Throttle Problem

[BlueHavenKennel]

I recently purchased a 90 model GT Mustang in which we have spent the past two weeks putting back together. Put the engine back in yesterday and it ran fine until later on this evening. But now the throttle hangs on it. Other than that it runs smooth, no surging or anything. It is fuel injected. You can bump the gas pedal to 2 or 3,000 rpms and it will hang there for 30 seconds to a minute before slowing back down to idle. We are thinking that it may be a vacuum leak but have no idea where to start looking. Any suggestions? I am dying to be able to drive this car but not if the throttle is going to hang wide open on me if you know what I mean. LOL. Thanks in advance.

[GhettoPop]

check your TPS (throttle position sensor) located on top on the throttle body. i think its your problem.

http://www.muscularmustangs.com/tps.php

http://www.corral.net/tech/maintenance/idlereset.html

post any questiuons you have a good luck.

[Philossifer]

Originally Posted by BlueHavenKennel

I am dying to be able to drive this car but not if the throttle is going to hang wide open on me if you know what I mean. LOL. Thanks in advance.

BlueHavenKennel,
I had the same problem that was haunting me for over a year since I put a new motor in my car.

After asking every intake question possible and swapping everything from the air filter to the intake plenum.....out of the blue, I decided to try something I hadn't heard of here; or anywhere.

First, I adjusted the idle screw as per my Chiltons service manual. With this setting, the idle would always hang for about 5 or 6 seconds before settling in. Next, I slowly (1/8 turn at a time) turned the screw outward. It seems like it takes a while for things to settle in with EEC-V so I would turn the screw outward 1/8 turn and then drive the car for a few days......

After about five tries, I got the idle to not hang but it had a tendancy to want to stall sometimes. No problem, turned the screw in about 1/8 turn and all is well!

In my case, maybe it was the new cam. Everything else on my engine is basically stock but it would not idle right with the idle screw set to the service manual settings. With the original stock motor, setting the idle the way the manual indicated would always turn out a smooth, steady idle.

If nothing else works, give this a try! Might work for you.
Phil

[randbstar]

Yeah, I agree. I had the same problem when i had to adjust my idling a few days ago. I had it too forward so it would hang for about 5-7 seconds before going down.

disconnect the cable(-negative) let sit for 20 minutes. Then disconnect the IAB which sits in front of throttle body. Connect cable back and turn car on. Start turning to right 1/8 (increase) or turn to left (decrease). Its quicker to have someone in the car to watch the idle. Depending on if you want it alittle advance then turn to right so it is over the 1 RPM.

For myself it was too far forward at 1500 RPM. So i adjusted to it got on the "1". If its under the 1 it might hesitate or cut off. Keep it at 1 or above that.

The only time i had "hang time" was when the EEC was reading the new settings.

Once you find the right setting, turn car off and reconnect the IAB. let run for about 2 minutes with no accessories. turn off again and let sit for 2 minutes. turn back on with all accessories on for two minutes. you should be good to go. then of course, test drive that baby and see what happens.

Oh, also check your TPS make sure it is around .95 - .99. but not more than 1. If so, it may start doing some funky stuff.

Sierra

[BlueHavenKennel]

Hi everyone. We changed the Idle Air Control Valve, which had quit moving and the throttle position sensor checked out fine. We used carb cleaner to check for vacuum leaks per suggestion from my co-workers but didn't find any. So, we just tried turning the idle screw and closing off the butterfly in the throttlebody. And making me feel totally stupid, it slowed down the idle. It wants to idle about 1100-1200 rpm which is still a bit faster than I want but at least its not racing now. Still can't figure out why we had to turn the screw since it wasn't touched when we took the engine out or put it back in. Anyway, this car has a huge throttle body on it. We compared it to the one we took off of my old mustang (an 89 LX with a 5.0) and to one that was given to me off of a 94 with a 5.0 and it is bigger than both of them. Any ideas if that is normal or if not what it came off of? It looks the same, just a larger hole and butterfly. But anyway, she's coming along, slowly but surely. Just replaced passenger side wheel bearings in front so now it's not so mean to drive, and just primered the front bumper. Still have to take a new picture. Hopefully before too much longer we will have her looking more like my old one, only in GT style. LOL.

[randbstar]

I understand where your coming from but if there is a bigger throttle body then the idling will need to be adjusted to compensate, right? Bigger throttle body is allowing more suction so everything has to work together as unison.

Also when a battery is disconnected for a period of time, doesn't the memory clear? If so then the idling will have to be reset because the computer doesnt have the settings anymore.

Not sure why you would close the butterfly to adjust the idling. But again i will start off at 1000 rpm, then drive and see how it feels. From there keep adjusting to your liking.


Anybody else have any thoughts on this?????