Trying to get IAC set right

W

WH1_T-Type

Well-Known Member
Joined
Jun 1, 2009
So I spent a few hours trying to get my IAC and TPS to play nice with each other, but no dice. I did do the procedure straight from gnttype.org for setting the IAC. I got it in the range a few times but it slowly drops to zero and stays there. I then took some O2 safe carb cleaner and sprayed the vacuum hoses to see if I have a vacuum leak that is letting in unmetered air. No change in idle. I understand this isn't an exact method..but it is the only one I know. All hoses appear snug on their connections and no obvious leaks. I think I MIGHT hear a hiss coming from the passenger side..but can't tell for sure.
Had the IAC open enough to where it was 175 and idle was around 750-800, but that isn't where it was supposed to be and that is why I started this, plus anytime the idle dropped below 800 the car sounded like it wanted to stall..and WOULD stall when cold.

Car has a turbo tweak chip. Scanmaster. 009 injectors. Line off pressure is 43psi, line on 38psi. Walbro pump from 2 years ago, with less then 2500 miles on it. Stock intercooler, 3.5 lt1 MAF w/GEN II (verified settings per manual)
Here are my scanmaster numbers:

(AT WARM IDLE)
O2 jumping from hight 100's to 400's
AF 07ish
L8 34
INT 128
BLM 125
CLT 190
ATS 80
r 1070
TPS .44 (4.3 at WOT)
IAC 00
cc jumpng from low double digits to mid 200's

Side note: on a suggestion from search results moved the screw for the IAC out to a thread and a half exposed on the other side and the BLM's dropped to 119 and the IAC still wasn't in range.
 
Back the screw out some more and let the throttle blade close a wee bit more and see if the IAC still backs all the way down. I set my IAC to any single digit number. What is your target?
 
it's been backed out to no threads showing now. Was done about a 1/4 turn at a time. Still won't stay above 0. Goal is 10-40....or maybe just a number that stays and not 175, dangit!! lol
 
Pull off your uppipe and see if there is any crud around your throttle blade. Clean it off. If the blade isn't being held open then you have a vacuum leak somewhere. I had a vacuum leak round the doghouse. I had to get a new gasket. It was hard to find that one due to where the leak was....dang near underneath the coilpack/ignition module.

And then there was that time that I had my cruise control cable to tight and it was holding my throttle barely open.
 
OK, will do tomorrow. Is there a better at home method to use for looking for vacuum leaks? How did you find yours?
 
I use one of those hand held propane/butane gas torches and blow it all over the vacuum areas until I hear the idle change. Make sure all your sparkplug wires are on tight.:)
 
I spray around the intake with brake clean until I hear an idle change. Nasty Wendy's method should also work I've never tried it though.

,Dan
 
I had the same problem on Sunday but I also had high blm around 142 and the iac would start at 15 or so and slowly drop to 00. I had put a RJC PVC in several weeks ago and didn't bother checking the blm until Sunday. I read some old posts and decided to change my PVC valve back to factory to see if it would help. I could not find the valve I took out so used the one from my 84 T which is not the correct one and the numbers went to 133 blm and 13 on the iac after driving for about 10 min. Maybe this will help a little.
 
Nasty Wendy said:
I use one of those hand held propane/butane gas torches and blow it all over the vacuum areas until I hear the idle change. Make sure all your sparkplug wires are on tight.:)
Click to expand...

I honestly don't know if this one is a joke or not...it sounds dangerous to put an open flame to my engine....but I do suspect that you are serious and I just need to be careful...please enlighten....lol
 
Hey Matt, you dont light the torch, you use the propane to check for vacum leaks, going around everything, if there's a leak your idle will change from it sucking in the propane.
 
WH1_T-Type said:
I honestly don't know if this one is a joke or not...it sounds dangerous to put an open flame to my engine....but I do suspect that you are serious and I just need to be careful...please enlighten....lol
Click to expand...

Don't light it!!!! Let the propane blow around the vacuum areas and if there is a leak it will change the idle. Yes I'm serious.
 
I just went through this about two weeks ago with a friend & fellow board members car. His idle was high (1000-1100) & the IAC would drop to 0 in a matter of seconds after starting the car. We messed with it for about a 1/2 hr, couldn't get the IAC values to hold anywhere without falling to 0 & the idle would race as high as 1700 at times:eek: Finally he says to me, "I did buy a new IAC motor/valve & brought it with me"

So.... we put in the new IAC motor/valve & bingo!!! all was good. Within 10 minutes we had the IAC holding steady in the 20-25 range & TPS at .44 hot idle

My vote is the IAC motor/valve is shot.:wink:
 
I just had the same problem with 175 IAC reading. I took the IAC out and sprayed it with carb cleaner and made sure the seat was clean where it screws in. Re-installed, set my TPS to .44 and started the engine. It idles below 50 now, which was my target. If that does not fix it, and your TPS is set at .44, and you have the screw completely backed off the throttle lever then I would say the IAC is bad. Just my opinion. These cars are a pain sometimes.
 
Thanks for all the input so far. Ended up staying at work a LOT longer then expected today (typing this from work)...dang surface Navy keeps causing issues for us submariners! lol

Hope to get to try more tonight..

Don't light torch..check. :D

I have a new IAC actually. Bought it a few months back on a whim. I will pull the uppipe and the IAC motor itself.
 
Nobody has said check your throttle body seals....so check them too. They are at either side of the shaft. TPS on on right,throttle lever on left. May just as well remove throttle body disassemble and clean it up. make your own gaskets from auto parts store bulk roll.
 
Agree..how would I adjust the TPS when the key is off? Can't read the scanmaster with no power....or am I missing the point?
 
LOL a 12 hour day must have made me stupid! I meant to say it goes up.01 with the car started.
 
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