erratic running problem

[wargriff]

Have had a problem with my car running at low speeds, and also after having a run it just stalls or searches for revs.

Have had it looked at and seemed to behave for short period (1wk) but now back to how it was.

Had been advised that it may be a new airflow meter needed, so replaced that last week...no difference...have had all the output and volts checked on AFM and the cool temp sender ( may be wrong name) and they are all fine..

Now it is running very rich and £40 of fuel only gets me about 80 miles at present, regardless of how i drive..it also suddenly gets very non responsive every now and then, at different speeds..feels like there is some blockage, then it clears itself..

has anyone got any experiences similar and if so how the f*** did you cure it, as it is really pissing me off now..and costing me a fortune in fuel...


any help greatly appreciated..

marc

Edited by wargriff on Wednesday 1st October 15:38

[tvralfagtv6]

you do not say whether it is open or closed loop, i.e precat or not, what I will say from BMw experience, was that something as simple as the water temp sensor for the ecu not the guage!, told the ecu to run horribly rich, same with air temp sensor which is part of your AFM on a trevor, measure all of them warm.I am sure the combined minds on here will eventually get you in the right direction. I have an original sd1 manual which I can look at what the sensor values should be . is your throttle pot and all the basics set up per the rpi website. Hope this helps

[wargriff]

tvralfagtv6 said:

you do not say whether it is open or closed loop, i.e precat or not, what I will say from BMw experience, was that something as simple as the water temp sensor for the ecu not the guage!, told the ecu to run horribly rich, same with air temp sensor which is part of your AFM on a trevor, measure all of them warm.I am sure the combined minds on here will eventually get you in the right direction. I have an original sd1 manual which I can look at what the sensor values should be . is your throttle pot and all the basics set up per the rpi website. Hope this helps

Thanks for your reply, the sensors have all been checked to see if the output is ok..and im told they are all working fine..but to be honest im not at all technical and am taking the people who did it at their word..

[tvralfagtv6]

Just found this on the chim side



http://www.pistonheads.com/gassing/topic.asp?h=0&a...

[wargriff]

thanks..will get it checked tomorrow...if that fails i will fine a box of matches and some spare fuel...

[blitzracing]

If the car has catalysts the ecu should control the mixture very accurately. If it running that rich, the outputs from the lambda probes will run at .7 (or more) volts all the time and the ECU will flag up an error code if you plug a code reader into the socket on the ECU. Any half decent Range Rover dealer should have access to one, or there are individuals on this forum who will hire them out. The ECU has a good range of error codes, and should also flag up an error if one of the sensors is out of range. In my experiance rich mixtures can be caused by an AFM, a misfire, an open circuit temp sensor, or over high fuel pressure, but it gets expensive simply throwing bits at it without diagnosis. You may not get a fault code if something is just marginal however.

On the pre cat cars, the setting on the side of the AFM controls the idle mixture, and can easily be set too rich. Personnaly I dont like the RPI method of setting it to a fixed voltage output, as there are too many variables that can affect the overall mixture. Much better with a CO meter or such.

Mark