Hi. I have a 1997 Pontiac Grand Prix that i bought last week. It ran great no CEL ON. Hot a coolant flush, oil change and my husband did a tune up cause it was showing signs of needing one. New plugs and wires, He could not get one plug out so he left it. Went to get emissions test and computer wasn't ready. Still no check engine light on. Drove for 5 or 6 days no problems. Went back 2 days ago to get emissions and passed yesterday morning. CEL flashing.
Came on, spit and sputter and cut off no power no lights no nothing. Car sat for a few minutes with battery cable off put back on, had power then tried to start no luck. Let it sit a little longer started fine no CEL. Drove multiple places no problems. Went somewhere late last night engine light started flashing. The car spit, sputter and then cut off. Did not start back up. Had to get pushed to the house. We know a flashing CEL is a misfire so we assumed it was the spark plugs not changed this morning.
Sprayed nut buster on plug and got it out. Replaced with brand new. Tried to start and no start. Engine light still on. We hear the fuel pump so we know that's fine. Help. I don't know what to do next. This is our only vehicle. We had the same thing on ours after we got a transmission rebuild and there are 3 sensors on the outside of the trans. You can see one when you move the air filter housing. That's what we were told was the reason for that.
Answer: Ok, there could be a few different things causing your issue. First of all, just because you can hear the fuel pump does not mean it's putting out enough pressure to start the car. I would highly recommend doing a fuel pressure check to see if it's within spec. You should have at least 45psi with the key on for your particular vehicle. If it's any lower than 40 you need a new fuel pump. Check the fuel filter as well, it can be heavily clogged and cause a low volume situation.
You may also want to check the fuel pressure regulator for any signs of leaks. If the rubber diaphragm inside it is ruptured, it will leak gas through the vacuum line into the intake. This would cause a rich condition (too much fuel) which can cause sputtering and hard starts. Another thing to do would be to re-check all your previous work. Maybe a spark plug got cracked upon installation, maybe a wire was left loose or improperly installed, maybe a spark plug had the gap closed by accident.
All possibilities.I would also highly recommend getting the car codes scanned to see what trouble codes are making the check engine light come on and/or flash. That will definitely help lead you in the right direction for diagnosis. From what you describe it surely sounds like something with the engine, whether it be electrical, fuel related, ignition related, or what have you.
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