Intermittent increase in engine revs

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lauriepo

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I have a 2002 DHSE 2.5l Range Rover.
The car starts fine and drives well but after 30-40 miles things go wrong. I can be driving at 40mph~2000rpm and the revs will jump 500rpm. If I have to start it's reluctant to change gear, then after a few minutes it goes back to normal. It will even do it when the car is stationary and in park, revs increase 400ish rpm. Its almost is if someone is flicking a switch off and on. It started six months ago and is getting progressively worst.
I have changed the oil and fuel filter. Changed the Gearbox oil and filter and it changes between all gears smoothly.
Replaced all the vacuum pipes, the MAP sensor, ERG valve, crank position sensor and the throttle position sensor. I borrowed a moded ECU but it gave the same results.

Whats next?
 
Don't know the vehicle but does it have a TPS (throttle position sensor)?
If so, could it be faulty and "asking" for more "go"?
 
DanClarke said:
Don't know the vehicle but does it have a TPS (throttle position sensor)?
If so, could it be faulty and "asking" for more "go"?
Click to expand...
I have fitted a different TSP from the scrap yard and got the same result. If something is asking for more fuel woulnt the car accelerate, cos it dont..lp
 
It really needs diagnostics, but check if there is a hot start mod fitted, if there is it might be failing. The engine ECU temperature sensor failing can also cause the revs to rise if the ECU suddenly thinks the engine is cold.
 
The revs will change a bit as the aircon kicks in and out but only by a few hundred rpm. If it only does it while hot I wonder if a sensor is failing and it is using default values? As Datatek says there's the temperature sensor but there's also #4 injector. I cannot recall if it can run using the #4 injector values if the crank position sensor fails but it would say in RAVE.
 
lauriepo said:
I have a 2002 DHSE 2.5l Range Rover.
The car starts fine and drives well but after 30-40 miles things go wrong. I can be driving at 40mph~2000rpm and the revs will jump 500rpm. If I have to start it's reluctant to change gear, then after a few minutes it goes back to normal. It will even do it when the car is stationary and in park, revs increase 400ish rpm. Its almost is if someone is flicking a switch off and on. It started six months ago and is getting progressively worst.
I have changed the oil and fuel filter. Changed the Gearbox oil and filter and it changes between all gears smoothly.
Replaced all the vacuum pipes, the MAP sensor, ERG valve, crank position sensor and the throttle position sensor. I borrowed a moded ECU but it gave the same results.

Whats next?
Click to expand...
Check your engine relays mate I've had symptoms like that before or your bcm plugs might be a bit wet
 
The sensors under the inlet manifold are front is diesel temp middle one is ecu temperature and the back one is water temperature sensor mate
 
Just try unplugging MAF sensor, the one next to air filter box, have had similar with one failing. Will run without MAF plugged in as uses default settings
 
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