98 Grand Am -- 1st probelm in 100k. Help me out guys [Archive] - GrandAmGT.com Forum


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02-09-2008, 06:00 AM
It's been so long since I've had to tinker with this car I've gotten a little rough on my abilities I guess.

98 Grand Am GT 3.1 106k. It's been maintained by the bible and never abused.

Just started "sputtering" this week.

Here's a quick breakdown and a copy from another forum I typed this on.

Wife calls today and says the car is sputtering upon acceleration. Only happens when the vehicle is up to operating temps.

I go get her on the parkway, check the car, she had shut it off. I look things over and just figure we'll limp it home. She drives off and it's driving fine. It had been turned off for about 20 minutes.

I get home, look @ it again, pick her brain.
Monday she got gas.
Before she got gas, when she attempted to increase speeds above 60mph it felt like it would not want to go. No sputtering, etc. She lets off the gas, rpm's jump up then back on the gas and the vehicle then accelerates normally.

After she got gas it has a "shutter" / shake at full operating temps with the engine under load. (mostly @ 55-60mph & from dead stops)

I push the brake, car in gear and get into the gas easily like a power brake deal. About 2000-3000 the car sputters/shakes almost like it has a bad miss.

I'm thinking it's either bad fuel or the fuel pump going bad? Fuel filter is changed every 10k and the old ones cut open for inspection. The last one I changed looked normal with no excessive sediment/filth.

My work truck did this on bad fuel then the fuel pump went shortly after.

I'm more than capable to do the work myself but hate to drop $300 on a fuel pump if that's not it. Any other suggestions?

No engine codes, idle is smooth as glass.
Only happens when engine is under load. It will rev up fine with no load.
Throttle body is clean, fuel filter has about 6k on it.
02 sensors have never been changed--still gets 30mpg...I doubt that would cause this.
Spark plugs/wires @ 65,500k on 12/2002.
I replaced a coil about 2 years ago for a small miss @ idle.

I'm going to pull the fuel filter and drain a bit of fuel to see if there's water in the gas...??

Other than that I'm assuming this is a trial & error guessing game.

Thanks for any help guys.

02-09-2008, 07:52 AM
Air filter or spark plugs/wires? Dirty injectors?

02-09-2008, 08:52 AM
Just changed the plugs/wires/fuel filter this morning.

fuel pressure is within specs @ 42psi on a key cycle, 42-45 when running, no bleed down on the pressure when engine is stopped.

02-09-2008, 07:24 PM
mine did that when the MAF was going, try unpluging it and checking the connection for corrosion. Mine was toast there was salt and water packed in it, replace it and it was fine. But, might want to get it scanned or checked first.

02-09-2008, 07:44 PM
Could also be a partially clogged fuel injector. You say it only happens under load.....if the PCM thinks it's running lean, it will pull timing like mad and the car will be very sluggish. The MAF sensor is another distict possibility though.