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2020 February
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coulomjo

Rough/low idle on the GA

Question

coulomjo

Hey guys,

I'm having a rough idle on my '99 Grand-AM (2.4L). When the engine is cold it idles at 700rpm but after it goes down to 500-550 and that's when for instants it seems like it's choking. Is there any way to raise the idle?

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dangerranger67

this sounds like a question for chaos however.. if is never advised that you raise or lower your idle manually as if your car is having an incorrect idle its a sign that something has thrown it off.. by adjusting you idle manually without a tune you could be throwing more out of wack

i woudl start with some basics, and normally fuel system tune up..

i am not familiar with the cold start systems on these cars but if there is a cold start sensor or engine coolant temperature sensor i would check those to..

but this is just some basic stuff as i said i am still new to pontiac and GM myself! my guru-ness rests with Ford and Toyota haha

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AtomicPunk

any "engine lights" on or anything? how much fuel is in the tank? are you SURE that theres gas in there? pull a spark plug, how does it look?

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coulomjo

No engine lights, doesn't matter if the tank if full or not. Plugs are almost new and are in good shape. I've even cleaned the ICV and at first its seemed that it was doing better but the problem never left.

It still could be the ICV doing a bad job. I also read on the net that a bad vaccum seal can cause the engine to receive less air and cause it to choke momentarily.

I'll try to take a look at it this week-end, see if I can identity the problem.

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dangerranger67

easy solution to test for vacuum leakage is to spray some brake cleaner or something along those lines in and around your vacuum lines.. if shes got a hole or a broken line.. it will tell you!

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Silversmok3

Hey guys,

I'm having a rough idle on my '99 Grand-AM (2.4L). When the engine is cold it idles at 700rpm but after it goes down to 500-550 and that's when for instants it seems like it's choking. Is there any way to raise the idle?

Open your hood and look down at your intake manifold. On the front, facing the front bumper is a small 3" vaccum hose that connect two lines , it looks like a U when your looking at it. This line cracked on me last year,a big hint is that when it was windy the idle problem got worse ( which lead me to check my CAI, IAT, and intake manifold sensor B) ). The motor was good until it got to about 600 RPM, where it died immediately. Got real good at brake tourqing at 1K until I found the problem.

50 cents worth of tubing later, problem solved.Let us know if that fixed it.

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coulomjo

Open your hood and look down at your intake manifold. On the front, facing the front bumper is a small 3" vaccum hose that connect two lines , it looks like a U when your looking at it. This line cracked on me last year,a big hint is that when it was windy the idle problem got worse ( which lead me to check my CAI, IAT, and intake manifold sensor :lol2: ). The motor was good until it got to about 600 RPM, where it died immediately. Got real good at brake tourqing at 1K until I found the problem.

50 cents worth of tubing later, problem solved.Let us know if that fixed it.

You know what, that could be exactly my problem. The tube is all cracked in different places. I'll stop at Canadian Tire this week to get a replacement tube.

I'll update you guys when I change it.

Thanks!

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dangerranger67

WHOAH i didnt even notice your canadian lol i was WTF there no crappy tire in the southern provinces :rofl:

anyways hopefully checking on that helps though

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coulomjo

Sorry guys, didn't have time to update this tread lately. So 1.49$ later I I changed the hose and it's still doing it but not as brutal as before and the engine seems to run better. I guess the hose was part of the equation but not the answer...

Anyways it's a lot better thanks to your suggestions so I wanted to thank you for pitching in! :lol2:

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coulomjo

It's been 5 days now and I have "Service Engine Soon" lit up since Tuesday... Also my choking problem is still as bad. :D I've cleaned the ICV back in March because it was doing it... could it be that the valve is no good?

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Rodimus_Prime

most if not all idle issues are caused by some type of vac leak

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coulomjo

Hmmm.... that reminds me of something... the seal between the engine block and the intake resonator (that plastic box in front held with 2 bolts, at least I think it's a resonator) is dry and bits are missing... could it be the problem?

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Rodimus_Prime

if its in the front of the engine and plastic bolted to the intake side of the cylinder head thats your intake manifold, and there should be alot more than 2 bolts holding it on

is this piece you speak of before or after the throttle body (where your throttle cable is hooked up to)

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Kman

Yes, idle screw is under the throttle body,  hex head. Easiest to adjust when taking the throttle body off. Tighten to increase idle and loosen to reduce idle. 1.25 turn I feel is good adjustments. Pontiac grand am years 1999-2005

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