I feel your pain my 93 "was" doing the same thing. I also belw out a couple seals after a hard run. Turns out I had 2 scored piston walls. Have you done a compression check yet? Do you have an oily film in you throttle body? I also found a corroded pin on the opti harness when I removed the motor so "maybe" that was part of it??? Good luck and keep us informed. I also had a pcmforless tune and the car ran 100% better but the skip can back a couple of weeks later. Alvin actualy rode in my car and did the custom tune from scratch for me but to my despair it didn't work . Oh well I will be getting a new tune from him for the new motor as soon as it is finished.

 

How was your cam put in? Was it degreed? Maybe a lifter sticking or a valve stock open. Thats one heck of a problem you have there... What about your fuel pump, even though the pressure is good, does the pump keep up with the car when your stomping it? It might be lagging a bit.. What about your harness, since your wires were burned maybe you have something else burned down there.. Maybe the knock sensor harness or the sensor itself. Does the timing change when your stumble occurs?? If so it might be your knock sensor.. How about the rocker arms, maybe they are too tight, I cant remember if you said it happened at idle or just at hard throttle..

 

Just at hard throttle. I haven't done a compression test, but here's my though process.

It's only when moving the throttle at a fast pace, and it's only momentary at that. When Joe (the mechanic who did my car) had my heads off, he said that the inside of the motor looked fine. Still had cross hatching on the cylinder walls. If it indeed was a mechanical problem, wouldn't it be a continual type of problem instead on only presenting itself on fast throttle movements???

Everything in the valvetrain is brand new, and I don't think it's anything there. The thing is, the car just ripped on the initial tune, and on the #2 and beyond chips, had the problem. Unfortunately, I don't have the first chip/tune to test again.

 

Yea, I would guess that if it was me(tune).... Are you sure its not your fuel pump???You said it was lean up top right?? It says it in your sig.. Maybe your fuel pump isnt holding up at high fuel demands..

 

I'm positive it's not the fuel pump. Pressure checked out A O-K.

 

 

My sentiments exactly. Tune??? I wonder.

 

It's not the tune. AT LEAST IN MY CASE, i DIDNOT CHANGE A THING IN THE COMPUTER AND THIS PROBLEM DEVELOPED.

Interesting fact.. I took my car through emissions (failed miserably yesterday twice) I thought I would cheat and unplug 6 injectors run it on 2 cylinders and fly right through. Well the car kept backfiring and it was high on HC which means unburnt fuel.

I think I may have either

A. cylinders misfiring/not firing

B. Leaky fuel injector that floods a cylinder every so often

 

Did you change the O2 sensors, and did it help??? I have yet to do mine, but when I swapped them they looked OK. I'm going to give the tune mod a shot if I can find the right parameter to work on.

 

Broke my clutch fork so this experminet has been put on hold for a day or two, bu i have a laptop to datalog on now. This problem is done as soon as I get the logs going on. Im gonna try messing with the accelerator pumps ettings in the computer and go fromt here.

 

Ok well got some datalogs and the only thing that is out of line is

A. MAP sensor feedback does not match my manual vacuum gauge. Intake leak?

B. Spark advance and retard is funky and does not match my predetermined settings from lt1 edit. Optispark almost failure?

 

I'm pulliong the direct port kit off tonight and plugging the holes, this will tell me if it is an unmetered air problem. I am leaning towards this because of the vacuum issues and the opti tested ok.

 

What was your map showing at idle out of curiousity, in volts????

 

MAP at idle in volts, I don't know, but in KPA it was aroud 60.

It is now fixed, it was intake air leaks. basically unmetered air getting into the manfiold. I would check intake manifold gaskets and throttle body gasket and make sure that egr system is functioning properly or blocked off corectly.

If you need more help with your prob, email me and I can try to help you over the phone.