Rough Idle / IAC Questions

[Heg87t]

Hi all,

Still struggling with a rough idle. Car is rich and stalls at idle. I have done the IAC reset and also tried adjusting the throttle stop screw to get 20 on Turbolink but no luck. The IAC numbers will come down when I turned the screw in but after a minute go right back up to over 100. I turned the screw all the way in until the spring was tight.

Questions:
I took off the IAC to see if it needed cleaning. It looked fine. I checked my manual and it says that the pintle should not be extended over 1.125". Mine was over this so I screwed the pintle back in about 0.25”. I put the IAC back into the mounting block and grounded the ALDL to make sure it was working. It extended fine and is over 1.125” again. Is the 1.125” dimension just for when you are first installing the IAC to prevent you from crushing it or should it be less than 1.125” anytime it’s at rest? Are there any bench tests for the IAC? It is the metal bodied valve which I think is original and the car has never idled right even before the rebuild.

I am going to replace all the gaskets on the throttle body to make sure there are no vacuum leaks put it back together and try it again to do the reset procedures.

I was also going to cap the vacuum line to the EGR valve to eliminate that as a possible problem or leak. I have capped or removed all the vacuum lines except the fuel pressure regulator and one line going to my 3bar MAP sensor for Turbolink.

Any other ideas to get a better idle?

 

[Just a Six??]

Maybe time for a new IAC?
Have you ever had a screwy power surge to the ECM? They use a separate driver for IAC & I have one here that works perfect other than IAC numbers always look crazy even tho car idles great & runs fine. Other ECM & the IAC numbers are good.

 

[Heg87t]

ECM problem is an interesting thought.

I will put that on my list of items to try. I might just break down and put a new IAC on it. I just hate to throw parts at a problem without understanding why.

Still seems weird. The car runs pretty good once it is off idle. Just won't idle on it's own.

 

[pajo]

no idle

Did you ever get the problem figured out -- it does seem as if you have a vacoom leak or bad iac..?

 

[Heg87t]

Hi,

I did get the car back together. I replaced the EGR with a new gasket but capped the vacuum line a the metal tube to eliminate it. I reset the TPS and fired it up. The car ran great then. Had a minute of fast idle then it settled down and idled on it's own. Took it for a ride and it was noticably better. Brought it back after a warm up drive adjusted the screw to get 20 IAC counts and tweaked the TPS to 44. Thing idled well. I pulled and plugged the vacuum line the fuel pressure regulator and the idle cleaned up more with the higher pressure so I adjusted the pressure up to the 45 recommended for the chip.

In conclusion, I am not sure if adjusting the IAC helped or removing the EGR. Drove it today and it started up and idled well until it sat for about 3 hours then it would not come off of the higher idle speed and stalled after I stopped for gas. I am still perplexed. I have not reset the computer for a while when working on this. I may pull the battery next and see how it does.

I do have a problem at WOT now... I need to fix the spinning the tires in second gear thing!!! :biggrin: Hmm... got to get that posi installed.

Dave

 

[pajo]

egr

it almost seems to be that your egr might be a culprit ,like is getting unseated .I guess the best thing to do would be to be removed and bench test it by the manual.

 

[Heg87t]

I don't have any vacuum hooked up to the EGR now. I am thinking I need a new IAC since the problem comes and goes and changes at different times. I need to hook my Turbolink back up and see if the IAC counts are still at 20.

I am going to pull the plugs to take a look, change my fuel filter and install my hot wire kit this weekend and see if that changes anything.

 

[pajo]

egr

I guess it does not matter which direction you will go to find the problem ,if you change the iac at least you'l know if that fixed it or not and go from there-good luck and keep us posted what you'l find ..:redface: