Hello, I'm trying to help my step dad fix his 91 z28 (completley stock)

Original problem was car just died while driving, started back up and ran a few mins then died again. New fuel pump, filter, ignition module, AND fuel pressure regulator. Still won't run. It will Start once in a blue moon and barley idle, but touch the throttle and instantly dies.

Car has 47 psi at the fuel rail, spark at coil, spark at plugs and no trouble codes. Ether in the intake dosen't seem to help either. The shop put a new fuel pump in and it started, and ran fine. Sat two minutes and it never started good again. I also unplugged the ignition advance wire (tan with black tracer) and no help either. I have yet to pull the plugs but will try this week. My last guess is MAP sensor or a demon possesion.

Any ideas? I'll be checking TPS and MAP voltages this week.

 

Do you have a service engine light. Does the service light blink once when turn key on and then go out? If not you may have a ECM or prom failure and you may be in limp home mode. But it should at least run. I'm wondering if the injectors are even firing, may be a VATS failure but wouldn't think the starter would engage if that is so. Check that you have 12v at the injectors when cranking. Or use noid lights.

 

That would indicate a spark problem but are plugs wet or dry when you have no start?
That at least lets you narrow it down to spark or fuel problem

Should have 12V at injectors any time key is on, not just with cranking

 

I doubt it's the ECU/PCM because occasionaly it does start and idle very, very poorly.

I am gonna pull a few plugs and look em over. The service light is not on, and I checked for stored codes and there were none.

 

ive seen new ICMs be bad right out of the box.
Map sensor?
vacuum leaks?

 

ohm your injectors

 

Yes VetteOz is correct that there is 12v at the injectors with key on and they fire only when grounded by the ECM. I was thinking more of a 12 test light (or Noid light) where you would see it flash when cranking to also rule other things out . But remember the basic fuel and spark rules. Everyone has given you good advice that should help to narrow the problem down.

 

Did you check timing? I had a reman distributor, bearing was seizing and jerked the timing a few degrees out. I finally adjusted it to stay running then the bearing seized fully and the whole thing spun 90 degrees and it stopped running before my eyes.