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.
Engine Idle Rolls Up and Down on Ford E-150
Average mileage: 120,000 (120,000–120,000)
Engines affected: 4.6L V8, 5.8L V8
4 people reported this problem
1 person shared problem details
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.
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