IAC Valve

Misanthropy

Misanthropy

Information Junkie
So I got my part changed, shown in the picture below.... that stopped the exhaust leak. The car still idles rough. Checked and replaced my vacuum lines, ran some sea foam, cleaned my MAF sensor, changing my DPFE sensor and adding a new harness, Replacing my EGR vacuum regulator, and checked my egr valve. Along with this I am going to take my throttle body off and clean the built up carbon out of it. Not sure if this will help with the rough idle or not.

So here is my question... after doing all of this, should I go ahead and replace my Idle Air Control Valve? Also, should I check the WOT position and my plat positions? It only runs rough at an idle... Tries to overheat at a drive.
 

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What he said. Best time to do it if you ever do. But careful how you clean the TB, use TB cleaner. There is a film that need to stay on the TB. Some say it can be cleaned off, other have example of it being done and the vehicle runs horrible.
 
unity said:
What he said. Best time to do it if you ever do. But careful how you clean the TB, use TB cleaner. There is a film that need to stay on the TB. Some say it can be cleaned off, other have example of it being done and the vehicle runs horrible.
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Yeah I saw the warning on the outside of the throttle body, I cleaned it anyhow with a cloth and tb cleaner. If it ends up being lame, is there a way to have it resurfaced?
 
Misanthropy said:
Yeah I saw the warning on the outside of the throttle body, I cleaned it anyhow with a cloth and tb cleaner. If it ends up being lame, is there a way to have it resurfaced?
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No. But if you were gentle and used TB cleaner you should be good.
 
I didn't replace the IAC, but the car still idles rough. Any other suggestions? I don't think the IAC would make this big of a difference. It only idled rough after my new tranny was put in. Could it have something to do with this?
 
Have you checked your vacuum at idle and systematically checked for vacuum leaks?
 
driller said:
Have you checked your vacuum at idle and systematically checked for vacuum leaks?
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Neither. What would be the best way to check for leaks in the vacuum lines besides taking everything off ? What tool do I need to check my vacuum at idle? I might just have the shop do it.
 
You can get a vacuum test gauge and some fittings, plugs, etc... at any parts store pretty cheap. Most test guages will come with instructions simple enough to follow.
 
Thanks Driller. I will do that tomorrow and check it out. I will also post a link once I take a short video of Irene at an idle.
 
I do not believe that would be caused by the IACV. If it is a vacuum leak, it doesn't appear to be large. Have you done a vacuum test?

Cold idle is mainly affected from the ECT and TPS sensors while warm idle is basically a closed loop process based on the O2 readings but the ECT does come into play.

Does it seem worse at cold or warm idle? Or does it seem the same? If it's worse at cold you may suspect the ECT sensor or something ignition wise. If it seems worse at warm idle or the same, I'd suspect something wrong with the A/F ratio which could be anything from a dirty induction, a vacuum leak, tired O2 sensors, dirty fuel injectors, etc...
 
One thing that would lead me to believe its a bad (sticky) IAC valve is the fact that you started the car and it did NOT idle up appropriately. It should ALWAYS jump up to 1200-1300 rpms and then drop down to idle speed of 800-900 rpms. The fact that yours didn't do that makes me think the IAC is bad. Its probably stuck almost shut which is causing a funky idle like that.

If it were my car, thats where I would start, minus the fact that its a PITA to get to, its not an expensive part. You could also try unplugging the IAC valve and see if the idle does the same exact thing or if it idles higher/lower. If it stays the same, then your IAC is bad.
 
If that was a warm start, I disagree.

If that was a cold start - yes it should've idled higher at first.

I assumed it was a warm start.
 
whens the last time the car had a full blown tune up? 161,000 miles is enough in itself to make any car idle rough. i would change plugs, wires, pcv valve, air filter, fuel filter, iac and tps. sure it seems like alot to do and might cost a little bit, but some of those may be original, and thats no good.
 
driller said:
If that was a warm start, I disagree.

If that was a cold start - yes it should've idled higher at first.

I assumed it was a warm start.
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Go start your car after you've warmed it up, I guarantee the idle doesn't gradually build like it did in his video. It should jump straight to 900-1000 rpms and then drop after a second. His was almost a gradual build up like the car was actually slowly building up its idle, haha. Watch the vid again.
 
I didn't test the vacuum, gunna let the shop do that this week.

I have replaced... Vacuum regulator, DPFE, PCV valve, ran sea foam before I changed these, also cleaned the MAF sensor and my air filter. Plus I just had the fuel injectors cleaned and fuel filter replaced. If I really get on it then the check engine will come on for a minute.

The video was a cold start. It seems to idle fine for about 6-9 seconds then starts dropping off and jumping.

Oh and I bought the car at 125 and had the plugs/wires replaced (lifetime wires from kragens) at 136. I am about due for new plugs, but I am wanting to be sure what is wrong. Only because I am already over budget (7K so far in the previous shop trip) and only 1300 of it was labor :)


Jesse, if I was to unplug the vacuum going to the IAC and the idle stayed the same, then the IAC is bad ? or is it the opposite?
 
Misanthropy said:
The video was a cold start. It seems to idle fine for about 6-9 seconds then starts dropping off and jumping.
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Dang....if that was a Cold Start then you def. got a problem. :)

Misanthropy said:
Jesse, if I was to unplug the vacuum going to the IAC and the idle stayed the same, then the IAC is bad ? or is it the opposite?
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First off...its not "vacuum powered", it has an electrical plug. If you unplug the electrical plug and start the car and it does the exact same thing, then your IAC valve is definitally bad. If the idle jumps way up to 1200-1400 rpms then it IAC is good.

budpytko said:
SeaFoam has been know to destroy plugs....and as your are already old, it may be your problem!
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Jarrod....if you've done a SeaFoam treatment AND had the boys do the fuel injector service and you didn't change the plugs afterwards, I would definitally start there. Like Bud said, SeaFoam does wonders on your engine, but you plugs are doing all the work and taking the brunt of the junk that is getting cleaned out. That goes for the fuel injector treatment too.

Change the plugs first, then test the IAC valve.
 
Replacing IAC, EGR valve and TPS sensor tomorrow. Took it to a hole in the wall shop and his reader kept saying egr valve. He didn't charge me either :) I will do the spark plugs right after that (even if my idle goes back to normal.)
 
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