I'm on my 3rd IAC valve since I had new motor put in back in April. Motor is a 96-99 vortec 5.7 with GMPP intake and new throttle body. https://ck5.com/forums/threads/91-suburban-slowww-build.321867/page-4#post-3637659 It runs fine for a couple of months, then the idle gets erratic and eventually SES light comes on and I change IAC. Cycle starts again. I only run premium and I put a 195 thermostat in hoping that would help. It didn't. Any help or info would be appreciated. Thanks
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IAC Valve 91 Suburban Trouble
- Thread starter Rmy660r
- Start date
ratfink65
Registered Member
Hey we have the same truck! Mines an 89 with a vortec crate engine and Thorely headers. Execpt mine has an RV Morse bored TBI, Weiand Street Warrior intake and I have an EBL Flash computer.
Does your TBI turn freely? Can you data log? Who did your tune?
Does your TBI turn freely? Can you data log? Who did your tune?
TBi chips hasn't had real good reviews the last few years it seems. I have no personal experience, just what I've seen reported online.
Do you reset your IAC and see if that fixes the problem? The tune isn't going to cause the IAC to fail AFAIK, not sure if you can change the parameters so it was working harder than it should be, but it would seem an unlikely issue.
Do you reset your IAC and see if that fixes the problem? The tune isn't going to cause the IAC to fail AFAIK, not sure if you can change the parameters so it was working harder than it should be, but it would seem an unlikely issue.
black dawg
1/2 ton status
If the base idle (throttle plates) is set too high, the IAC will be constantly be bottomed out against the seat during idle conditions. This is the only thing I have seen cause iac failures. If you could data stream it, set iac counts to between 5-10 fully warmed up and in D.
ratfink65
Registered Member
This is what I was thinking. Your getting a code 35 right?
I know its kinda spendy but EBL is really the way to go. You could also check here http://www.thirdgen.org Lots of info on vortec swap tbi. No love for tbichips over there either.
I know its kinda spendy but EBL is really the way to go. You could also check here http://www.thirdgen.org Lots of info on vortec swap tbi. No love for tbichips over there either.
This is what I was thinking. Your getting a code 35 right?
I do not think TBIchips is in business anymore. Off the shelf chips do not work if there is any deviation from the exact parts it was matched for. EBL firmware is not available for ECMs with a transmission PCM controller (I wish it was or I would buy it for my 7060 ECM). Look for vacuum leaks, remove the idle screw plug on your TBI, then go through the steps of resetting the IAC. If that does not work, then start looking for something more complicated. Don,t start looking for the most complicated problem first.
Thanks for info guys. I knew that TBIChips had bad reviews, but I kinda had no choice. Nobody local to burn chip and that is way beyond my computer skills. No idea what code it was throwing. I changed IAC as soon as it started giving me trouble. I turned my idle way down with the idle screw on tbi, doesn't seem to help.
black dawg
1/2 ton status
base idle has to be adjusted correctly to have decent idle stability and starting. I like to have as much throttle opening as possible, without iac being bottomed out. An old scan tool would give you some good info, as well as using a laptop with the correct cable and downloads.
That's not how you adjust idle. You can google "minimum air adjustment tbi" and probably find the proper method. You still aren't adjusting idle RPM, that is set in the ECM/PCM, however that changes the position of the IAC.
I doubt your idle problem is with the TBIchip. When I said remove idle screw plug from your TBI...that was just a starting point to go through the entire steps needed to adjust your IAC.
