Idle Problems on warm motor in Park

[91StangGT5.0]

I've noticed that my mustang has been acting kind of strange when it has been driven and then put into park. The idle is fluctuating from ~600(700)rpms-1000rpms and it does it slowly. I have the slightest clue as to what is the culprit to this issue is. IAC? TPS? Other? Thanks!

 

[84Ttop]

I would try cleaning the IAC first, then go from there. you may also want to consider looking for a small vacuum leak.

 

[91StangGT5.0]

I would try cleaning the IAC first, then go from there. you may also want to consider looking for a small vacuum leak.

How do I go about cleaning the IAC? I also haven't the slightest clue on how to find or check for vacuum leaks.....probably the only thing I can't do correctly for some reason...sad I know

 

[84Ttop]

The IAC unbolts w/ 2 bolts check it for carbon build up, they make a special cleaner for it, but i've always just flushed them out w/ some brake cleen. As far as a vacuum leak, check all your hoses and plastic lines for anything visable first.

 

[91StangGT5.0]

There looks to be a gasket in there. Would I need to replace this or will it be good to reuse?

 

[84Ttop]

if it comes apart cleanly, you can re use them, i have, if it tears, you will need to replace it, only a few dollars at the parts house

 

[HISSIN50]

Does it only wander while in park on a hot motor?

 

[91StangGT5.0]

Does it only wander while in park on a hot motor?

Yes it does....it's annoying as hell.

 

[HISSIN50]

Pull codes, just in case it set a soft one.

How high is your in-drive idle? 700 or so?

If you get it to start wandering while in park, you could try unplugging the electrical connector to the IAC and see if it stops. If so, chances are the IAC or EEC (commanding the IAC) are doing it. If it makes no difference, then the IAC is probably not the cause.

 

[91StangGT5.0]

Pull codes, just in case it set a soft one.

How high is your in-drive idle? 700 or so?

If you get it to start wandering while in park, you could try unplugging the electrical connector to the IAC and see if it stops. If so, chances are the IAC or EEC (commanding the IAC) are doing it. If it makes no difference, then the IAC is probably not the cause.

middle of 500 and 1000 rpms...so I guess 700-750rpms? Where should I be idling with a Trickflow Stage 1 Cam, etc?

 

[HISSIN50]

middle of 500 and 1000 rpms...so I guess 700-750rpms? Where should I be idling with a Trickflow Stage 1 Cam, etc?

Depends upon the mods and how the idle was set. 750 RPM would be slightly higher than stock in Drive.

 

[91StangGT5.0]

Here is a video of the problem. It doesn't seem to be the worse of what it usually is....(Go figure when I record huh?). This is what I'm doing in the video....I let it warm up and sit at idle with it in never leaving park, unplugged the IAC, then watched idle, then replugged, watched idle, then put from Park to D, watched idle from gear change, then from D to Reverse, watched Idle change, then changed from reverse to park, watched idle change, revved the engine a little, watched idle, then shut off.

It did not change idle immediately when I unplugged the IAC. I do notice my idle takes a dip when going from one load gear to another...i.e. Drive to Reverse and vice versa. I've had it die on me once if it didn't let it idle for long enough. If I get right in and go from park, reverse, then to drive like from backing from a driveway and drive forward, it would either almost die or die. When I put my shifter in Neutral it idles higher around 1200 rpms most of the time.

ALSO: The ticking noise is an header gasket leak.....stupid bolts on drivers side came loose somehow and blew some of the gasket enough to make a tick. This started yesterday and just waiting on damn backordered gaskets for my headers and ARP Bolts.

http://s298.photobucket.com/albums/mm241/mbonifield04/?action=view&current=MOV00738.flv

 

[91StangGT5.0]

I'll run codes on Wednesday when my Digital Code Reader for my mustang comes in. (Yes, they make code readers for 86-93 Mustangs).

 

[HISSIN50]

At least during parts of it, it sounds like a vac leak issue to me if the cam isn't outrageous (i've never run a TF cam).

A header leak could be screwing with the O2 readings on one side.

Is this a MAF car? Is the MAF clean?

Codes and vac leak checks are where I'd start. FWIW, you can pull codes with a safety pin (though the LCD reader makes it easier).