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Old 11-08-2009, 09:23 PM   #1
SaturnSL2Guy
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Default Idle Air Control Valve

So I have a 98 Saturn SL2 manual. I have been having idle issues over the past two months or so, and they have gotten worse. When I slow down and come to a stop, my idle drops way below 500rpm and almost stalls, before it jumps back up to about 1000rpm. Then it bounces around until I start driving again. If I let in the clutch and let the car idle while im driving, the idle will jump up and down but it wont settle at any point. I will also have to idle get stuck around 2000rpm sometimes as well, and that wont stop until I shut off the car and restart. I have ruled any vacuum leaks already, because i replaced all hoses this summer. Can I assume that my IAC valve is bad? I dont want to spend $50 and realize thats not the problem. I have cleaned the throttle body and the valve before, and it is a simple fix, but I want to make sure that this is the actual problem. Your input is appreciated. Thanks!

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Old 11-08-2009, 10:23 PM   #2
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Default Re: Idle Air Control Valve

Yep, sounds like the IACV to me. clean it or replace it.

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Old 11-09-2009, 07:07 AM   #3
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Default Re: Idle Air Control Valve

Quote:
Originally Posted by SaturnSL2Guy View Post
So I have a 98 Saturn SL2 manual. I have been having idle issues over the past two months or so, and they have gotten worse. When I slow down and come to a stop, my idle drops way below 500rpm and almost stalls, before it jumps back up to about 1000rpm. Then it bounces around until I start driving again. If I let in the clutch and let the car idle while im driving, the idle will jump up and down but it wont settle at any point. I will also have to idle get stuck around 2000rpm sometimes as well, and that wont stop until I shut off the car and restart. I have ruled any vacuum leaks already, because i replaced all hoses this summer. Can I assume that my IAC valve is bad? I dont want to spend $50 and realize thats not the problem. I have cleaned the throttle body and the valve before, and it is a simple fix, but I want to make sure that this is the actual problem. Your input is appreciated. Thanks!
Could be other issues too. ECTS, bad stat, map and so on. Try an ects first and also note your engine temp

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Old 11-10-2009, 10:34 PM   #4
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Default Re: Idle Air Control Valve

Thanks, I think it might be the IAC. I had problems with it this summer jumping up to 2000rpm idle speed! I cleaned it out and everything was great for a while until now. I guess I should probably just replace it, it's only about $45 bucks, and this one seems to be cooked.

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Old 11-10-2009, 10:37 PM   #5
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Default Re: Idle Air Control Valve

Engine temp and everything else was normal, by the way. I went out yesterday while it was idling and fooled with the IAC wiring harness. I jiggled the harness and the idle jumped up and settled back down, and started to surge up and down until I shut off the car. I guess that it's definitely the culprit. Thanks for the help guys!

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Old 11-10-2009, 10:49 PM   #6
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Default Re: Idle Air Control Valve

Jiggle the TPS wiring also. They are real close on the harness and the TPS will do the same thing.

Might as well fix the broken one first.

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Old 01-22-2013, 04:20 PM   #7
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Default Re: Idle Air Control Valve

Problem here folks -

I had a really rough idle a few days ago to the point where I almost stalled, the SES light flipped on and for the first time to my eyes they blinked three or four times.

I've been reading in the forums that it might be a vacuum leak, bad IAC valve, gunked up EGR valve, PCV valve, etc.

I've replaced the IAC valve, cleaned the EGR and associated passageways, cleaned out the throttle body, tested the PCV and TPS, and replaced the IAC gasket, throttle body gasket and EGR gasket. I also replaced the hose that connects from the air intake tube to the top rear of the engine. Not sure the technical term.

The car on a normal drive is fine. At stops and in park it still coughs and surges. I am still idling between 1500-2000 RPMs and when I put the car in park it revs up to 3000 and slowly goes down.

Also I am about a 1/4 tank to empty. Over the past month I've been using a product called Heet that helps with cold winter starts. Maybe a fresh tank of gas will help smooth things out.. but is there a vacuum leak somewhere that I don't see or hear?

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Old 01-22-2013, 04:30 PM   #8
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Default Re: Idle Air Control Valve

Using Heet is not advised as it will end up causing rough running. Couple tanks of premium will get it cleaned out.

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Old 01-22-2013, 05:03 PM   #9
rTKEz452
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Default Re: Idle Air Control Valve

I won't be using that stuff anymore. I have to get my NYS inspection before the end of the month.. should I also replace the spark plugs?

I had a misfire code the other day when I had the computer read at Pep Boys but they also never cleared the codes to turn the light off. Should I get it read again and then turn the codes off this time? Would the computer still be functioning as if I had never done those recent fixes?

This time I'm actually going to write down the codes.. I know these guys have a lot to do and rush through it but I really want/need to know the specific codes that pop up.

Perhaps some long highway driving will clear the codes? I tried taking out the PCM B fuse to reset the SES but that didn't work.

Last edited by rTKEz452; 01-22-2013 at 05:09 PM..

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Old 01-22-2013, 06:14 PM   #10
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Default Re: Idle Air Control Valve

The codes won't clear until they are cleared by a scan tool or the requisite number of key-on events occurs without detecting the problem. That number is different for different codes.

A tank of gasohol (E10) will do as much good as most winter additives, assuming it's available near you. Ethanol is less damaging than isopropyl alcohol.

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Old 01-22-2013, 06:36 PM   #11
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Default Re: Idle Air Control Valve

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Originally Posted by virnin View Post
The codes won't clear until they are cleared by a scan tool or the requisite number of key-on events occurs without detecting the problem. That number is different for different codes.

A tank of gasohol (E10) will do as much good as most winter additives, assuming it's available near you. Ethanol is less damaging than isopropyl alcohol.
I'm going to take it in tomorrow to get scanned and to have the codes cleared. Now I'm thinking that it might be something electrical. I don't know if the IAC valve is even getting power. I plugged it into the connector and turned the car to acc and the valve didn't move in or out. I don't know if the TPS has power either. I don't have any sort of meter to test. I'll have to giggle things around tomorrow to see, or maybe its a busted fuse. I'm just rambling through all of the million possibilities so I can save some money at the shop. I just can't pinpoint this idle problem.

I'll stop at the gas station on my way too... I don't mind spending the extra money on premium. I'm going to stay away from additives for a little while.

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Old 01-22-2013, 07:11 PM   #12
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Default Re: Idle Air Control Valve

Now that I think about it, the new IAC valve that I just installed came out of the box in a contracted state, meaning the piston was all the way in the body. I didn't want to twist and turn the thing to get it to retract, but what should the new one look like and function like when its not connected to the car? I also tried hooking it up to the electrical connectors with the key in the acc position and the piston on the IACv didn't budge. This is stressful..

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Old 01-23-2013, 09:40 AM   #13
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Default Re: Idle Air Control Valve

Quote:
Originally Posted by rTKEz452 View Post
........I had a really rough idle a few days ago to the point where I almost stalled, the SES light flipped on and for the first time to my eyes they blinked three or four times. ......I've been reading in the forums that it might be a vacuum leak, bad IAC valve, gunked up EGR valve, PCV valve, etc. .......I've replaced the IAC valve, cleaned the EGR and associated passageways, cleaned out the throttle body, tested the PCV and TPS, and replaced the IAC gasket, throttle body gasket and EGR gasket. I also replaced the hose that connects from the air intake tube to the top rear of the engine. Not sure the technical term. ........The car on a normal drive is fine. At stops and in park it still coughs and surges. I am still idling between 1500-2000 RPMs and when I put the car in park it revs up to 3000 and slowly goes down. ........Also I am about a 1/4 tank to empty. Over the past month I've been using a product called Heet that helps with cold winter starts. Maybe a fresh tank of gas will help smooth things out.. but is there a vacuum leak somewhere that I don't see or hear?
Has the original coolant sensor been replaced with a brass one? Replaced thermostat too?

...
*The CPS is the heart of the entire EFI system. No cps = dead EFI system*
*There's more to a/c than just a few cans of refrigerant*
*There's more to brakes than just replacing parts*

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Old 01-23-2013, 07:51 PM   #14
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Default Re: Idle Air Control Valve

I have not yet checked the ECTS yet but my gauge seems to be reading fine. Old Nuc suggested I replace it with a brass sensor as well I just haven't checked to see if its crusted or cracked yet. I heard a lot of the plastic ones crack. I'm taking it to the garage tomorrow to save some frustration and to keep myself from freezing to death trying to fix this issue.

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Old 01-24-2013, 12:01 AM   #15
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Default Re: Idle Air Control Valve

Have you had a chance to stop at an auto parts store to get those codes read? They might give better direction for where to start looking for trouble than throwing parts at it. Misfire generally doesn't correlate with high or random idle so I'm hoping that wasn't the only code they found.

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