Aod To T5 Swap Complete Hanging Idle

[theYman]

I have recently completed a T5 swap and now am fighting a hanging idle issue. I am using the stock A9p AOD computer. I have all 3 clutch switches connected with factory plugs. Could this be the problem?
The car starts well and idles at 800rpm then after driving coming to a stop the idle hangs at 1200 rpm. If I kill the motor and immediately restart it idles back at 800. Thanks for the help.

 

[stang89bidges]

That actually sounds more like a TPS module or vacume issue. Something along those lines. Have you ran codes yet?

 

[jrichker]

You guys with idle/stall problems could save a lot of time chasing your tails if you would go through the Surging Idle Checklist. Over 50 different people contributed information to it. The first two posts have all the fixes, and steps through the how to find and fix your idle problems without spending a lot of time and money. It includes how to dump the computer codes quickly and simply as one of the first steps. I continue to update it as more people post fixes or ask questions. You can post questions to that sticky and have your name and idle problem recognized. The guys with original problems and fixes get their posts added to the main fix.

It's free, I don't get anything for the use of it except knowing I helped a fellow Mustang enthusiast with his car. At last check, it had more than 159,000 hits, which indicates it does help fix idle problems quickly and inexpensively.

 

[theYman]

I did not do an idle reset since the swap so I will start with that. Should I connect the clutch switch for NSS, leave it open, or connect it with a fuse?
Thanks

 

[jrichker]

Do the checklist first, then after you have found and fixed any problems, do an idle reset. You may have other problems that are causing your idle to hang.


Edited to correct error.

 

[theYman]

I have read that with the stock aod computer, no modifications to the O2 harness are needed. Please explain.

 

[jrichker]

I have read that with the stock aod computer, no modifications to the O2 harness are needed. Please explain.

You are correct, A9P and auto trans O2 sensor harness work together with no problems. I missed that when I read your original post.

 

[squeak93]

Work the Hanging idle checklist, none of the clutch switches have anything to do with Idle. (only starting car etc).

 

[theYman]

I would agree with you except when I push the clutch in with the switches connected, the idle changes about 200 rpm.
I believe the AOD computer is seeing this as if the auto trans selector is put into gear, thus rising the idle to compensate.

 

[Mustang5L5]

I would agree with you except when I push the clutch in with the switches connected, the idle changes about 200 rpm.
I believe the AOD computer is seeing this as if the auto trans selector is put into gear, thus rising the idle to compensate.

WHat year Mustang do you have?


The Computer does do this, but it gets it's signal from the VSS on the transmission. SO let me ask this. Did you install the VSS when you converted to the 5-spd? IS the harness hooked up?

Have you run the codes, because this would generate a code if this is the case.


Connect the plugs to the clutch pedal and forget about them. Not the issue there.

 

[theYman]

It is a 93 GT and I do have a VSS connected. My speedometer is off by 5 mph. Maybe the VSS is bad? I wil check codes as well.

 

[theYman]

Well I did an idle reset. Started up, idled perfect at 800, When I'm driving and stop for a stop sign, it idles back down to 800 at about 5 mph but then races back up to 1300 and bounces around. I ran codes with my scanner and I have to hold clutch in or I get a code 67 ( to be expected I think) key on engine off I get an 11. engine on I get a code 44. All the emission including air pump are intact. I also removed the IAC and cleaned and checked the throttle blade for sludge, none. Interesting thing is even with the IAC unplugged it still surges.

 

[theYman]

I did one more idle reset and this time it seems to be better,