Hunting on idle & High Emissions on Idle !!Help Needed Please
 

Hi,

Got a 1998 UK Impreza, Been in for M.O.T and failed on High Emissons. It is also suffering Eratic Idling.

Had a garage rin a Diagnostics test on it and there was no fault codes and they couldn't see alot wrong on the computer either.

Has nay one gor any idea's before i start replacing things.

Check for split hoses, check the MAF sensor and check that the exhaust manifold isn't blowing anywhere. Also clean the idle control valve. Clean up the engine earth and check the plugs and leads.

Sounds like it could be the lambda ?

Dave

I unpluged the Lambda sensor and nothing changed with the engine at all, Does that mean anything.

a knackered dump valve also causes it to hunt ! or aftermarket crappy ones !

Did you put a different exhaust on to get it through the MOT?

If so this happened to me too, I fitted the standard exhaust as I had a decat. Could just be the ECU learning to deal with the new exhaust. If this is the case try resteting the ECU.

It has had the same exhaust from new on it, How can i test the Lamda sensor, but as i say, it past emmisions on fast idle!!