Pontiac GP GTP Car turns over but wont stay on


Asked by Jul 29, 2013 at 12:15 AM about the 2002 Pontiac Grand Prix GTP

Question type: Maintenance & Repair

I have had this problem before and the Mechanic told me it was a Position sensor.
Then I took it for an oil change and came out and it was running ruff (turn the car on
then it would fire you’d have to keep foot on the gas), it turned out the oil place bumped
a vac line, But I took it to another Mechanic to get it checked out just in case. They
told me to change the Fuel pump, Down pipe O2 sensor, Spark plugs, Wires, and
thermostat, which I did. Now I am going on a trip so I was having the tires rotated and
ac fixed and they told me it started running bad there, and it was going to be 1200 to
fix the ECM/PCM.  I said “Nope.” and brought the car home.  It has ran fine the last 2
days. Then I go to start it up and it starts but doesn’t stay on or once I gas it, it will idle
low for a couple of seconds and die. I smell gas. Has a full tank.  So here is my
question: Do I change the ICM (Ignition control) OR the PCM (Powertrain) The
difference of the two is 20.00 As well as the PCM/ECM you have to have it flashed.  I
have been told by another mechanic that the PCMs rarely go bad.  We have tried about
everything “little.”  Thanks everyone for your help.

15 Answers

I'd suspect a bad ignition switch here~

1 out of 1 people think this is helpful.

there is always a need to wirebrush the 1/0 cable lug as it attaches to the chassis/ground...must pull 300 amps or more comfortably~ ECM's do not like "brown power"~

2 out of 2 people think this is helpful.

So the Ignition switch will cause problems with staying lit not the ICM? Sorry, I am just trying to understand how that would be the problem. Does it have a sensor that tells the fuel pump something? Sorry for “stupid” questions. Thank you!!

1 out of 1 people think this is helpful.

What kind of plugs do you have in there? They should be iridium. Try a set of Delco wires. Had a similar problem with an '02 Impala police car. Changed the plugs and wires and it went away. BTW you should be running premium gasoline as well. HTH. -Jim

2 out of 2 people think this is helpful.

the problems you are experiencing are consistent with an ignition switch...yes it is only a guess, but you could check the 12 volts when in the on position to see if the switch is providing full voltage~

2 out of 2 people think this is helpful.
Best Answer

the "on" position will engage the fuel pump...if this does not happen, the switch is bad or the fuel pump is bad~

1 out of 1 people think this is helpful.

Judge- I do hear the fuel pump when I turn the key to on. Jim- yep on the iridium plugs. As well as I do run the premium gas though we are above 7000 feet and was told I didn't have to.

2 out of 2 people think this is helpful.

power to the coil(S) or coil packs should be 12 volts with the ignition on~ if not the ignition switch will be at fault~

1 out of 1 people think this is helpful.

hate to make you do this, but you must restore system ground...this means breakin' out the coarse wirebrush and un-doing the other end of the black cable (the one that attaches to the frame/ground) wirebrush the fat 1/0 battery cable lug clean and the place where it bolts to...what most people do not know is the amperage required to start the motor "welds" the lug and makes the power "Brown power" which causes failures at the ECU...so keep your car's brain happy and provide good ground to the chassis (where the ECU and ignition get their ground)~

3 out of 3 people think this is helpful.

a clean electrical ground will make ECU problems vanish...as if by magic!~

1 out of 1 people think this is helpful.

That's very good on the plugs and fuel. When it acts up does your check engine or service engine soon light come on (mine never did on the Impala)? Have you tried removing and cleaning the IAC (Idle Air Control valve)? It may be sticking sometimes. If you do get a check engine or service engine soon light have the computer (PCM) scanned and post the trouble code(s). That will help. Advance and Autozone auto parts stores will do it for free. HTH. -Jim

1 out of 1 people think this is helpful.

My money is on the fuel pump high speed resistor, under your front passenger fender, a real mother to get to. Easy enough fix though. I think theyre like sixty bucks or so. will let the car start, idle a couple seconds, then die.

1 out of 1 people think this is helpful.

I found out today a guy at work has been having the same problem with his '04 Impala. He said it's been going on about a month. His check engine light finally came on and he got a code for the mass airflow sensor. He is going to replace it today. I'll let you know if it solves his starting/ running problem. -Jim

I have this same problem and changed the mass airflow sensor. It ran fine that day. That night it started acting up again. It was like it wasnt getting fuel or the battery was bad possibly. Battery proved to be bad- and the gas tank was full. Changed the battery it started running great then went back to sputtering and not wanting to stay on


So far the guy at work has had no further problems since changing the mass airflow sensor. Hope your issue was solved as well. -Jim

1 out of 1 people think this is helpful.

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