Throttle body issue, Stuck High Idle after gas pedal pressed.

[Chrimson85]

My Truck is 1989 K2500, engine is a 5.7 350 TBI with 4spd Manual.

The problem started after the truck sat for a while. The issue is that when the gas pedal is pressed the truck's idle climbs and doesn't come back down. I have to turn the ignition off to stop it from self destructing.

I've replaced the accelerator cable and didn't fix the problem.

I can manually rev the engine at throttle arm, but need to manually push it back to lower the idle, I can feel a bit resistance which i suspect is causing my issue. I've sprayed PB blaster around the butterfly shafts where the springs are and manually worked the arm still didn't fix my problem.

I'm currently about to rebuild the throttle body and give it a good cleaning, got a new TPS and IAC coming as well. Not sure what else to do if these don't fix my problem.

Was looking for another TBI base at the junk yards but apparently they have all been scooped up, not sure why, maybe aluminum or fuel injectors.

 

[fancyTBI]

Throttle shaft is binding. A rebuild with new bushings will fix that. Are you doing the rebuild or farming it out?

 

[89RCLB]

Throttle shaft bushing kits are available here:

3/8″ Throttle Shaft Bushing Kit – Cliffs High Performance Quadrajets

 

[someotherguy]

My Truck is 1989 K2500, engine is a 5.7 350 TBI with 4spd Manual.

The problem started after the truck sat for a while. The issue is that when the gas pedal is pressed the truck's idle climbs and doesn't come back down. I have to turn the ignition off to stop it from self destructing.

I've replaced the accelerator cable and didn't fix the problem.

I can manually rev the engine at throttle arm, but need to manually push it back to lower the idle, I can feel a bit resistance which i suspect is causing my issue. I've sprayed PB blaster around the butterfly shafts where the springs are and manually worked the arm still didn't fix my problem.

I'm currently about to rebuild the throttle body and give it a good cleaning, got a new TPS and IAC coming as well. Not sure what else to do if these don't fix my problem.

Was looking for another TBI base at the junk yards but apparently they have all been scooped up, not sure why, maybe aluminum or fuel injectors.

Long shot here but if your truck is equipped with cruise, try disconnecting the cruise cable at your throttle arm. A few people have had trouble with the module going bad and "pulling" on the cable when it shouldn't. Not common.

Richard

 

[Chrimson85]

Long shot here but if your truck is equipped with cruise, try disconnecting the cruise cable at your throttle arm. A few people have had trouble with the module going bad and "pulling" on the cable when it shouldn't. Not common.

Richard

No cruise control on the truck very basic model doesn't even have AC. Thanks for the tip though in case I do aquire a model with cruise.

 

[Chrimson85]

Throttle shaft is binding. A rebuild with new bushings will fix that. Are you doing the rebuild or farming it out?

I'm doing the rebuild, seems easy enough from everything I've watched and read.

 

[Chrimson85]

Throttle shaft bushing kits are available here:

3/8″ Throttle Shaft Bushing Kit – Cliffs High Performance Quadrajets

Much appreciated for the link I'll pick up the kit, if after a good cleaning and rebuild doesn't fix my issue. Will report back on this.

 

[Chrimson85]

Took apart the TBI. Nothing really stood out other than a good cleaning. The the butterfly valve open and close with no issue. However the fuel pressure regulator has what looks like a piece of spring or part of the assembly sticking out. My question, is this normal? I've provided pictures. Also if not, anyone have a source on buying just that part for the TBI?

 

[Chrimson85]

Took apart the TBI. Nothing really stood out other than a good cleaning. The the butterfly valve open and close with no issue. However the fuel pressure regulator has what looks like a piece of spring or part of the assembly sticking out. My question, is this normal? I've provided pictures. Also if not, anyone have a source on buying just that part for the TBI?

So apparently this little metal piece sticking out of the fuel regulator was just some welding wire. Apparently the regulator is welded to keep the fuel pressure from being adjusted. so just ripped it off. Continue to rebuild the TBI and replace the IAC and the TPS. Put everything back together after a good cleaning and new gaskets. No more rocket idle or sticking throttle.