L-Series idling too fast at times

A friend has a 1998 L-Series. On occasion it will idle at 2000 rpm and then return to normal. When changing gear the revs drop to 2000 rpm and no lower. This problem is intermittent. May be ok for a day or two, then it starts again. Any pointers as to what may be the culprit? Could it be MAF sensor, or maybe MAP sensor? Or CPS? Anyone had these symptoms before? Any advice will be appreciated - before he torches it... and gets a Disco...!!!:doh:

Well, it isn't the MAF sensor as it doesn't have one. Most likely possibility is the throttle position sensor, which is known to go AWOL at times. Does he have the air con on at the time? If I'm parked with my air con on and I just give enough throttle to bring the engine off idle then as the air con cycles in and out I get exactly what you describe.

Thanks Darmain. I was inclined to think maybe the CPS. Rave talk about if this sensor is faulty the ECM uses the signals from the needle lift sensor. This results in loss of performance and increased iddling speed according to Rave (page 313). His performance is not as good as my L-series by quite a margin. I have told him to check the throttle position sensor as well. Not sure if he had the aircon on...I assumed not. A Landrover mechanic worked on it last night at his home and messed with the injector pump and timing and now it won't start at all (he did get it going with a cloud of white smoke, but in the morning it would not start at all). He (L/rover mechanic) will continue to work on it tomorrow as it is still at his house. He changed injector pumps (for a reconditioned pump)and it made no difference either.

Crickey, he's a brame man. The pump is a pain to get set up straight, and if there are other problems with the engine as well then I'm surprised it runs at all. I would recommend that the CPS is replaced just to rule it out. Its a lot easier to replace than the fuel pump.

Other sensors to watch out for are :

Coolant temperature sensor;
Air intake temperature sensor;
Needle lift sensor;
Mass air flow sensor.

I appear to be slightly mistaken, there is a MAP on this engine and its mounted on the bulk head, with a pipe connected to the turbo discharge port. I doubt this affects idle but put it down the list of possibles.

I'd check out all of these before touvhing the pump. Too late it seems....

Keep us posted on what you find.

I agree with you....pump is last thing I would have touched. I will hear on Monday what the outcome was. I drove past the mechanic's house this afternoon and see the Landy was parked in the street... so it must be running again. Later it was gone, so he must have delivered it to my foriend who lives in another town about 30 km away. If it is still acting up we can work through the sensors one by one.

Freelander is back on the road again, but still has the problem iddling intermittently. When the problem occurs a fault light on the dash lights up, and goes off again. Today it is running fine. Tomorrow he is going to check the sensors (CPS, MAF, TPS and MAP).

He ended up cleaning all connectors etc. and it is still running fine after a few days. Could not pinpoint the problem to anything specific.

I'd be reaconing you might have a wire loom issue there. Been know to happen.

I found this helpful...
L-series diesel self revving

Cheers

Blippie