Thread: Need help with my 90 Tbird

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My other post on this disappeared so here it is again.
My engine is running a high idle after acceleration. If I don't touch the pedal it idles fine. But if I rev the engine it doesn't come back down. The return linkage for the throttle is on the spring is fine I have checked all that. When driving the car will go about 40mph without my foot on the pedal, at stop signs it sounds like I am trying to do a break stand with it.
Is there a vaccuumm that is suppose to bring it back down or something else that might have gone out on it? I only work on carb motors so I am lost on this.
Thanks for any help.

Hey Tim, Let me first say that I don't know my rear from a hole in the ground when it comes to engines. So this probably won't help you a bit ha ha! But, I just went through a very similar issue with my TransAm...pedals not stickin...but the car is revvin and racin down the street doin 35 an accelerating with no help from me whatsoever...I also had issues with stalling and what appeared to be some kind of short (lights flashing etc.) I don't know how it all works together, but turns out I had a bad alternator...once that wuz replaced ...she runs like a dream....

OK, yeah, now that I think about it...I can't believe I actually wrote that post to an experienced engine person LOL...to quote the Grinch "I'm an Idiot....echo echo echo...You're an Idiot...echo echo echo"...Good luck anyway!

OK, assuming that your motor is the plenum-style 5.0, im going to go with this. The idle is mostly controlled by the air intake past the throttle plates. As it seems to increase upon heating, my guess would be that either your plates are sticking due to improper oiling(pcv does a good job at this) or there is something either scoured or caught on your plates. Also, check for vacum leaks on the rear of the plenum. Give more info(motor, turbo?, ect) and we can help more.

3.8 V6 stock engine.
Someone had mentioned to me that there was a motor or something that controls the idle, Does anyone know what this is?
ANd Jerilynne, don't worry about it, If I was that experienced with the FI and EFI engines I wouldn't have asked the question. A carbed motor I can figure my way around and fix, but am lost with this and any help is appreciated.

Originally posted by joker51
3.8 V6 stock engine.
Someone had mentioned to me that there was a motor or something that controls the idle, Does anyone know what this is?
ANd Jerilynne, don't worry about it, If I was that experienced with the FI and EFI engines I wouldn't have asked the question. A carbed motor I can figure my way around and fix, but am lost with this and any help is appreciated.

Well, if ur better with carbed motors, why not drop in a carbed 5.0 and be done with it? . The only thing I can think of is sticky pedal. My brothers 1990 Ranger 2.8 V6 did this, it had some kind of gaurd for the throttle linkage and the cable got all gunked up and it would stick but if you let it set a day or just a while, it would go back, fixed it with degreaser and a rag, just a thought.

Not a sticky pedal, I can play with the linkage under the hood and it snaps back just fine. Thats what confuses me so much on this. I was wondering if there is an idle motor or sensor or vaccumm that controls it that could be screwed up.

You were asking about sensors...i'm sure you already tried this...but I did a Google search for "high idling" on the 90 t bird...came up with a few articles that talked about something called a Mass Air Flow Sensor ---- but the symptoms it described seemed more geared toward lower idling...sputtering etc. & only way to fix it is to replace the sensor....

But also came up with a number of articles and service bulletins from Ford about the "Throttle Air Bypass Valves"...sypmtoms included High or Low idling...

Thanks JeriLynne I appreciate the help and the effort it took you to look those up for me

I'm like you Tim. I don't work on modern engines.
I think Jerilynne is on the right track. The idle is controlled by a computer. The sensors tell the computer what's going on. A bad sensor will give the computer the wrong input. The MAF sensor is the one that goes bad more often but there are other sensors on the exhaust manifolds and catalytic convertor too. I think a MAF sensor costs less than having a technition ( remember when they were called mechanics?) hook it up to a diagnostic computer. Or it might just need a new air filter.

hey check the IAC valve Idle air control valve....it may be bad or gunked up