Car Keeps Dying - IAC Valve Bad????

A couple of thoughts come to mind. One is that the IAC dropped a deuce on you. Just gotta get a new one if so.

First: how is your idle set? I've seen some that were set very low and the IAC had a large duty cycle just to maintain a warm idle. Clue: WHen you start the car in the morning, how high are the RPM's initially? And where are they normally (hot engine, no accessories on)?

I like to set the idle with the IAC disconnected. This means that even if the thing took a total dump on me, the car would idle just fine when it's hot and I dont have accessories on. Then if I use AC or have other loads going on, the IAC only has to help out a little. Some folks have their idles set so the IAC is needed always, and if it starts to take a poop on them, the car wont idle period.

My random thoughts. Good luck.

Personally, I think that if your IAC is working, your IAC is probably got some decent duty cycle at hot idle. E.g., I have my hot idle at 700 RPM and my cold (start-up) idle initially is 1400 RPM, then it drops to 1100 after 10 seconds, then down to 900 till it's warm.

If you had a hot motor and disconnected the IAC, the motor would likely die.

To set the idle you can use the idle stop screw or the bleed screw. I only recommend using the stop screw. It's the threaded shank on the TB (where the throttle cable connects). If you tighten it a turn or two, it should bring the natural base idle up a little bit. I like to put a mark on the idle stop screw and write down adjustments - that way you can always go back to how you have it set right now.

I make an adjustment and drive it a day and see how it does in all conditions (and while the puter adapts). I adjust more as needed.

Good luck.

Here's some info with pics. Each page on that link has more info. That's page 3 that's linked to.

Good luck.

I am selling a practically new Ford Racing IAC and TPS if you want them just pm me.

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Sompin2do said:

I need to make sure I'm doing this right. On the link for Resetting The Base Idle, step 2 says "disconnect the plug going to the idle motor". Is that the plug for the IAC or the one on the firewall side of the throttle body? I disconnected the plug going to the throttle body and did the procedure but had to turn the threaded rod several turns before I could get the idle up at all. Now it doesn't seem to stall but is idling too high, and seems to take too long to kick down.

I did have my mechanic drive it all last week because it was starting to bog at about 45mph. He only got it to happen once and couldn't pull any codes.

Click to expand...

Yes, disco' the IAC electrical connector.

It's possible that the Idle bleed screw was previously used to set the idle (that's how the manual tells you to do it, but I think that method leaves a bit to be desired). If the bleed screw is run too far out (for me, more than ~ 1.5 turns), I get a hanging idle (this bleed jet simulates a vac leak).

I'd take copious notes of how things were and what adjustments you make and try to reset the idle till it suits you.

Good luck.