Mechanics

RANGE HIGH IDLE

1999 Rover Range Rover

Electrical problem
1999 Range Rover V8 Four Wheel Drive Automatic 115000 miles

Sir
I have a Land Rover Range Rover 4.0 year 1999.
It has a high idle of 1200. The smog people told me it should be 800.
I have two similar cars so I can swop parts to see if what I think is faulty is true.
I have changed the idle throttle position sensor, and the mass air flow sensor.I removed from the good car one by one and fitted on the faulty car but I got no change.I left the faulty parts in the good car and they are working fine.
I hate to take it to the dealer as they will skin me.
Please help what I can try again
Avatar
Sembhi
June 2, 2009.




Is there a check engine light on? That's where we need to start. Perhaps it will tell you if the system it LEAN, indicating a vacuum leak. It may not be that simple, though so lets start by checking for diagnostic trouble codes.

Tiny
Jasonray
Jun 2, 2009.
There was no check engine light. But I just checked the codes anyway and there were no codes.
Yesterday I removed all connections and removed the throttle position sensor and the mass inflow sensor and put it back for the third time. On starting it the idle corrected it self to 800. However when I went to smog and the car was warm the high idle came back.

Tiny
Sembhi
Jun 2, 2009.
Do you have a scan tool or just a code reader? If you have a scan tool, look at the IAC pid. It should read 20-25 steps and the MAF sensor should read approximately 1.4 volts at idle. When the engine temp is cool, it will be in 'open loop' and when it warms up, it will go into 'closed loop' and will start adjusting various things based on sensor inputs. When in open loop, it's running on preset values within the PCM/ECM. This could explain why it idles correctly when cold but the idle raises when it warms up. Something is telling it to idle up. You'll need a scan tool to determine what, though. Start by watching the IAC steps and the MAF voltage. Let me know what those values are and we'll go from there.
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Tiny
Jasonray
Jun 2, 2009.
Sir
i dont have a scan tool I only have a code reader. Where do I get a scan tool and how costly is it
regards

Tiny
Sembhi
Jun 2, 2009.
You can buy one at 'Oreilly's' or online. They're pretty pricey tho. You will a lot better off to take it to a shop and let them do it. They'll be able to monitor all the inputs from the sensors and determine why the idle goes up when it goes to closed loop. That stuff can get pretty technical. Just check all the basics first. Make sure there are NO vacuum leaks. Do you hear any 'hissing' noises while it's running? I sometimes spray some carb cleaner around and see if the rpm's fluctuate any. If no vacuum leaks are found, take it to a shop and let them take it from there. I'm sorry but that's pretty technical stuff and hard to deal with without the proper tools.

Tiny
Jasonray
Jun 2, 2009.
I did try it with the carb cleaner and there are no leaks. Thank you for your advice. If io take it for a diagnose can they really pinpoint the problem to the excat cause or will they also try this or that
regards

Tiny
Sembhi
Jun 2, 2009.
Well, it's hard to say. If you brought it to MY shop, I would ask you a lot of questions about what all you've done and haven't done. So offer that info to whoever you take it to. That may save them some time and you some diagnostics costs. But, even knowing what you've already tried, I would still probably somewhat start from scratch just because I've been doing this for 20 years and I kind of have a routine for diagnosing problems. It would not be because I'm ignoring you, but just to satisfy myself. Good luck and let me know if I can help you in any way.

Tiny
Jasonray
Jun 2, 2009.
Thank you very much

Tiny
Sembhi
Jun 2, 2009.

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