Idle hangs at 1500 after revving.

Hello,

I have a 91 LX with a 347 stroker HCI EFI and I have had the car dyno tuned in the past and had the same issue. I am having a problem where when I rev the rpm gets stuck at 1500 for a few seconds then drops down to normal 800-900 range. I unplugged the IAC and revved it and it does not get stuck. I have tried motorcraft IAC and aftermarket and they both act the same when plugged in. I was thinking of doing the base idle reset but do not know what else would cause this. Please help.

Mustang5L5 said:

Auto or 5-spd? Does the ECU match the trans or is this a 5-spd swap using an auto ECU?

Dump the engine codes. Do not press the clutch pedal in. Do you get a code 67?

Click to expand...

Hey so i was doing the base idle reset and noticed my tps was loose. Performed it and it fixed it but my rpm was too low for the cam in drive (AOD). Adjusted my idle rpm and my TPS went too high I set it to .96 and it started to hang again. I have unplugged the battery just now and will see if that fixes it.

Turns out my idle stop screw was too far in. The more I back it out the less hang it has and it goes away. My issue now is that I have to have IDLE rpm at about 650-700 to have no hang but my cam likes 800-850. I will back it out to about 700 and then advance the timing until I am at 800 or so.