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Matt, Mechanical Engineer
Category: Car
Satisfied Customers: 22762
Experience:  BEng hons Mech engineering, in auto industry 22 years
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P38 2.5 dse 1997 Rangerover idle is at 2100rpm with fault

Customer Question

P38 2.5 dse 1997 Rangerover idle is at 2100rpm with fault via Hawkeye - engine speed sensor, replaced both engine temp sensors and the crankshaft sensor - unable to get idle down to normal 820+-rpm any idea where to look next
Submitted: 3 years ago.
Category: Car
Expert:  Shantal-Mod replied 3 years ago.
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Customer: replied 3 years ago.

Had no answer to my question - still trying to solve the problem

Expert:  Matt replied 3 years ago.

when you have a high idle speed on this engine its well worth checking to see if its running off its own engine oil

so 1st check the crankcase pressure relief valve (PCV) these are sprung loaded and are only meant to 'burp' excess pressure every now and then. The exiting gas is piped back to the inlet , however should the valve stick open then the engine tends to suck the air out of the crankcase all the time and this carrys oil over with it.

If you remove the air intake pipe and look inside where the crankcase breather is plumbed in you may find evidence of oil.

If you do find oil replace the valve. If this is all OK then its possible that the valve stem seals are past their best and are drip-feeding oil into the intake. These can be replaced without removing the head by a competent garage in half a day or so

Also check inside the intake just after the turbo for any signs of oil as this would be an indication that the turbo oil seal is starting to fail and a replacement / rebuilt turbo may well be required. Have a feel of the turbine wheel - there should be no play radially at all - but a little bit of axial / end to end float is normal
Customer: replied 3 years ago.

thanks for the suggestion there is no oil drawn in throught the intake, the valve stems were renewed - this high idle is occuring even on a cold engine


Expert:  Matt replied 3 years ago.

to adjust the idle there are 2 points

The throttle cable will end at an arm on the injector pump. This will rest against a threaded bolt when at idle- just wind the bolt out to lower the idle speed as low as it will go 1st

then there's also another bolt adjuster screw on the little arm at the front off side of the pump this is the governor setting and you adjust the speed with this

for this to work properly the throttle arm must be in its correct position at the bottom of its travel
Customer: replied 3 years ago.

The p38 is fly by wire no throttle cable

Expert:  Matt replied 3 years ago.
Hello OK

sorry about that

the only idle speed adjustment with the fly by wire system is done using the BMW diagnostic tool

however from your description its too high for a simple software tweak and I'd say the fault lies with the throttle pedal sensor