erratic idling

[magnus]

HELP--I have had this fault for yonks on my 5L chim. Starts off fine--steady 1000 rpm--first thrash when engine warm and it all goes haywire--idle drops to cutout point (AND cuts out sometimes) then leaps to about 3000 driving becomes lumpy etc. I have Steve's bible which is not too clear on how to proceed on a step-by-step basis. I have cleaned and checked stepper motor and I have cleaned throttle housing and, checked for air leaks. Can any of you knowledgable guys out there tell me the next step in systematically tracing this fault.

[G-Man]

Having the same problem with my Wedge at the moment. not sure if its fuel or electrically related.

[jigs]

I would suspect the speed sensor as it's after a thrash that it misbehaves. Don't know if they can be reconditioned or if it has to be replaced.

[shpub]

jigs said: I would suspect the speed sensor as it's after a thrash that it misbehaves. Don't know if they can be reconditioned or if it has to be replaced.

Or the lambda sensor or the temp sensor or the throttle pot or.....

Time to get a professional to plug in thousands of pounds worth of diagnostic kit and see what is going on.

[martyn lane]

I have the same problem with my 4l chim. So bad that it offen cuts out and wont start again. I found that if i remove the electric plug from the air flow sensor it starts up, then replace the plug and away you go again until the next time. Does this help anyone to pin point the problem?

[magnus]

martyn lane said:

I have the same problem with my 4l chim. So bad that it offen cuts out and wont start again. I found that if i remove the electric plug from the air flow sensor it starts up, then replace the plug and away you go again until the next time. Does this help anyone to pin point the problem?

Martyn--thanks for email--YES, wonder of wonders, it WORKS!! Now what the hell do I deduce from this?? Any ideas Steve?
Magnus

[shpub]

All that this does is force the ECU into a limp home mode where it uses a default mapping or there is a bad connection on the air flow connector or a dead air flow meter (costs around £300 BTW so you need to make sure it is the culprit before spending any money).

You can disconnect many of the sensors and the ECU will get the engine started but it ain't running right. See limp home section in the bible.

The problem is that unless things are obvious like a bad connection, almost anything connected with the system could be responsible. Replacing them on the basis of it cured my car will run up bills of many many hunbdreds of pounds with no guarentee of success. As I said, time to say - HELP!

>> Edited by shpub on Wednesday 18th June 07:20