pullinhd

My wife has an 02 Jeep Grand Cherokee with the 4.0. Its seems to have a mind of its on when you start it even in warm weather it will rev up really high and stay there for quit a while. It also just revs up on iits own in short little burst when your running down the highway. Does anybody have any Idea what this could be.

Hymie

Some thoughts on your reving problem….

I have a 2000 Grand Cherokee 4.7L, which I suspect of misbehaving, but not quite so badly as you report.

Jeep should really be interested in understanding what is clearly a potential major safety issue on their vehicles.

I would not recommend you take the vehicle to a garage to investigate an intermittent fault such as this – they will invariably charge you mega-bucks for no fix.

I take it that when this happens, your engine warning light does not illuminate, indicating a fault?

I am suspicious that the fault lies in the Throttle Position Sensor (TPS), which feeds a voltage to the Electronic Control Unit (ECU), telling the on-board computer how far you have depressed the accelerator.
The TPS is a sealed unit, a bit like a volume control on an amplifier.

To test my theory that it is a faulty TPS, when you next experience the fault, adjust the accelerator position (either up or down), which will change the output voltage from the TPS. If this results in the vehicle ‘waking up’ and setting the engine speed in accordance with the accelerator position – it may very well be due to a faulty TPS.

You could then take a chance on having the TPS changed, at around $30 + labour.