'94 Chevy Lumina Euro 3.1L T vin code, Engine erratic

[Tkaynk]

I have a 94 Lumina Euro, 3.1L T vin code....car ran great then just died, no warning, no noise, no hesitation, just died, would turn over but not start. Have replaced spark plugs, wires, fuel filter(was bad dirty), car started and ran rough for about a minute then ran smooth...I drove it to the store, post office and back home, parked it, wouldn't start, would crank, but not start. Had it towed back to shop I work at, the guys changed the ignition module(after changing not firing coil and still having same prob), coils(one was not firing), fuel pump(only had 35 lbs of pressure) still will crank, not start most of time, every now and then it will run, but roughly like it has a miss. Compression was checked and is good. Fuel Pressure is 45 lbs at the check valve. Spark is good. All of us are scratching our heads. Checked for vaccuum leaks, nothing found. Hooked up Diagnostic scanner, no codes present, no misfires detected, says everything checks good. No engine light ever came on, even tried to jump it with a code key, only flashes code 12. We have narrowed to the fuel system, only because when it does start, it runs rough, but if you spray fuel into the throttle body it smooths right out. They even change the fuel in the tank, thinking maybe it had bad gas. These guys are BIG truck mechanics and rarely work on cars, so they are trying to help me, but aren't sure where to go now. I was thinking maybe the fuel pressure regulator? Does the upper plenum have to be removed to get to it? Can it be checked? Or maybe the CAT is plugged? Never had a plugged one so just guessing on that one. Please help, thanks.

[maxwedge]

Welcome to AF,you can elimimate the cat by disconnecting the engine pipe or doing a back press test at the o2 port, but this is not the issue based on your symptoms. Some or all the injectors could be clogged, check for any blown fuse fuses for the injectors also. You say dirty filter so there is a hint also.

[Tkaynk]

OK thanks, I have the plenum off now, and will check the injectors, also the regulator, which may get replaced just because it's visible now.

Are there any other sugesstions?

[Tkaynk]

Update: Changed fuel pressure regulator, and vacuum connector which had a hole in it. Now car will idle, will idle all day, but as soon as the accelerator is touched the car stutters and dies. I am completely out of ideas. HELP?

[maxwedge]

Sounds like fuel delivery to me check the fuel pressure as this happens, you need 37 psi.

[Tkaynk]

Car has steady 45lbs of fuel pressure, specs call for 41-47. Also crank position sensor was changed today, no difference. Will idle fine, touch the gas and it dies. Any ideas?

[richtazz]

IF the injectors check out ok (the resistance is around 11-12 ohms and within a few percentage points of one another), check the TPS with an ohm meter for a flat spot or dead short, and check the MAP sensor vacuum hose (it runs under the upper plenum) for splits/cracks. You can also try a "tap test" on the MAP sensor. If tapping on it lightly with a screwdriver handle causes the idle to change, the MAP is bad.

[Tkaynk]

Thanks I will check the TPS and injectors, already changed the MAP, and checked all the vaccuum hoses. And I've tapped everything in sight, lol.