Irradic Idle
 

I own an 86 GT 5.0 HO, 5spd.

The idle varies between 500-1100rpm--sometimes it holds relatively consistent, and other times it will surge between 700-1000rpm. Please Help

Clean out the idle air bypass valve, the ports it attaches to, and the throttle body & throttle valve (butterfly) with some good quality throttle body & air intake cleaner (STP makes some good stuff). Don't use regular carb cleaner. You might find a toothbrush a big help, especially if this is the first time you've done it. After that, check TPS voltage. You should have a consistent voltage of about 0.80-0.95V, without any variation or wavering, between the center wire on the harness and ground. You have a speed density EFI system, so resetting the computer and idle speed shouldn't be necessary as on later MAF systems. When's the last time you did a complete tune-up? This includes plugs, cap, rotor, wires, and possibly coil (TFI coils are so cheap, I replace mine if there's any doubt). If you want to, you may wanna have the ignition module checked by an auto parts store, just to be sure. Check your ignition timing while you're at it, too.

Okay, yeah, I'm a little obsessive about this, but I like my 'Stang to run well. http://www.mustangworks.com/msgboard/smile.gif

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Capri306, Moderator, The Mustang Works Online
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After doing those very good suggestions, perform a self test in both KOEO and KOER modes and jot down any codes that come up. This will help isolate any equipment that is past it's prime and in need of replacement.

Take care,
-Chris

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Retired Moderator
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all I did to fix my idle problem is disconnect the IAB for 5 minutes and then plug it back in, its worked fine!

Thanks,
Abe

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1990 Mustang GT Convertible, Blue with Grey ground effects and white top. Black Leather interior pw,pl,ps,pm, premium sound system. All stock =(

Thanks for the help....where is the IAB?

I just bought this car two weeks ago and I'm not very experienced with EFI. The car had a complete tune-up before I bought it--new plugs, cap, rotor, wires, exhaust, etc,etc.

abesmith69--Did you unplug it while it was running?

Thanks