HELP!!-- I have to leave on a road trip tomorrow and I need help with my '89 GTA 350-- my engine RPM run up to 2500+ RPMs all the time- while driving or idle, in drive or park/neutral, etc. The linkage is not stuck-- not sure what the cause is. I have another working TPI system in my garage that I can take parts from. Who can advise which parts to quickly swap out to get this problem fixed in a hurry?? Throttle body? TPS? Thanks for your quick help!

Additional Info:

I get no "check ingine" light. I replaced the MAF sensor, no change. I did notice the following:
1. When the engine is off, the throttle springs all the way back, resting on the adjustable stop (as it should).
2. When the engine is running, the throttle keeps a minimum distance from the stop (about 0.08 inches), givin an idle speed of about 1200 rpm (hot or cold). And if I press on the throttle to get to 2200 rpm (now with a gap of about 0.20") and let go, the throttle stays there and does not spring back, as something is holding it there (until the enginer is turned off).

Any suggestions on what to change next??

 

sounds like you just need to lube up you linkages, or the throttle cable is sticking just a little bit

 

Why would it only "stick" when the engine is running, and seem perfectly fine when the engine is off?

 

Hi Harry,

Can it be moved by hand when the engine is running?
If so, a quick fix might be(turn engine off first) to spray lube around both sides of the shaft, open the butterflys and clean the soot around where the openings(front/and behind) with a rag that has carb cleaner on it; also clean the back side of the butterflys.

Also maybe add a car spring to the hole just under the linkage where the cruise control link up and pull it forward to the mounting bolt on the alternator.
I stretched the spring a bit on mine so it had some tension but not too much.

regards,
Brent

 

I just though of one more thing...

Is it possible that cruise control is pulling it back(malfunctioning)?

If so, maybe just unhook the linkage?

 

I already checked the cruise control. The linkage has a bit of slack in it while this problem is happening-- same with the foot pedal linkage. Something else "inside the throttle" is controlling/affecting the behavior. Even though it seems to "stick" at a certain position, I can push it back towards the stop (getting down to about 1200 rpm), but something is opposing the throttle going all the back-- and then the behavior goes away immediately when the engine is turned off... other suggestions??

 

I had this happen to me a while back, luckily I wasn't about to hit the road for an extended trip. I'd be driving and let off the gas and it'd keep a rollin' on down the road not wanting to stop. I had to blip the throttle to bring it back down.

What had happened was I previously took the throttle body off to clean the gunk out of it, using carb cleaner I believe. The problems happened and I hooked my scanner up check the TPS. It would show a value indicating an open throttle, I'd blip and the TPS went back to it's idle value.

The solution was simple: I lubed (WD40) the shyte out of the throttle body, shaft, butterflies, spring, anything in that area. It worked and blipping stopped.

 

That's sounds exactly what my problem is-- I currently tap ("blip") on the gas pedal to try to get the motor speed to come down (and occasionally shift into neutral to save wear on teh brakes!)-- this works sometimes, but not all the time! I will clean out the throttle body and post a reply... thanks for the comments..

 

Maybe I overstated the cleaning and understated the lubing. What I was saying was your throttle blades are sticking, hit those with some WD40 and you can probably forego the cleaning.

 

Engine vacuum is putting pressure on the throttle shaft when it is running, when you turn off the car there is no vacuum and no throttle shaft pressure. Spray WD40 on the tthrottle body shaft at all bearing positions and the problem will go away.

 

also clean out IAC

 

Sorry for my ignorance-- "IAC" = "idle air control"? Where is this located (relative to the throttle body)? Thanks...

 

it is located on the lower passenger side of the throttle body. There is a tech article on the main page on how to clean and adjust it

 

Can the TPS get damaged by getting to much WD40 on it?

 

Maybe if you saturate the electrical connections, if you're concerned, just take it off and reset it when you put it back on.

 

Well-- I finally solved the problem. I replaced the entire tb (throttle body) and the problem is cured. Before I changed the tb, I did lubricate the moving parts, as per some of your suggestions. While I was doing that, I noticed that the feel of manually moving the tb open and closed was not smooth, and suspected a bad shaft bearing. So I decided to change the tb, and now the idle problem is fixed. Thanks to everyone for your input!...