V-6 engine races up to 5500 RPMS

[Crashdocs]

I just picked up this 87 Fiero SE form the scrap yard last week knowing the engine wasn't siezed up (but not running) and only one previous owner. All I have been able to find out wrong is the fuel pump was bad. I've since changed it and got the engine running. Well sorta. Engine cranks over and immediately races up the RPMS and stops about 5500 and stays. A few times it dropped down to 4000 but rose again. I figured maybe the IAC valve was bad but replacing it didn't change anything.... Throttle body looks ok and cable moves freely and closes off ...... I'm overlooking something
Does anyone have any idea what's causing this problem????

Jason

[Ragtop_Renegade]

The problem lies in the electronics. It could be the MAP or TPS, but it almost sounds as if the ECU itself has gone bananas.

[Crashdocs]

Thanks for the help, just replaced the MAP sensor and the TPS. Still racing but atleast it sounds better thinking maybe a vaccum leak somewhere..... was told it's mechanical and not the computer.... Lets see, I really don't want to take the 3 pc intake off the engine. Running out of ideas

Jason

Originally Posted by Ragtop_Renegade

The problem lies in the electronics. It could be the MAP or TPS, but it almost sounds as if the ECU itself has gone bananas.

[Ragtop_Renegade]

Wow, that'd have to a real nasty vacuum leak to cause that much rpm increase. Try plugging off the power brake booster line at the intake manifold. If that proves to lower idle back to where it belongs, there is a hole in your power booster line - it runs from the engine to the booster inside the front compartment. I can't think of any other vacuum line big enough to cause that drastic of an rpm change. If that doesn't help, I still think a look at the ecu is in order.

[Crashdocs]

Thanks, I'll take a look at that booster line this weekend instead of mowing the lawn and all the outdoor house work on a long weekend :O)
Thanks for all your help and I'll see about getting out to the fiero farm as well and maybe I can pick one up for a few bucks. If all else fails I'll havea friend at the pontiac dealership that loves the fiero and offered to mess with it at the dealer in his spare time. I'll let ya know how it goes...

Thanks,
Jason

[Slugger17]

It sounds like your idle is set real high. Look at the throttle body and on the lever that has a cable that goes to the gas pedle there should be a bolt that pushes it. If you lossen the jam nut then turn it either way to raise or lower your idle. If it does have the jam nut make sure you retighten it. That should fix your problem.

[Crashdocs]

Woohoo.... What a good Labor day weekend!!! I found the problem, MAJOR leak. My EGR tube was broken off under the upper intake manifold, couldn't see it or hear it with the roar of the engine.... Thanks for all your help. I'll post my next fix here in a few minutes


Jason

[Ragtop_Renegade]

Sweet deal. I never thought of the egr tube as a possible source of extra air in the fuel mixture, and the way they hide under the plenum makes them hard to spot. Great work!!!!! FYI on a previous post, there's no way the closed throttle adjustment screw could be set high enough to make the engine stay at 5500 RPM, it simply doesn't have that much travel.

[palaima1]

check the vacumn line at the back of the throttle body...it's about 1/2" diameter and connects to the manifold behind the base of the distributor