Need Help, IAC issues?

[Murdock]

So in park the IAC #'s will count down to 00, but at different times when I go into D with foot on brake they will go to 175 range and AR is about a 6-7, and the car will stay idling. I then shut of the car and do it again and in drive the IAC will count down to 00 and will not stay idling unless I apply a little fuel via the peddle. Only differ between the two is I turned the car off and back on again.

This has been an IAC issue I have been tryng to solve for a few weeks. I did try a new IAC. Seached for Vac leaks.

I do hear a Pssssssss sound for a very seconds coming from under the dash and behind the AC control area. this happens if I build about 10+ boost and let off. Then I hear the Pssss sound for a sec or two and then it stops or it keeps doing it but I just cannot hear it anymore. Could a loose Vac line to the AC be causing me this trouble? I assume any loose vac line would be trouble but could it explain the wild IAC behavior after each start up?

 

[wb's87]

Any bad vacuum lines to these cars can cause problems. Fix the problem with the vacuum line to the AC and see if it helps.


Sent from my iPhone using Tapatalk

 

[Scott Atk]

Dave, Probably two separate issues. Second thing sounds like a bad check valve. I believe it's the one on the firewall. I've had pretty good luck getting IAC's in the past, stop by today if you want. I plan on being in the garage most of the day.

 

[Murdock]

Thanks guys for the info

Scott- Sounds good, I would love to see what you have been working on anyway!! See ya in alittle while.

 

[Murdock]

Ok, so wasn't able to swing by to get some help this past Sunday but did manage to look into it some more. I have a strong 15-16 reading on vac. So perhaps not a vac leak but more an IAC issue? The IAC I used was a brand new older stock AC/Delco. I know new stuff comes bad sometimes... I think I will need a known good one to swap out. I used started fluid and put a mist around all my vac lines and intake, intake to heads and valley pan area, tb connection etc etc.

The thing that is throwing me off is: why does the car act normal on first start up, stays at idle and acts normal, then I turn it off, restart and it shoots up to the 1500 rpm range and stays there. And of course my fuel economy seems to be out the window. Could there be some internal issues that Im not seeing or thinking about?

 

[mikestertwo]

Maybe a worn throttle shaft? What is the TPS voltage when it is idling normal vs. when you have the high idle?

 

[Murdock]

at idle I'm at 38, I will have to confirm the high idle reading. I will see if I can get that tonight

 

[Murdock]

Well I was getting ready to remove the plenum and upper intake to replace the gaskets and get a better look when I came across the back plate of my turbo. A couple of the bolts that secure the back plate where loose. I tighten them up but was wondering if that could be a cause of the high idle? I would start it up but I have it out of commission in order to swap out my trans and convertor and replace my fuel regulator, and a couple other upgrades.

I ask this about the back plate because if that could not be the cause then I need to keep looking or stop tearing about the intake. What do you guys think?

 

[Murdock]

Well I was getting ready to remove the plenum and upper intake to replace the gaskets and get a better look when I came across the back plate of my turbo. A couple of the bolts that secure the back plate where loose. I tighten them up but was wondering if that could be a cause of the high idle? I would start it up but I have it out of commission in order to swap out my trans and convertor and replace my fuel regulator, and a couple other upgrades.

I ask this about the back plate because if that could not be the cause then I need to keep looking or stop tearing about the intake. What do you guys think?

Problem solved.