Not an SVX question, but important!!!
 

Well this is an interesting one. As I said in another post, I have Mandi's SVX this week because she took my car home to get fixed. I have a 1996 Grand Prix GTP with the 3.4L V6. Here's the problem. Starting this fall, when i went to start the car cold, it would fire right up, but without me touching the gas, it would jump right to 3000RPM, then RPMs would fall fast until it stalled. I have to keep touching the gas to keep it running, and everytime i just barely touch the gas, it goes ballistic...3000-3500RPM...then right back down again to almost stalling. It does this until the engine warms to about 120 degrees. Then it's perfectly fine. Like i said i sent it home to get fixed, well the shop said there is NOTHING wrong with it. They ran a computer diagnostic and a "hand" diagnostic and they said it runs like new. GREAT. So i know i will get this car back and it will do the same damn thing it always did. But im sure it didn't do it when they checked it out.

So does anyone have any clue what could be the problem here? I am thinking i will try some injector cleaner to see if that helps.

My only other thought is...maybe this is an effect of the engine being accustomed to a higher octane fuel? Of course i bought it used and i have no clue what the dude put in it before me...so i put in 89 oct. If he put in 93 and i put in 89 now, could it have that effect?

Thanks for any help you can give.

Shadow, a couple of things, although they are SVX based, I would think they would be similar.

I believe your GTP is equipped with a Mass Airflow Sensor (as are most cars these days). It could be the culprit and just be "acting up" intermittently. Also, you may try removing your negative terminal on the battery overnight to re-set the ECU (not sure this works with Pontiacs, but, it can't hoit :) ) That may take care of any "learning" the ECU has done under higher octane performance. Again, these are just guesses.

Agreed, sounds like a bad sensor. My guesses would be your mass air or an oxygen sensor. My Sunfire had that kind of problem as well turned out to be a bad o2 sensor. Mind you I also kept getting a check engine light when it did it. :rolleyes:

Ryan

check you TPS (throttle position sensor) same thing happend on my buddy's grand am, and thats what fixed him.

1996 the main culprit like mentioned above would be the throttle position sensor. To reset the computer disconnect it for 15min, usually how long it takes me. My 96Z28 has the same ODBII computer just different program. There's alot of info on some GTP forums and camaroZ28.com.....its all GM there. Too bad you dont have the new SC 3800's. With some simple mods they are capable of low to mid 13's :) Good luck

Thanks...
 

I will try the disconnect thing tonight when my car gets here...thanks alot.

And to think people have occasionally called us "snooty" and "exclusive" and unwilling to help anyone except those who ask SVX related questions. What a great group. The spirit of cooperation is awesome. :)

Re: Not an SVX question, but important!!!
 

Try cleaning the idle air control valve. I could see how it getting stuck could cause your problems. My wife's Legacy exhibited a different set of symptoms, but I think the same problem might be the cause. My reasoning:

IAC is closed when throttle is opened. If you let off the gas and the IAC sticks shut, it could stall the car.

It's a guess, and probably not a good one, because it doesn't explain why your car only does this when cold and why your revs jump so much when you touch the throttle.* That right there leads me to suspect the throttle position sensor, which I doubt is cheap.

* No, wait, it might. If the IAC stuck open when throttle was applied, would the O2 sensor tell the car to add fuel to this now-lean mix?

FIXED!!!!
 

Well I disconnected the battery today for a half hour...then went back and reconnected it. It started perfectly. Couldn't even tell the engine was running!!! Thanks to everyone who posted on this. And JC Z28...i had started out looking for a 97 or 98 GTP with the SC 3800...but changed my mind quickly after i saw the reliability ratings of those things. My cousin had a 97 and my brother's friend had a 98...both were in the shop about once a month. From my experience, and what i am told by GM techs, the 3400 is a better engine. And who says I can't get mine to do 13s? It will cost a bit more though!

Hey shawdow maybe you could even find a busted up McLaren Turbo......Swap em in, boost it up and take off. Is that 3.4 the twin Cam motor they used on the Z34's? Speaking of reliability of the SC3800's i'am actually a bit suprised to hear that they've had so many problems....i hear the eaton units and the engine itself is very stout, i have a 1998 Regal LS with the 3800 NA and its suprisingly quick with not one mechanical problem to date. I guess it all comes down how you feed it and treat it.

i think it is the tps too.
 

in fact i am about to replace mine. i replaced my idle air control valve/sensor and it still does the idle thing a little. i would check there first.