'04 GP rough start / stalling

[guitarfish]

My son has an '04 Grand Prix (no SC) that has had a starting problem for a while now. When you start the engine, it runs rough/struggles, does this all the time. Most times you usually have to hit the gas pedal for a second or so to help it out, otherwise it stalls. Once it "catches", there's a surge where it revs high for a few seconds, presumably from the added fuel.

The car has 98K miles on it. We bought it used a year ago, and inherited this problem. Yesterday we replaced the original plugs and wires with GM Delco iridium plugs and wires. The old plugs looked OK but the gap on them had widened to about .065". Even with the new plugs and wires, the problem remains. We also ran two doses of fuel injector cleaner, no change.

I'm not sure where to start diagnosing this. Any ideas would be greatly appreciated!

[ecartman]

Originally Posted by guitarfish

My son has an '04 Grand Prix (no SC) that has had a starting problem for a while now. When you start the engine, it runs rough/struggles, does this all the time. Most times you usually have to hit the gas pedal for a second or so to help it out, otherwise it stalls. Once it "catches", there's a surge where it revs high for a few seconds, presumably from the added fuel.

The car has 98K miles on it. We bought it used a year ago, and inherited this problem. Yesterday we replaced the original plugs and wires with GM Delco iridium plugs and wires. The old plugs looked OK but the gap on them had widened to about .065". Even with the new plugs and wires, the problem remains. We also ran two doses of fuel injector cleaner, no change.

I'm not sure where to start diagnosing this. Any ideas would be greatly appreciated!

Try cleaning the throttle body if it has not been done. I was having the same problem on my '04. I cleaned out the throttle body and the car has been fine for almost a year (and 30000km). Using throttle body cleaner and an old tooth brush or similar brush works well.

[guitarfish]

OK, I'll give that a shot. I cleaned a TB on my '02 GP last year, it was a job to get that sucker out! Hopefully the '04 is easier to remove.

Thanks

[ecartman]

Originally Posted by guitarfish

OK, I'll give that a shot. I cleaned a TB on my '02 GP last year, it was a job to get that sucker out! Hopefully the '04 is easier to remove.

Thanks

Yeah, the '03 and older models can be a bit of a pain but the '04 and up (Series III) 3.8L dont have the MAF sensor and screen built into the throttle body (or an IAC motor either) making it easy to do a good cleaning without removing the the unit. All that needs to be cleaned is the bore and throttle plate which are easy to access after removing the intake hose. Hope this helps!

[Firstymer]

I am faced with the same problem with my 00' GP se 3.1L. Even though I received the following code P0449, however, I remember someone attention that task to me ago. So, I should try cleaning the Throttle Body and the sensor? Do you have a picture so I can know what that is? and the exact procedure to perform the task?

[guitarfish]

To locate the throttle body, follow the large 6" diameter tube that runs from the air filter up to the engine. There's a large hose clamp at the end of that tube, and that's where the throttle body begins. On the 3.1, you'll see some cables on the side of the throttle body, one comes from the gas pedal, the other from the cruise control module if you have cruise.

There are several electronic modules on the throttle body on that engine, connected with small electrical plugs. The TB is bolted to the intake manifold with a few bolts.

On my '02 GP, I had to remove the TB from the car, and it was caked with pitch black crud (carbon I assume). Once I got all that gummy gunk cleaned out of it, it was so shiney you could eat off it (not recommended, LOL).

If you have basica automotive knowledge (which I assume you do since you're here), just take your time disassembling, don't force anything, etc.

As mentioned in other threads, regular carb cleaner can damage the MAF sensor. They make a MAF sensor safe cleaner, or you must remove the MAF sensor from the TB before cleaning. I used the safe cleaner, and cleaned everything.

Hope this helps.

[BNaylor]

Lets be careful with the advice given guys and make sure this solution would help cure his problem (P0449 DTC ???) which he has two ongoing posts at this time including no temperature gauge reading. He has a VIN "J" 3.1L engine so extra consideration must be given on throttle body removal since it has two external coolant lines, etc. He prefers pics if possible. .......

Originally Posted by Firstymer

I am faced with the same problem with my 00' GP se 3.1L. Even though I received the following code P0449, however, I remember someone attention that task to me ago. So, I should try cleaning the Throttle Body and the sensor? Do you have a picture so I can know what that is? and the exact procedure to perform the task?