I swapped in a new V8 into my 89 IROC Vert awhile after about 3 weeks of smooth running a fuel injector cracked and caused a small fire on the back end near the firewall. I replaced everything and repaired wiring etc. however the car hasn't run smooth since. Also I took it to the track and did 3 runs on the 3rd run the car started acting up not wanting to start unless the pedal was floored and kept stalling out. Also when you go WOT the car hesitates and almost stalls out. After the small 1 sec hesitation the car booms and takes off as normal.

I've checked for spark thats good. Just did timing 3-4 weeks ago so that shouldn't be off so I'm not sure where to even begin to figure out whats up.


FYI: The solenoid attached to the distrubutor (EGR Solenoid) was destroyed in the fire and lack of another we just didn't use it and rerouted the vac lines could this cause that wierd problem with the smoothness?

 

If your EGR valve is open even a little at idle it will cause a rough idle. Your hard start and hesitation could be caused by TPS, MAF, or ignition system. I would lean towards the TPS based on your description. In your inspection of wiring after the fire did you carefully inspect the wiring inside the main loom. Perform the TPS voltage test sequence. This will point out any faults.

First, test for voltage between pins A & B( blk wire and blu wire of the TPS connector with key on. Should be .5v at idle and smoothly increase as throttle is openned to 4.5 at WOT. Is voltage as specified?

A scanner is helpful at this point to determine whether the ECM is receiving correct sensor signal.

 

The distributor and everything around it was burnt up bad. We checked all the wires we could and replaced those that had to be replaced (mostly to the fuel injectors). I don't really want to guess out a vacuum issue either but were not hearing any suction etc.

The ICR solenoid is not hooked up since the solenoid got melted to a crisp as the burning fuel was shooting right onto it. With bypassing the ICR cause this? It just seems odd that the smoothness and someone lack of horsepower was just the only problem till all of a sudden now were getting this issue of stalling as if something was jarred loose.

 

ICR? I assume you mean EGR. Bypassing the EGR solenoid should not cause any significant issues. As long as the valve itself is in proper working order. The solenoid only prevents EGR function when engine is cold or at WOT. Unless the valve is openning too easily because of a broken spring or stuck open, the engine should run okay without the EGR solenoid.

Perform the TPS test as directed. Also, test the MAF or MAP, whichever your engine has. I know the switch came with the 90 model year but some late 89s were speed density. I will not go into detail on the tests for these sensors. You can find the test sequences by searching this forum.

Again, a scanner could save you alot of wasted time on this diagnosis. Being able to see ECM data and knowing how to interpret what you see is key in diagnosing these cars. A scanner capable of communicating with your vehicle can be had for as little as $300.