OK Hello everyone, for everyone who DIDNT read my new member post, Im a very well skilled and trained mechanic, but This issue is driving me absolutly insane and Im looking for any suggestions and help from the rest of you "monte know-it-alls" out there. I have a 97 Monte with a 3.1L and about 124k miles. I gave the car to my gf who drives the car daily, she can drive 40-50 miles back and forth to work no problem, but if she stops at multiple stores(car sits for 30-45min while she shops) and trys to start it up again it starts, the idle sputters and surges up and down from 500-1800rpms for a few seconds than shuts off. when trying to restart it will just crank and crank away till the battery dies without turning over. Now for the fun part,
I changed the intake gaskets, head gasket, spark plugs and wires, coolant flush, oil change and the thermostat 4 months ago, since then I have changed the
-alternator (went bad),
-cam and crank sensor (for this problem),
-ignition module (for this problem),
-battery(was 5 years old/for this problem), none of this solved the sputtering/stalling issue. when the vehicle doesnt want to start, I have spark and fuel pressure, and it doesnt set ANY codes, Ive repaired and replaced multiple vacuum hoses that were cracked/dry rotted. if the car sits for about 30 min, it starts up and drives fine like there was never anything wrong...
Now Im hoping SOMEONE can help with with some possible options,
-I have a fuel filter I was going to replace it but didnt since I had fuel pressure, so that also rules out the fuel pump(dont know exact psi didnt put a gauge on it, but it was spraying out pretty strong)
-Tried the old "tap test" on the ECU.. didnt work. Was going to get a junk ECU and try that.. Other than that Im running out of viable causes and tired of wasting money on parts, and my gf is tired of getting stuck when it happens, it died one time when she came to a stop at a stop sign. I cant keep having her drive this around in this condition... someone here HAS to know what to do for this!! (besides a gal of gas and a match)

 

Ok so it got stuck again.. i sprayed it with some ether and it started up and kept running for a min or 2 before it started bucking again.. so i got it home and changed the fuel filter.. didnt help.. still sputtering.. not turning off this time tho.. but feels like a dead miss but no codes.. and the diagnosing continues...

 

When you changed the icm, did you have the old one tested? Most (if not all parts stores) can test it.
Do you have a code reader that can access the misfire data? It may not throw a code but it still may have some misfires (just not enough to trip a code).

It's tough to diagnose with out seeing it in person, but based on what you have mentioned you changed, I'm wondering if you have issues with fuel injectors or injector wires.

Passlock won't cause it to stall (the car just would not start) and maf failures on the 3100/3400 are not very common.

It's late and I've had a long weekend so I might be missing something. I'll try to reread everything sometime tomorrow.

 

Thanks for your imput!! I do still have the old icm, I didnt have it tested. I was thinking possible fuel injector problems with either the 'ECM controling them' portion or harness problems, or possible failing fuel pressure regulator. Im borrowing a pressure tester and the ECM programmer from work today and Ill check those problems later this evening. The ECM computer we have at work does EVERYTHING from flashing to changing the dwell on the fuel injectors... so ill use it to make sure all the injectors are firing correctly. And ill be sure to update on my findings!

 

Could be the MAF!!

 

OK so i hooked up a pressure gauge, connected the tech2 to the car and started it from cold temp and rev'd it and let it idle until it started stumbling. there was a history of misfires across all 6 cyl but nothing present, i did a cylinder power balance test, fuel injector pressure drop test, compression tested the cylinders... and all tested normal, until after about an hour when it started running rough, it started sporatic misfire on cyl 6. after a few min was misfiring on cyl 6 AND cyl 4. after about 10 min it was misfiring on cylinders 6,4, AND 2 (the front 3 cylinders) cyld 6 was misfiring the most cyl 4 the second and 2 was the least. I started thinking maybe the injector wiring, or maybe theres a blockage in the fuel rail line that connects the rear 3 and front 3 cylinders. after looking up on alldata for specs on the fuel rail, I realized that the 23-25psi fuel pressure was NOWHERE NEAR the 45psi I should be getting... SOOO needless to say I am changing the regulator in the next day or 2 and that "should" fix my problem. I'll update when I know more. Thanks for replying 'The Manic' and 'nitehawkjcb' I was looking for help and you were the only two who stepped up to help out. Thank You, I'll be sure to remember this if either of you ever need some help.

 

You're welcome, help is what many of us are here to do (or at least give ideas).

Honestly, i feel that narrows you to the fuel pressure regulator or fuel pump. Off hand I don't know a solid test to prove which it is. If you pull the vac line off the fpr and it has fuel in it, then you can be 100% sure it's the fpr.
I would still change the fpr first since it is far cheaper and easier then the pump. But if the symptoms continue I would look at the pump next.

 

Glad to help. But yeah that fuel pressure is definitely too low and could very well be the issue. I've been around these cars for a long time, and just threw out a possibility, but it sounds like you're on the right track. If you bump into any other hiccups let us know, that's what we're here for.