Engine Idle Rolls Up and Down on Ford E-150

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.

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Average mileage: 126,702 (120,000–140,108)
Engines affected: 4.6L V8, 5.8L V8
3 model years affected: 1992, 1993, 1995
6 people reported this problem
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problem details
1995 Ford E-150 - 5.8L V8 140,108 mi,
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...
1995 Ford E-150 - 5.8L V8 120,000 mi,
idle surges at stop and in park. tired of throwing new parts, no vacuum leaks
1992 Ford E-150 - 4.6L V8 120,000 mi,
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.