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Pontiac Repair/stalling and drivability problems

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QUESTION: I have a 95 firebird with the 3.8 engine and auto trans. the car recently started stalling randomly while driving. just out of nowhere it will shut off. it will usually start right up and I can continue driving. it occasionally runs poorly as well almost like its misfiring or something or literally in a "limp home mode" where it feels like there's no power and it has trouble moving unless you really hit the gas.  I got a code of P1374 indicating the 3x portion of the CPS was failing so I replaced the CPS and STILL have the exact same problem and the code came back.  wiring to that sensor looks good, clean, tight etc.
any ideas on what the problem could be?  much appreciated for your time.

ANSWER: Hey Mark;

That is an odd code to set on that engine. did you replace the crank sensor with a genuine AC delco part or an aftermarket one? I have seen really odd things happen with aftermarket parts. I would double check all your pin contact at the crank sensor make sure you don't have any hogged out terminals same at the ignition control module which is under the coil packs. next make sure all the ground wires on the engine are clean and tight. ther are more then one. also the grounds between the batter and body and the body and the engine. there are some up on top of the strut towers on the engine block and possably on the accy brackets on the front of the engine make sure none of them are loose or corroded. if so repair and try again if it comes back again I would lean towards an ignition module. DO NOT buy aftermarket use only genuine GM parts from an AC delco dealer or from a dealership.  Good luck :-)


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QUESTION: thanks.  I checked the grounds.  the main ground from the side of the block to the battery looks good on both ends, the ground from the battery to the frame looks good (tight and on non painted metal). the alternator is solid as well for both grounding and +. there is a thin (1/4 inch) ground strap underneath the car that is ripped in the middle so its doing nothing, but I highly doubt that's the problem with that HUGE like 2gauge line bolted to the block and battery.
also, not sure if I made it clear but I got the P1374 code (3x signal) with the original factory CPS, then replaced it with a brand new one (duralast), cleared the code, and it came back within 20 miles or so.  then on Wednesday I cleared it again and it hasn't come back yet (40 miles now). the connection on the CPS looks great as does the wiring.
Very confused.

ANSWER: any missing ground is an issue. They put them on there for a reason.

In a nut shell the CPS has 2 sensor in it and sends the signal to the ignition module to control spark and fule is it doesn't see on of the signals or if it just doesn't see it correctly (due to an interanl fault in the module) it will set that code and the engine will be in non sequential injection thus the poor running.


---------- FOLLOW-UP ----------

QUESTION: as a test I replaced the ECM (main computer) which didnt help at all. as a next test I probed the wire from the ICM to the ECM that carries the x3 signal and the signal is SO weak that simply touching the exposed wire with my fingers causes the car to shudder and stall out! I cleared the code and repeated this test of touching the wire and boom - instant check engine light with the exact same code! I then did a continuity test between the ICM and ECM on this wire while jiggling everything around and the wire checks out fine.  so I'm 99% sure the problem is a bad ICM.  it was replaced about a year ago with a Delphi brand one.  you were saying AC delco exclusively for this car so in your opinion do you think the Delphi is junk and is probably the cause for my problems here?
thanks.

Answer
Yes the parts we get at the dealership are the same parts you can buy at the autoparts store if the carry genuine ac delco parts. if youching the wires induces this then I would suspect either a bad connection in the module or you have a hogged out terminal in one of the connectors. if you probed the terminals with the incorrect terminal size you justy decreased the amount of drag that terminal has on the pin in the ICM so I would look long and hard ta that before you chuck any more parts at this. you hay have mad the problem worse probing the wires. if you probed them from behind (back porbe) you could have bent a terminal too.
good luck :-)

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Todd Puccio

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General auto repair,electrical issues,driveability issues,anti-lock brakes,SIR systems,HVAC,engine performance,Gm specific. I have worked at my current dealership since the 1990 model year anything much older than that I have limited exposure to. I do not have very much transmission experience so those question you may want to ask of another expert. When you send me a question let me know the exact make/model/engine and year for the car or suv you have it makes it easier to answer the questions that way. If your happy with the answer I gave you please feel free to Donate. This is a free service to you and I am not compensated at all by this web site. I have 22 years of experience to share with you and my knowledge wasn't free to me. I had to pay for my education.

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Experience in the area: I have been a technician in GM dealerships for over 22 years and I am a ASE master technician. I work at a Buick and GMC truck store Previously I worked at a Pontiac GMC store for 18 years. I Served a a lead technician when dealership was on a team system. I just recently moved to a Buick,Hummer,Saab Store when my franchise was purchased by this dealership. Organizations: ASE master technician

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Education/Credentials:High school diploma,2 year vocational school degree 2 year college degree. Associates degree in applied sciences (auto technology)Awards and Honors: GMC master technician

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Master GMC truck technician Master ASE technician in 9 categories

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