. I am going to beef up the grounding strap and see what happens. A bad grond has intermittant written all over it.

Anyone want to agree with this?

 

If it does please let me know!

 

I think part of the problem was bad BP gas. I filled up with Shell and no stumble. I was also getting a lot of knock retard.

I also removed my leaner tune in favor of an older slightly richer tune. Still no stumble.

My O2's have gone from the 850's back to the 890's and all seems well. I also relocated the engine grounding strap.

So life is good again, I hope.