Big problems with my parents Grand Am SE,. help please

[Mac]

I was pointed here from another web board.

`94 grand am se , 3.1L V6

It drives fine untill its warm, but once it's warm it stumbles all over itself. Driving along/accelerating/whatever, if you have your foot on the gas, it will cut out for 5 or six seconds then kick back in again. Sometimes it only cuts out for a few seconds, but does it a few times in a row so it gets all jerky. It's stalled a half dozen times now after doing it, but doesn't stall all the time.
Repaced the coolant temperature sensor yesterday, no luck. Replaced the plugs and wires (one wire was broken, one plug was cracked) this morning. Not much luck either, it's still doing it, just not as much.

I have no idea what's causing this. The only thing the computer pulled up was an O2 sensor code, but i'm guessing it's an old code since the sensor was replaced a few weeks ago.

Thanks for any help you can give me

[Homer]

First of all delete that O2 code. Just to see if it comes back up again. 2nd thing is to do a visual inspection for and broken/cracked or missing vacuum lines. But it sorta sounds like maybe a map sensor, autozone will test it for free if you bring it in.

[KBworldHQ]

It's the Throttle Position Sensor. I had a 94 GA 3100 a few years ago that had the same problem. Lucky for me, the car was still under warranty and I didn't have to pay the $270 the dealer charged. I'm not sure how much the TPS costs for just the part (try looking up the part at carparts.com) but changing it is relatively simple. Pick up a Haynes or Chiltons manual for the GA while you're at the parts store, it will point you in the right direction (that is if you don't have one already.) Good luck...

[Anonymous]

could also be your IAC..

[Mac]

It's the Throttle Position Sensor. I had a 94 GA 3100 a few years ago that had the same problem. Lucky for me, the car was still under warranty and I didn't have to pay the $270 the dealer charged. I'm not sure how much the TPS costs for just the part (try looking up the part at carparts.com) but changing it is relatively simple. Pick up a Haynes or Chiltons manual for the GA while you're at the parts store, it will point you in the right direction (that is if you don't have one already.) Good luck...

Since the wires/plugs didn't completely fix it, I've been thinking TPS. Changing the parts myself isn't a problem at all, just diagnosing it is becoming a pain.
Theres a testing procedure for the TPS in the haynes manual, is this a good procedure or is there another better way to test it?

[Mac]

First of all delete that O2 code. Just to see if it comes back up again. 2nd thing is to do a visual inspection for and broken/cracked or missing vacuum lines. But it sorta sounds like maybe a map sensor, autozone will test it for free if you bring it in.

I take it disconnecting the battery for a few minutes will reset the computer in these cars? I'm not too used to working on them.

[wiccanferret]

First of all delete that O2 code. Just to see if it comes back up again. 2nd thing is to do a visual inspection for and broken/cracked or missing vacuum lines. But it sorta sounds like maybe a map sensor, autozone will test it for free if you bring it in.

I take it disconnecting the battery for a few minutes will reset the computer in these cars? I'm not too used to working on them.

You are correct, sir.

[Mac]

First of all delete that O2 code. Just to see if it comes back up again. 2nd thing is to do a visual inspection for and broken/cracked or missing vacuum lines. But it sorta sounds like maybe a map sensor, autozone will test it for free if you bring it in.

I take it disconnecting the battery for a few minutes will reset the computer in these cars? I'm not too used to working on them.

You are correct, sir.

thought so, some cars are weird and theres a stupid round about way of resetting the ECU.

[Mac]

also,. the Idle Air Control Valve is REALLY hot to the touch, like to the point where you cant touch it. When the car is running. I took it off yesterday and it was quite gummed up, and looked like the plastic plunger piece was burnt in places.

Could this be causing any of my problem?>

[Anonymous]

Clean your IAC with throttlebody cleaner (clean the whole throttlebody for that matter). Made a world of difference on my engine, from surging and stalling to running nice and smooth.

[bszopi]

If the IAC is hot and gummed up, then it probably isn't able to move back and forth. The reason it would be getting hot would be because it's attempting to move the pintle, but isn't able to, but it continues to see a bad position. Not sure if it would be able to be cleaned up enough to get it to work correctly, so you might just have to get a new one. Your problems should be solved then.

[Anonymous]

If the IAC is hot and gummed up, then it probably isn't able to move back and forth. The reason it would be getting hot would be because it's attempting to move the pintle, but isn't able to, but it continues to see a bad position. Not sure if it would be able to be cleaned up enough to get it to work correctly, so you might just have to get a new one. Your problems should be solved then.

I soaked mine in jar of gas!

[Mac]

If the IAC is hot and gummed up, then it probably isn't able to move back and forth. The reason it would be getting hot would be because it's attempting to move the pintle, but isn't able to, but it continues to see a bad position. Not sure if it would be able to be cleaned up enough to get it to work correctly, so you might just have to get a new one. Your problems should be solved then.

I soaked mine in jar of gas!

lol,. i cleaned the shit out of it with brake cleaner, I love that stuff Between me and the other mechanic we'd go through like a can of it a day lol. but like I said, it was burnt up inside and VERY hot to the touch when running. Bought a new IACV tonight, hopeflly that'll cure it. If not, then the TPS, if thatd doesn't do it, then a can of gas and match.

[DarkKnight]

The very same thing happened with my Z24. (not the IAC, just the cutting out, etc.) Have you checked your ignition at all? In my case, when the engine warmed up it caused the ICM to malfunction. At first it would just cut out under load (like 60% throttle or more). Then the problem progressed rapidly to failing under any throttle, stalling, and becoming jerky. It was basically exactly as you are describing it. Eventually the ICM failed all together leaving me stranded. Once the engine cooled down for an hour or so it would restart fine, and run great until the engine got warmed up. I ended up replacing the ICM 4 times before the problem eventually went away. I also tried swaping the ECU for another unit as well, it didn't fix it. The dealer had an extra part that goes between the ICM and the coil packs. That part combined with a very good heat sink grease finally cured the problem. Or at least it went away after that last time. I had my car for another 3 months then my timing chain snapped. I think my engine was trying to tell me that 212K mi was enough! Good Luck, it took me a month before this was finally fixed.[/u]

[RLJ]

You may also want to check for a shorted fuel injector. When I had one go, It did almost the same thing. Start ok when cold, run for a few minutes, then run bad, and either cut out under throttle, or die completely.Didn't throw any codes either.
It killed an ECM on me before I finally found it. Once I did & replaced it. All was well.