PlatonicSolid
OBS Enthusiast
Hi All - New here - first real post.
The patient: 89 GMC C3500XC 7.4L RWD AT Stock - Jasper engine installed 2007 - Truck purchased new by my parents
It has many issues that I can live with since it's just a utility vehicle for me (radio and clock no longer function, intermittent wiper control only works sometimes, brake warning light is usually ON - had 2 different mechanics try to fix this and both failed, but brakes work fine)
Symptom: Throttle sticks high. I'm going 40 MPH on flat road without stepping on gas. Have to put in neutral while driving and kick it to return to normal idle. If I only tap the gas it will stick at even higher idle. After initial warm up in the driveway, everything is fine = settles to normal low idle. Once I start driving it settles at higher idle until I kick it down (stop sign approaching - put in neutral - kick it down - stop at sign. Repeat constantly during journey = it's basically undriveable)
I can reproduce this at the throttle body. Makes me want to put a spring on the throttle to pull it back. Throttle moves smoothly with engine off, thus i believe throttle cable is fine.
Possibly related:
O2 sensor code 44 (using flashy light method) - Don't have a code reader, but would like to get one (guidance on what to get appreciated)
Exhaust leak at flange after O2 sensor - Just noticed that yesterday
Attempts to fix throttle issue:
Replace TPS and set to 0.61V per included instructions - made no difference
Disconnect Cruise Control at TB - I never use it and don't trust the wring in the steering column as it's part of the same stick as the erratic wiper control - made no difference
Best Guess at next step:
Figure out how to fix the exhaust flange leak in hopes that maybe O2 sensor is causing throttle issue.
If that doesn't work - replace IAC
Insight appreciated
The patient: 89 GMC C3500XC 7.4L RWD AT Stock - Jasper engine installed 2007 - Truck purchased new by my parents
It has many issues that I can live with since it's just a utility vehicle for me (radio and clock no longer function, intermittent wiper control only works sometimes, brake warning light is usually ON - had 2 different mechanics try to fix this and both failed, but brakes work fine)
Symptom: Throttle sticks high. I'm going 40 MPH on flat road without stepping on gas. Have to put in neutral while driving and kick it to return to normal idle. If I only tap the gas it will stick at even higher idle. After initial warm up in the driveway, everything is fine = settles to normal low idle. Once I start driving it settles at higher idle until I kick it down (stop sign approaching - put in neutral - kick it down - stop at sign. Repeat constantly during journey = it's basically undriveable)
I can reproduce this at the throttle body. Makes me want to put a spring on the throttle to pull it back. Throttle moves smoothly with engine off, thus i believe throttle cable is fine.
Possibly related:
O2 sensor code 44 (using flashy light method) - Don't have a code reader, but would like to get one (guidance on what to get appreciated)
Exhaust leak at flange after O2 sensor - Just noticed that yesterday
Attempts to fix throttle issue:
Replace TPS and set to 0.61V per included instructions - made no difference
Disconnect Cruise Control at TB - I never use it and don't trust the wring in the steering column as it's part of the same stick as the erratic wiper control - made no difference
Best Guess at next step:
Figure out how to fix the exhaust flange leak in hopes that maybe O2 sensor is causing throttle issue.
If that doesn't work - replace IAC
Insight appreciated
Last edited: