DillonInCO

Searched but couldn't find much info...my car has had this weird issue since I bought it. It didn't really bother me at first, but it seems to be getting worse as the weather gets warmer. Car is a 2000 GT, stock except for a BBK CAI and SCT 93 octane tune (although it did this with the stock tune as well). Description of the kinds of things I'm seeing:

- With the car at a stop, in neutral, rev it to 2500 RPM or so, sticks there and slowly falls down until it idles at the correct spot

- Coming to a stop, put the clutch in to shift, RPM falls but hangs at various spots

- Coming to a stop, put the clutch in, put it in neutral, RPM falls down to idle then revs back up to ~1200, hangs there until car comes to a complete stop, then idles normally

- Sometimes the ABS motor engages below 5 MPH when coming to a stop (probably unrelated, but my thought is that if the car senses throttle and brake at the same time it might do this)

No check engine light and no pending DTCs. I've done some basic checking for vacuum leaks and haven't found anything obvious.

I want to back out the throttle adjustment screw on the TB but it's stuck in place---someone decided it would be a good idea to slather it with loctite, and besides that, I don't see a slot or anything on the screw to use a tool to turn it. (Edit: Appears that maybe this is factory and the screw isn't supposed to be adjusted?) Tried grabbing it and turning it with a pair of pliers but didn't have any luck. What can I do about that?

Also, I hooked up the SF3 to do some data logging, and it showed the throttle position at 20% while sitting still with my foot off the gas. Minimum throttle position throughout the whole drive was 20%. Is that normal?

So...any thoughts on what might cause this? Where should I start troubleshooting?

DillonInCO

Almost 100 views and nothing? I hooked up the SF3 to try and data log voltage from the TPS (using their LiveLink software), but when initializing, it gave me an error that said something like "failed to set up..." and then only logged the items that it could, which didn't include TPS information. Guess I will do a voltage test with a multimeter this weekend. And try to remove the loctite from the TB set screw so that I can adjust that if necessary.

school boy

This is a common problem with these cars. The iac is staying open too long or maybe sticking. First try cleaning it. If that don't help ill post up a link to a iac gasket that has a smaller hole that helps hanging rpms.

school boy

http://www.ebay.com/itm/86-04-FORD-MUSTANG-GT-V6-4-6L-5-0-IAC-RESTRICTOR-GASKET-89-90-91-92-93-95-96-97-/111056979064?_trksid=p2054897.l4275
here you go

school boy

double post

DillonInCO

Awesome, thank you! Strange that I couldn't find that by searching. Guess I wasn't searching for the right thing. I'll try cleaning it ASAP.

Edit: Read a bunch of stuff that said that cleaning won't help, or rather that it's a band-aid fix at best, and that I probably need a new IAC. I'll post back later with the results from cleaning.

needmorespeed

Just came across the thread. I have had a similar issue with the rpm's hanging, seemed to be a mostly summer thing but found this video and thought the motor looked a little too familiar

Lackey'sGT

Has anyone used this and have you guys had any problems with it?

DillonInCO

Cleaned the IAC, didn't make one bit of difference (but it honestly wasn't that dirty to begin with---looks like it may have been replaced at one point already). I'm thinking it is probably the TPS, as I still don't get why the ECU would be reading 20% throttle at idle. Is the TPS position adjustable? I know on a lot of cars you can loosen the TPS and turn it to adjust idle.

Burtonsnow157

i had a similar problem to what you have. i would let off the gas and the car would stay at around 2500 rpms and drive itself like it was in cruise control and the gas pedal was sticking. this only started to happen AFTER i did preventative cleaning of the iac and throttle body so i was super annoyed but my fix was the throttle body adjustment screw - it was letting the butterfly valve/blade close almost all the way which caused vacuum lock. i turned the screw to open it up and raise idle a little bit and that solved the problem. i know you said your screw is stuck. . . is it stock or aftermarket