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Silly question, but what does IAC stand for
- Thread starter gundog
- Start date
lilredwagn
NAXJA Forum User
- Location
- South Carolina
Idle Air Controller motor. It opens the butterfly on the throttle body to adjust idle speed.
bajacalal
NAXJA Forum User
- Location
- San Diego (North County), California
It doesn't really open the butterfly though (although some carb applications had a system like this) it pushes a metal cone (plunger) into a mated seat (hole) regulating the flow of air (controlling idle speed).
devildog0
NAXJA Forum User
- Location
- Hunt County Texas
bajacalal said:
X2
afd516
NAXJA Forum User
- Location
- Fort Worth, Tx
Since we are talking about abreviations, what about IIRC? I think thats what I keep seeing.
Lou
NAXJA Forum User
- Location
- ToronNo/Hamilton
red91
NAXJA Forum User
- Location
- exact location unknown
Lou said:
learning is highly overrated. IIRC...
jeepsrock
NAXJA Forum User
- Location
- LA California
Other than having extremely too low or too high idle can the IAC cause a unstable idle.
pete
pete
outlander
NAXJA Forum User
- Location
- Columbus,Ohio
yes......
jeepsrock
NAXJA Forum User
- Location
- LA California
So would it be better to disconnect it after it has started and warmed up or before start ?
pete
pete
AJPulley
NAXJA Forum User
- Location
- South-eastern MA
If I'm not mistaken, at least for the Renix computers, when you unplug IAC when engine if off, then start engine, IAC will not respoond to ECM's comand to open then ramp down (idle raises then lowers quickly). If the engine is in good shape, it should start OK and just idle low, depending on what the stop screw it adjusted to. Mine does at least. Maybe the post-90 4.0s are a bit different. I had a wierd idle issue that took me two years to figure out- turned out to be a throtlebody issue. I doubt its a common thing.
Cherokeelaredo
NAXJA Forum User
- Location
- Aurora, Canada
ajpulley said:
Can you please specify,I am experiencing some idle issues on my 89 4.0.
Low, erratic, etc.
thanks.
outlander
NAXJA Forum User
- Location
- Columbus,Ohio
Welcome to the club,I'm having issues with my 89 also.I found a crack in my exhaust manifold and I'll be putting a new one on to see if it helps...but I'll also be replacing all the sensors also just to make sure.
AJPulley
NAXJA Forum User
- Location
- South-eastern MA
Yup, maybe it might help you, or someone. I had a real weird idle issue that I finally figured it was more pronounced when engine was warm, and after cleaning the intake (usually once a year). I would check everything, and assumed it to be the IAC motor. Guess what...Cherokeelaredo said:
It was the throtle plate inside the TB. When the engine was warm (hot really) the TB would expand just enough to cause the plate to hang up, but only the smallest bit so I could never feel it in the pedel, and it was speratic at that. So, I loosened the two screws that hold it in place and carefully adjusted it to sit perfectly in the bored opening. No more idle issues. I also have backed the stop screw about 1/2 to 1/3 of a turn. Idle is now about 700-725 (600 without the IAC hooked up for testing).
Re: disconnect, warm it up and wait till it happens to be idleing at a reasonable speed then disconnect and it should stay there. If you do that it will need manual help from your right foot to get started and idle when cold. If the idle is still erratic with it disconnected then you have some other problem. BTW check your codes first.
