Idle with IAC disconnected...

Tech_Greek

Registered User
I'm thinking that the car has a bad leak on the stock IC on the end plates or in between and today I tried the disconnect IAC procedure and it idled (albeit just a little lower) just fine.

So a few questions:

1) Would the car idle if it had a leak like this, moving the bypass valve by hand didn't make it die.
2) Would oil build up in the IC cause an increase in boost - I'm showing 15lb's starting off as soon as I floor it and climbing as the RPMs increase - I don't think it's accurate but not sure, it idles with -20 in P and -15 or so in D...

I can't tell what the PO has done to the motor (the one before last) considering the IC Collar Nut has been tampered with I'd say he's at least gone in there and replaced the HG's but I have no idea if he's done any head work, etc that would cause it to raise...
 
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I don't agree with doing the IAC test to see if the car stalls, and believing that is going to determine vacuum leaks or not. If everything is good, unplugging the IAC should only lower your idle RPM about 150 RPM's or so but not stall the car out. Imagine being somewhere and the IAC fails... I'd at least like to get home ;).

Frit
 
So, it does go up about 100 RPM or so...it idles right around 800 RPM in P and right around 600 RPM in D with the IAC connected (but if I disconnect it in D or P it will go down a little, but not enough to kill it out).

I know I have a boost leak on the end tanks of the intercooler because I sprayed carb cleaner on the actual end tank and the idle smoothed (I say smoothed, I mean raised) when I hit it...
 
So, it does go up about 100 RPM or so...it idles right around 800 RPM in P and right around 600 RPM in D with the IAC connected (but if I disconnect it in D or P it will go down a little, but not enough to kill it out).

I know I have a boost leak on the end tanks of the intercooler because I sprayed carb cleaner on the actual end tank and the idle smoothed (I say smoothed, I mean raised) when I hit it...

If you know you have leak...then fix it before messing with anything else. Doesn't take much of a vacuum leak to make these cars run like crap.

David
 
The car doesn't really run like crap thats the thing - if anything it runs 90% better than it did whenever I first got it (good enough to hang with my Galant that ran a 13.8 all the way up to 95 MPH).

I'm just trying to figure out if I'm wasting my time chasing down a ghost or if I should just proceed and try and work on the rest of the car.
 
fix the vac leak first.my 89 had a vac and ran fine ,found the vac leak,fixed it car ran great.
 
To test with the IAC disconnect you would need to back off the throttle plate stop to ensure it closes all the way. The correct setting should be just above engine dying.

You can have a vac leak that isn't sufficient to have it keep running. Only if the leak is fairly large with the motor keep running.

Fixing vac leaks is simply chasing each one as you find it. If you know the IC is leaking, fix that one, then test again.
 
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