88 GT wandering idle

Most likely cause is a bad idle air bypass valve. You can try cleaning it and when they doesn't help buy a new one for around $70. Easy to install.

----------------- Jim '88 LX 5.0 (now in car heaven) '89 LX 5.0 vert '99 GT 35th Anniversery Edition - Silver Mods to date - Relocated trunk release to drivers side, shortened throttle cable.

Okay, Thanks for the tip. I'm new to mustangs, so i have to ask for a little more help lol Where is that located on the engine? Are aftermarket sources okay for a new one or should i go to ford? Any idea where i can get a factory service manual? Thanks, Justin Webb

I don't know that I've ever seen aftermarket but you could check with AutoZone/Pepboys/etc.

It's a cylinder about 1 inch around and 3 inches long held onto the side of the Throttle body with two bolts. There is also an electrical connector plugged into it. There is a thin gasket between it and the mounting surface that you'll probably need to reuse unless the new one comes with a gasket.

Go to

in the second picture down there is a throttle body for a v6 thathas at the top the IABV bolted to it. The V8 looks similar.----------------- Jim '88 LX 5.0 (now in car heaven) '89 LX 5.0 vert '99 GT 35th Anniversery Edition - Silver Mods to date - Relocated trunk release to drivers side, shortened throttle cable.

Another thing is that the bolts holding it in could be loose as well. This happened to me on my old 4 banger.

Don Manning

that >located on the engine?

If you would like to learn where the components are located on your motor, you can view the TECHNICAL section of my website (see below). I have an engine compartment diagram showing the location of just about all the sensors and major components, please feel free to print it for your use.

Hope this will be helpful

TIM -aka- MUSTTANGUY "at" AOL "dot" COM

Is the idle air bypass valve the same as the IAC? If so i think i found the location. Doesn't seem loose or anything. Thanks, Justin Webb

Yes, they are the same. Another thing you can try before replacing or cleaning it is to adjust the throttle stop. Even after putting a new IAC on my old 88 it would still wander occasionally at idle and hang when coasting. I tried several recommended adjustment procedures and finally made up my own, which seemed to work as it never again had any idle or coast problems.

There is an idle stop screw on the underside of the throttle body, down where the gas pedal cable attaches. WIth the engine off, back that screw out till you can see it's no longer touching the stop. Then turn it back in till it JUST barely touches the stop (actually it's a level that moves, not a stop, the screw is mounted to a fixed mount). After is just barely touches, turn it in an additional quarter turn.

----------------- Jim '88 LX 5.0 (now in car heaven) '89 LX 5.0 vert '99 GT 35th Anniversery Edition - Silver Mods to date - Relocated trunk release to drivers side, shortened throttle cable.