If engine idle rolls up and down, and diagnosis rules out Idle Air Control (IAC) valve issues and vacuum leaks, the Programmable Speedometer/Odometer Module (PSOM) can be at fault electronically. The instrument cluster will need to be replaced, the PSOM is inside the cluster.
Average mileage: 126,702 (120,000–140,108)
Engines affected: 4.6L V8, 5.8L V8
7 people reported this problem
Viewing 1 - 3 of 3 comments
revs /high idle (very) in park. disconnected the ICV for a time and it ran fine without it except backing up (not enough idle speed then). bought new on be, cleaned throttle body and found leak in hose_all fixed. found new issue but impossible to find part...
idle surges at stop and in park. tired of throwing new parts, no vacuum leaks
The engine would randomly 'race' without warning. I would have to keep foot on brake at stoplights etc. to keep it from 'jumping out' into traffic. We tried vacuum hoses, egr valve. Doing it again.