M42club.com - Home of the BMW E30/E36 318i/iS

DISCUSSION => Engine management => Topic started by: MrAlan on December 10, 2010, 05:18:17 PM

Title: Erratic idle on my M42
Post by: MrAlan on December 10, 2010, 05:18:17 PM

My idle is hunting up and down from 1000rpm down to nearly 0 then back up again, occasionaly it goes so low it cuts out.
Ive replaced the Idle control valve and it didnt change, ive checked the boot rubbers and the airflow meter, Im just at a complete loss to whats causing it :( Please can anyone help?

Title: Erratic idle on my M42
Post by: superpotter80 on December 10, 2010, 05:27:59 PM

mine was hunting up to 1500rpm then down to 500rpm turned out to be the lamda sensor

Title: Erratic idle on my M42
Post by: MrAlan on December 10, 2010, 05:52:33 PM

interesting, i hadnt thought of that, ill check it and see, thanks

Title: Erratic idle on my M42
Post by: Warsteiner on December 11, 2010, 10:06:24 AM

I also have a dithering idle and had my buddy put it on his GT1 BMW diagnostic computer and found the issue to be with the O2 sensor.

Cheers,
~Ralph

Title: Erratic idle on my M42
Post by: MrAlan on December 14, 2010, 02:42:04 PM

Quote from: Warsteiner;99518

I also have a dithering idle and had my buddy put it on his GT1 BMW diagnostic computer and found the issue to be with the O2 sensor.

Cheers,
~Ralph

thats something im looking into, i think despite already looking that the airflow meter could be my problem.. i started the car without it connected and it ran better! soon as i re connected it started surging again. Im going to replace AFM then if that doesnt work the lambda sensor. Its also possibly the Throttle position sensor which turns out to have similar symptoms.
Ill get there and post when ive solved it.
Thanks for help, Alan

Title: Erratic idle on my M42
Post by: MrAlan on December 18, 2010, 05:01:50 AM

You guys were right its my Lambda sensor, i changed it last night with a cheap £30 universal one and its purrfect! :) thanks for help!