Ok, so over the last few weeks I've been having problems with my 99 Grand Prix idleing rough and stalling. I got it scanned and it threw no codes. Probelm went away for a week and then came right back. I've already gotten some CRC and cleaned both the MAF sensor and throttle body. After I cleaned it, it started up like it normally would before the problems. I started making my way to work yesterday and it was fine most of the way there and then it started choking up again. When I got off it started fine and I was making my way home and it started again. Whatever it is, its intermittent. One day/trip its fine and the next its throwing a fit. Ive tried cleanin the MAF and TB...could my MAF just possibly be bad? Should I look into another idle air control valve? I just know Im running out of ideas but Ive got the next two days off to figure it out and fix before going back to work on Friday. If anyone could chime in Id appreciate. Thanks in advance.

Try driving with the MAF unplugged, just don't go WOT when doing this. If the problem goes away, then the MAF is toast, if it stays the same, then at least you can now rule out the MAF.

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Thanks, I'll do that in the morning. Im hoping I can narrow it down without having to take it to a shop and have them a$$ joust me outta some coin for stuff I couldve done myself.

Keep us posted then we can start ruling things out and going down the list.

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Dubs:00 VW GTI VR6, Low and Slow 91 VW GTI 8v, Shave the Bay!! 91 VW Cabriolet 8v, bitch Basket
GP's:04 GP GT, Past now G-Ma's Girlfriend's 97 GP GT, "Project Pink Power"

Also possible the EGR valve could have some carbon buildup. I had this issue a few years ago as well. It did not throw a code until it finally bit the dust for good. If the MAF checks out then I would check that next. If there's some buildup then it's possible you can save it and not do like me and wait for the code to pop up when the valve completely keels over. I also had a coil pack have intermittent issues before it also bit the dust not too long after I got the EGR fixed. Just a few additional things to consider IF the MAF is still good.

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Alright so I unplugged the MAF and the problems still there. So we can rule that one out. If Im not mistaken I had my EGR replaced last summer but once this rain dies down I'll check that out too.

Be sure to check for vacuum leaks around the upper intake plenum, since they're known for cracking and warping, and the tube going from the EGR to the lower intake manifold, as it can also cause vacuum leaks. A faulty PCV Valve can cause problems as well. Here's a list of things to look at: Intermittent Engine Stalling Problems Hope that helps!

Ok, got the EGR off and I was right I mustve replaced it cus it appears almost brand new. Im gonna run through the list and check everything that I already havent ruled out. Thanks a lot for the help fellas.

Leaky fuel injectors or a bad fuel pressure regulator...or both. Sounds like it is loading up a cylinder, and causing issues.

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One Big Ass Mistake America

I was just reading about that in the list that I got the link for. How do I go about checking those?

Check your crank position sensor and it's wiring. Could be an exposed wire. This will cause such issues.

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Fast.Loud.Shiny

I checked the PVC valve and its supposed to be fine if it still rattles right? It rattled so I put that back. Also when I put the EGR back in idle was still rough. I unplugged it again and it smoothed out for a second only to choke up again. I did the same thing with the MAF and same result, smoothed out at first and then back to being rough. This weather sucks right now so everytime I get out there and do something it starts pouring again. Im trying to avoid taking it to the shop because it has a bad habit of being on its best behavior when I go and making a liar outta me. lol When the rain stops Ill check the Crank sensor next.

-- Wed Sep 28, 2011 8:22 pm --

Didnt get a chance to check anything else but i did have to go somewhere and while driving the car doesnt bog down at all once it gets going. Its strictly at idle. Could the idle air control be the culprit?

I was just about to say what about the IAC motor, but it looks like you're on the right track anyhow. The FPR could also be causing some issues for you.

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Sold: 06 Cobalt SS/SC, 99 GTP 245WHP/326 Ft-lbs, 06 R6

A bad IAC motor is supposed to set a check engine code. Unplug it, and see what happens.

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One Big Ass Mistake America

Yea thats been the part thats giving me the flux is that it isnt setting any codes. Weathers clear today so Im about to go out and get on top of it now. I'll keep you guys updated

Started my car this morning with the IAC unplugged and it idled at about 1500RPMs. Plugged it back in and idle went down to about 1100RPMs with no hesitations, but there did sound like there was some restriction in my exhaust. Whats got me even more confused now is that the cars running fine all of a sudden. Possible catalytic converter issue?

Its been like a week since Ive been back on here. Ive been driving my car back and forth and what Ive been having to do is when Im at a light or when traffic isnt moving, I have to keep my foot on the gas while braking or throw it in neutral and keep the RPMs at about 1100.

so the RPMs are dropping out and the cars stalling when it's not in gear? Thats odd, mine had a stuttering problem like that at stops but after i scrubbed the hell out of the TB it's fine (now if only these friggin vibration would go away -.-) i would recommend checking around the throttle body again, i had a black house that connects to the MAF i think it was, and it was disconnected the whole time, i'd just re-check all of the connections again, as for another idea, when you start your car does it jump to like 1500ish rpms?

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BRAP BRAP BRAP nuff said

Yea its stalling out when it is and isnt in gear. I scrubbed the sh!t outta the TB twice, recleaned my MAF and it still throws tantrums at idle. When I first start it up, I could be wrong, but I think the highest Ive seen it was at like 13/1400ish. I'll make sure to check that out when I go to the gym in a couple hours

Dude, vacuum leak. Check all your vacuum lines for cracks and replace as necessary. Done.

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Yeah, I would tend to agree with this diagnosis over my previous post, though if you're pulling stuff apart, it wouldn't hurt to clean the IAC motor.

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One Big Ass Mistake America

alright update...I kinda feel like a moron and a dirtbag. I started my vacay from work today and decided to track down this problem while i had the time. While i was spraying the carb cleaner around trying to find the leak I noticed the idle change when I sprayed around the EGR. I heard the hissing first and when I reached over and sprayed, I looked down and a nut was missing off of the EGR. I put it back on and tightened em both up and started the car...and wadya know, it idles at around 800/900 RPMs on its own for the first time in months. Could the EGR not fitting flush have been the culprit. Although not a leak from a line, that air escaping is pretty much the same thing right? It even starts and idles fine when I remote start it now which I havent been able to do in months.

I would say that was def your problem, basically a vac leak which would have gotten worse at cruise when your egr was opening.

Yea, I think Im good to go now. I drove my car several places for a while today and it idled fine at every light, stop sign, etc. Now to get my tune-up, hub bearing and control arm bushings outta the way and Im good to go for the upcoming winter. Oh btw, just unhook my neg batt cable for a while to reset the computer so it'll stop guzzling up my gas right?

Back to the drawing board 'cus yesterday and today I went out to start my car and it had the same issue again. Its throwing me off now because yesterday when it did it, I went out and tried again like 1 or 2 hrs later and it was fine. I drove it to go play football and back and a few other places and it gave me no problems. Should I be looking for the same things I was looking for before or is it something else?