[casino777]

My fiancee recently bought a 1999 V6 with 109k on it.

Yesterday she says the AC stopped working (it was very hot outside if it matters 94 with a 105 heat index very high humidity), just suddenly stopped blowing cold air. So she tuirned it off and on a few different times and finally it started working again. Seems to work fine now, but does anyone have an idea of why that would have happened and is it a sign that something is about to go out?

Secondly, the car has a strange idling problem. It revs very high when you first start it, which doesn't seem all that abnormal to me, (my fox does the same for a few seconds) except it takes a very long time for the idle to go down, and no matter how long you let it sit, it will never go down unless you begin to drive it, and then it takes several minutes. ALso, she says at times, the idle will begin to surge up and down. We brought it back to the dealer she got it from and all they did was replace an idler pulley, but that has not solved anything...and I get the feeling they are not telling her everything. (At the time she took it back it was still under a 30 day bumper to bumper warranty, which is now expired, and only has a drivetrain warranty for a few more weeks) THoughts on what is causing this?

 

[davidcseifert]

To the A/C: have you checked to make sure the freon is fully charged?

The idle: it could possibly be the IAC (idle air control) going bad, does it idle rough or does it just have constantly changing rpm's?

 

[casino777]

DId not check freon. Assumed if freon charge was gone it would just stop blowing cold all together. Just got done driving it and AC is working fine again today.

The idle starts out around 1500 and stays there until the car has been driven for at least 2 minutes. If it stayed in prk for 1/2 an hour, the rpms would never come down until you started driving it. I have never experienced the surging up and down thing that she told me about, I dont drive the car much and it only happens intermittently. But no, the car does not have a rough idle, just the surging and lengthy high idle when started.

 

[davidcseifert]

Just something random that migh be the culprit, check the throttle body and see if it has a name on top, like maybe bbk or acufab, I remember back when I put the bigger tb on my car it idled pretty high for a while until I had the tune adjusted

Other than that I honestly can't think of a way that the idle could be high then get lower later, if it stayed high I would say make sure the throttle cable is not being caught up

 

[wmburns]

It's normal for the idle to be high right after start up. However, it should drop steadly down within 15-60 seconds depending on outside temperature. The colder it is, the longer the idle will be high.

So first confirm that the IAT and engine cooling temperature sensor is returning reasonable values. Why? Because the PCM makes adjustments based upon the temperature that it "thinks" it is.

There are several possible causes for a surging idle. TPS, binding throttle linkage, lose/worn throttle linkage, weak throttle return spring, low on freon, vacuum leak, bad PCV valve.

For more information, check out:
http://www.allfordmustangs.com/foru...-dieing-idle-idling-rough-14.html#post2260649