IAC issues.... never-ending

[SonomaGTlover]

After reading numberous posts about how to set the IAC, things just aren't working for me.

I have had this issue all year nad it just won't go away. Maybe some of you more experienced TUNER GUYS will have suggestions that I could check in TunerPro.

When I start my truck, I usually see rpm's at 1700 or so, not good but if I let it sit and idle for a minute or two it will work it's way down to normal around 800. Turn the truck off and start it up (after driving a distanec) and I see 1700 again. Just today while I was driving it, I noticed that instead of eventually going down, the rpm's increased. By the time I got where I was going the idle was 2300.

I pulled the iac, adjusted it in by hand and made sure it was clean and the spring positioned correctly. Fire it up and it adjusted itself to a normal idle from very low. This tells me that it is working but there may be some issues elsewhere, possibly in the tune I have loaded? Next time starting the truck, I see higher than normal idle again.

Any suggestions on what may be causing this? I don't have any vacuum leaks that I know of and the vac/boost gauge seems to act normal within typical ranges.

 

[vortecfiero]

Re: IAC issues.... never-ending

when i had the same problem I found that my throttlebody wasnt
completley closed. Some crud was causing it to bind and too much
air was getting past the throttle blades.

 

[SonomaGTlover]

Re: IAC issues.... never-ending

Thanks for the post... While I was snooping around before work I noticed this too. My TB does not close all the way. The gap is ever so slight but none the less there is a gap for air to get past. I haven't had a chance to adjust it yet but it's comforting to know that it is a likely source for my problem.

 

[SBNova]

Re: IAC issues.... never-ending

Not that the commanded IAC position is the actual IAC position, but what step is the IAC at when your idle is too high? If its commanding a lower idle but attempting to close the IAC, then your problem might be mechanical. If the steps are high, then its commanding the idle to be high and you may be able to figure out why, and change it.

 

[turbodig]

Re: IAC issues.... never-ending

I pulled the iac, adjusted it in by hand and made sure it was clean and the spring positioned correctly. Fire it up and it adjusted itself to a normal idle from very low. This tells me that it is working but there may be some issues elsewhere, possibly in the tune I have loaded? Next time starting the truck, I see higher than normal idle again.

Did you reset the ECM (pull the ECM-B fuse) after cleaning?

They remember startup IAC position.

What's your MAP at startup/idle... that will be a clue...

 

[SonomaGTlover]

Re: IAC issues.... never-ending

Well, I started witht he simple things since I didn't have imediate access to my laptop.

I removed the IAC and once again adjusted it by hand making sure everything looked good.
I took a look at the TB and adjusted it to where it was completely closed then 1/8 turn clockwise (just for tension)
I fired it up and waited for it to adjust it'self to the desired RPM of 800 then shut it off
I pulled the ECM B fuse and replaced it. FIred it up and idle was much better at 1200
I waited for the idle to settle again and repeated the ECM B fuse treatment
Finally I fired it up again and BINGO... seems to be perfect idle now. Time will tell

Thanks for all the suggestions guys, I'll get the laptop plugged in this weekend to check it out but I think this has solved the problem.

 

[Loeryder]

Re: IAC issues.... never-ending

what procedure did you use to adjust it by hand?

and how the hell are you getting it on and off the TB without removing the whole unit?

I have my Ty idling great with the brown wire disconnected.
but when we plug it in it just wants to die immediately.
Looking into the IAC and TB blades closing now.

 

[SonomaGTlover]

Re: IAC issues.... never-ending

There is just enough room to work a pair of chanel locks in there. (EGR delete) I hate to use pliers when wrenching but it sure saved tons of time in this case. Adjusting them close for a tight grip and the fact that it's such a large size makes it practical.

Jas... you can call me later between now and 6:45 if you have any questions. 530-7813 I'll try to help.

Basically the procedure I used was to compress the spring and screw it in by hand to about 1/2" clearance for the spring. Release the spring and adjust accordingly to be sure the spring is positioned correctly in the slot.

This usually, but not always, yielded an RPM too low so I had to work the throttle until it caught up to keep it running. I've done it so many times that I can tell just about where it needs to be by looking. HOPEFULLY I won't ever have to see mine again.