Throttle Pots.

[rtg]

A productive weekend of fault finding why the S is rough idling - to cut a long story short...

The throttle pot was replaced with new/ebay unit 2 years ago. the car has done 5k summer miles since then. Diagnosing the rough idle, I measured the ratios with a DVM - all seemed fine. I then measured the wiper voltage, ground and supply voltages with ECU on with the DVM - again all good.

However, all signals to the ECU seemed good, so out with the scope and monitored all signals to ECU. AFMs, temperature were clean, continuous and operated within spec. However, the throttle pot was showing discrete jumps in voltage when the butterflys are/near closed. Away from the closed position it was smooth and linear.

So, a high resistance, worn track confirmed when I replaced it today with a new throttle pot and the idling is super smooth.

So the question is - why are the throttle pots failing so quickly? I'm sure ford didn't replace them on sierras every 2 years, so is this a low quality version? Is there a high quality version available? i.e. a Hall effect position voltage sensor?

[MisterTee]

An interesting point about TPS replacement on Fords - but when I took my car for an MOT last week, the guy that did the MOT worked on fords years ago and mentioned that the TPS and ISCV were common weak spots on our engines. maybe they were replaced fairly regularly!?

Andy