Rough idle and sluggish

I have a '95 grand prix gtp with the 3.4 DOHC. Whenever i come to a red light, or stop for a little bit, when i take off it kind of sputters untill i get above ~1200 rpms, then it is real smooth. But the odd thing is, when the engine is real warm like 180-190-200 degrees, i can come to a stop for a minute then take off and it's just as smooth as it can be. Also when my car is idling, i can just touch the gas peddle barely and completely take my foot off and it revs up to about 1100 and sticks there for about 10 seconds, then slowly eases down to 800-900 rpms (and sometimes sputters and/or fluctuates between around 550-800 rpms, it even just died one time.) Im guessing maybe the IAC valve and TPC maybe even EGR valve problems. Thanks ahead of time for Any suggestions.

sry, not TPC, i meant TPS (throttle position sensor) lol

Could be a problem with the MAF,try unpluging it when the car is cold and see if the problem goes away.


~Larry~

ahh, ok, i never thought of that, i will try it and let you know what happens

ok, i tried that, and the engine would idle at about 600 rpms barely runnin and when i'd tap on the gas it would still stay barely revved up over 1k for about 10 seconds and then idle back down :(

Hello,

This just happened to my sister-in-laws '95 GP. Likely you have a clogged fuel injector. You need to go to a GM dealer parts counter and buy GM part #1050002 Top Engine Cleaner 15 oz can. This can states it is a carb/engine cleaner, but you can pour it into your gas tank. We had a half tank of gas when we installed this. Within 25 miles, problem solved and engine sounded as smooth as silk. It had sounded like it was running a cylinder short and was bucking. I was told that Seafoam also would work. I bet this is your problem.

John R

Ah, awesome, i will try that and let ya know how it goes.

I just noticed that on the rear right side of my intake, the little black vacuum box where two different vacuum hoses go in to it (not the one that is actually a sensor) but the one that bolts right in to the side of the intake right there, ....well the metal one looks like it is just sitting in the hole where it is supposed to be on with a rubber connector, LOL. would this cause some idle problems? j/w, cuz ima get that replaced asap. (anyone know what it is called so i can save some time of searching for the name?)

Oh, That cleaner is about $7.00 a can. It is ackward to pour into the tank but I am sure you can manage. By the way--what's the mileage on the GP? The other issue is the condition of your fuel filter. If you have over 50,000 miles and it was never changed---that might be part of it too.

John R

the mileage is almost 119,000. and the fuel filter is new, i recently changed it in hopes of that helping too, lol. But im not sure really where i can get that cleaner. I live in Corinth, MS, and not really sure where around here i could get that, unless O'Reilly, Autozone, Advanced, or NAPA would sell that?

Actually, i think Brose and Copeland automotives here are GM dealers, i will check there.

Oh, this is off the subject, but i just thought of this....i cant figure out what the bolt is called, but i will try my best to describe it. OK, imagine lookin under the car, and the rubber boots (like 4-6?) that hold basically the whole front end on the unibody. ....well whatever bolt that is, i am missing one on my driver side. I talked to autozone and they said it would more than likely have to be a dealer item, so if anyone could let me know what that bolt is called i could ask the GM dealer about buyin one. Thanks.

are you taling about the subframe mount? if your missing that. get it replaced soon.

one other thing i would check is your idle air controller.

yea, that sounds like the right bolt. i will ask about that too. and i will check the idle air control valve as well.

Ok, i just got the Top Engine Cleaner today, and i bought a set of spark plugs, and as soon as i get oil and filter i will do all of this and let you all know how it goes. I read at another place that the spark plugs could foul and a fresh oil change would be needed after running this through the engine, but i dont know where to put it, lol, gas tank? oil filler? ? anyway, i will be searching, if anyone knows plz post it, maybe itll save me some long searching. Thanks ahead of time ( This is for the 3.4L engine, remember, not sure if that makes a difference, but doesnt hurt just to be sure, lol)

I think i might have to do it through the brake booster line.

Hello TWSTICE,

I guess I should have said--yes I ran this stuff through my sister-in-laws fuel injected small 6 cylinder 95 Pontiac Grand Prix--on the advice of a auto knowledgable coworker. The result was positive and I put the whole can into her half full tank because the car needed something done asap--problem solved. I just this week put a second can into my 5.0 liter Lincoln. No adverse result there and it seems to run smooth--it had been idling a little rough at some times. Who told you to change the plugs and oil? I am going to check that comment out. I dont believe that is necessary.

John R

Ok, i just got the Top Engine Cleaner today, and i bought a set of spark plugs, and as soon as i get oil and filter i will do all of this and let you all know how it goes. I read at another place that the spark plugs could foul and a fresh oil change would be needed after running this through the engine, but i dont know where to put it, lol, gas tank? oil filler? ? anyway, i will be searching, if anyone knows plz post it, maybe itll save me some long searching. Thanks ahead of time ( This is for the 3.4L engine, remember, not sure if that makes a difference, but doesnt hurt just to be sure, lol)

I posted an answer before this one---I missed your point. I followed a coworkers advice and poured the can into the GAS TANK. I suggest this route and no other. The can states carb cleaner and obviously there is no carb on injected cars to pour this stuff into. I think it is risky for you to do anything else with this cleaner (than the gas tank method) unless you have a mechanics approval--I am not a mechanic and you choose to act on this at your own risk. I was only directing my answer for the rough idle and miss (injectors). If you need to clean the engine, consult someone else before using this stuff for that purpose. Pouring this stuff into the gas tank limits it to cleaning in measurable quantities and minimizes risk of damage and/or any injury to you!!!! (Yes, pouring this stuff into the oil will dilute the oil and require an oil change if that is your intent).

John R

Well i read directions on how this stuff is usually used. it is like sucked in through the intake (about 3/4 a can) at a medium idle, then let the car idle on its own till it dies, let it soak for about 20 minutes, start up the car again and pour the rest (if any) in to the intake. (more than likely through the brake booster line on my engine). Then drive the car (aggressively) untill the massive amount of smoke is gone, then do a fresh oil change. and if ur spark plugs are old, they may need to be changed as well.

Ahh, i see. The gas tank method sounds good to me, i think i will do this. one question im just wondering, does this stuff cause any smoke or rought running while its in the gas tank, or does it just smooth right out?

actually, the easyest way to do it is have it feed in through the brake booster's vacuum line. the only thing you have to do for the stuff is feed it through a constant vacuum line at idle. and the break booster is usually the easiest to get.

SUERED, thanks man, i put the top engine cleaner in the gas tank and it doesnt spit and sputter when i first take off now. So that fixed the sluggishness, now i just need to fix how the rpms will stick up at 1200 and eventually rev down to idle. I bought an Idle Air Control Valve today and i will put it on tomorrow, im hoping that will fix the problem. I'll let ya'll know how it goes tomorrow.

i apologize if that isnt the case. but could even be the throttle position sensor. remove your mass airflow sensore and clean that off with some carb cleaner and reinstall that.

Ok, i will try all that and let you know if i figure anything out. Thanks.

I have a felling your just dealing with bad Fuel injectors 119,000 miles and probley not to much fuel injector cleaner ran though it in the last 10 years. But replacing fuel injectors could be $$$ but i have a 98 GTP and I run Fuel injector cleaner in it every other fill up with 93 octane gas

I havent tryed this method my self but i was told by a machanic that a pint of Tranmission fluid put into you gas take cleans out those fuel injectors to brand new you can try this if you dare could help alot this guy does know his shit

Hey,

If you are brave, they do sell induction fuel rail cleaning kits, but by the time you finish with those, I bet the expense will run nearly $50? That brings the injector cleaning to home plate. Or...gamble with another can of cleaner. I personally dislike putting any cleaner in a gas tank (just did it with my car) because I heard tales that---yes the cleaner also cleans your tank--guess where that crud goes?!

JR

I have run fuel injecture cleaner in it a few times. and i also ran that top engine cleaner in it. The rough idle and sluggishness is gone now. But the other problem still remains. When i tap the gas peddle it revs up to about ~1200 rpms and in about 10 seconds it settles back down to idle. Im thinking it might be leaky EGR valve, because i replaced the intake gaskets around when i first got this car and i only replaced one of the two EGR valve gaskets. I ordered the two gaskets and they will be here tuesday. I'll let ya know how it goes.

after replacing the EGR valve gaskets, the problem still remains......tap the gas pedal and the engine revs up on it's own to about ~1200 rpms and settles down eventually in 5-10 seconds. I am completely stumped now, if anyone have any more suggestions plz post em, and thanks for all the other help.