Sometimes the car dies with a/c on when I step on clutch...

[stang8urimport]

Yeah, so today I put on a GT-40 intake with a ported lower, 70MM t/b... But this all happened before the intake also.

Sometiems with the a/c on... I'll just be cruising... come up to a light or a stop sign, step on the clutch and it will instantly die. Sometimes it's fine... Sometimes it'll go to like 500 RPM then surge just a little bit the smooth out. The IAC is clean as can be... but it's almost like sometimes it forgets to work. Without the a/c on... it's FINE... never does it... When I step on the clutch, it will go to about 1100 RPM like it's supposed to then when I come to a complete stop it will slowly come back down to idle... like it's supposed to. Any ideas?? No stored codes...no CEL... Maybe the IAC is half way to taking a dump??? It is original to the car with 101000 miles... If I turn the idle up and reset the tps, it will do it about 1/4 of the time.. but I don't like the 1000 RPM idle. JR, JT??? You out there? Thanks in advance.

 

[stang8urimport]

ttt?

 

[Grn92LX]

Clean the iac.

 

[stang8urimport]

The IAC is clean as can be...

 

[srothfuss]

How are the grounds..? My car used to die once and a while like that because the ECU wasn't getting enough juice to run the computer.

Upgraded the wiring and that seemed to solve the problem.




I think I remember you did this already, but maybe I was thinking about someone else.

 

[stang8urimport]

How are the grounds..? My car used to die once and a while like that because the ECU wasn't getting enough juice to run the computer.

Upgraded the wiring and that seemed to solve the problem.




I think I remember you did this already, but maybe I was thinking about someone else.

Yep... I Got a 2 gauge battery ground, and a 2 gauge engine to chassis ground. Grounds are awesome. I've heard these Ford IACs take a dump half way before going all the way out.. Maybe I should get a new one?? Just trying to figure out the problem... I'm not a parts changer.

 

[90mustangGT]

That is odd. Hmmmm..... that is really something else. It kind of sounds like something is crossed or something so that when the clutch starter safty switch turns on or the cruise controll clutch switch is opened it interfears with another sensor. Maby the IAC plunger is moving to fast to close and not fast enough to open. When you hit the clutch the computer tells it to idle down, but then closes too much but then when it starts to open again, it cannon open fast enough. It could be a bad motor, the motor reverses polarity to reverse direction, so maby one side has a bad ground or open. This is just a guess.

 

[stang8urimport]

That is odd. Hmmmm..... that is really something else. It kind of sounds like something is crossed or something so that when the clutch starter safty switch turns on or the cruise controll clutch switch is opened it interfears with another sensor. Maby the IAC plunger is moving to fast to close and not fast enough to open. When you hit the clutch the computer tells it to idle down, but then closes too much but then when it starts to open again, it cannon open fast enough. It could be a bad motor, the motor reverses polarity to reverse direction, so maby one side has a bad ground or open. This is just a guess.

There is something to this... Because if I push the clutch pedal ALL the way to the floor, it will idle up a little.. and it I bring my foot just off the floor, the idle will go back down a little... nothing major.. but atleast 100 rpms.. I thought it was sorta odd... IAC causing this?? Does the clutch switch have anything to do with the idleing system? The clutch switch isn't BAD, cause it has never not started because of the clutch switch. ?????? Thanks bud.

 

[stang8urimport]

ttt?

 

[90mustangGT]

There is something to this... Because if I push the clutch pedal ALL the way to the floor, it will idle up a little.. and it I bring my foot just off the floor, the idle will go back down a little... nothing major.. but atleast 100 rpms.. I thought it was sorta odd... IAC causing this?? Does the clutch switch have anything to do with the idleing system? The clutch switch isn't BAD, cause it has never not started because of the clutch switch. ?????? Thanks bud.

That rpm difference may be just the load from the tranny and clutch assembly being released. (we are talking about engine running trans in neutral, right?) 100RPM or so is no big deal.

... wait a minute, just read your original post again and I guess I overlooked one key part... it only does this when the A/C is on. I had this exact issue with a 98 Ford Ranger. If you let off the throttle after the engine had been revved, or when comming to a stop, the A/C would cut off, this being in a newer OBDII vehicle it turns off the compressor if the RPM dips too low, on EEC-IV cars like ours it doesn't have that feature. It also tended to stay at a higher rpm for longer times comming down form a cruise, but then it would finally dip real low. So, anyways, I cleaned the TB and whole induction system, same problem, did the Ford Idle Reset procedure, helped but did not solve. No codes in the computer. Finally, just tried a new IAC and it fixed it. Try a new IAC motor, just don't mess it up so if it isnt' the IAC you can take it back.

 

[super302]

my 90 vert did that crap, i was dumb at the time (still am) so i just never turned on the a/c

I suggest (like 90mustangGt) to try a new IAC

 

[stang8urimport]

Thanks guys. New Motorcraft IAC valve on the way.

 

[TheUser]

since it's an electronic part, I really doubt you'll be able to return it if that's not the problem, but a new one won't hurt regardless.

I was going to suggest just not using the A/C too until I noticed that he's in Florida. Although it does get 90-100 here regularly in the summer and I don't use a/c...not everyone can stand that.

 

[stang8urimport]

since it's an electronic part, I really doubt you'll be able to return it if that's not the problem, but a new one won't hurt regardless.

I was going to suggest just not using the A/C too until I noticed that he's in Florida. Although it does get 90-100 here regularly in the summer and I don't use a/c...not everyone can stand that.

Yep... I refuse not to use the a/c lol... The IAC sounds like the only plausable causes... Wish me luck