BMW M42 318is Starting fault - fluctuating revs

John Avis by | July 3, 2010 | My 1994 318is

When I start my M42 powered 1994 E36 318is the revs jump up to about 1500 then drop down to almost stalling speeds, then go up and down a few more times, then stabilise at normal idle speed, about 800rpm.
When I start my M42 powered 1994 E36 318is the revs jump up to about 1500 then drop down to almost stalling speeds, then go up and down a few more times, then stabilise at normal idle speed, about 800rpm.

I have recorded a video (no audio) of a typical start.



This happens whether the engine is cold or hot and once running there are no idle or running problems whatsoever.

The problem is somewhat intermittent. It happens most of the time but not always.

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Comments

Rein

by Rein | May 24, 2019

Bit of a late comment, but my M42 does this aswell. And sometimes it shuts down on idle when warm. I had the Lambda sensor (which was replaced some 60k km ago) checked as well as full check of all the other sensors. Nothing showed up, all seemed normal. Did you ever find the source of this problem?

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John Avis

by John Avis | May 24, 2019

No, I don't remember ever solving that problem and sold that car a long time ago. I have another 318is now (M44) which doesn't have the exact same problem but revs fluctuate when idling only when cold.

I don't think the O2 sensor is used when the car is cold, so shouldn't be the cause of this problem (unless it only happens on hot starts).

Could it be a vacuum leak? I've been thinking of trying one of those DIY smoke testers I've seen on Youtube myself. Might be worth a go?

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About me

I am a bit of a 3 series fanatic, having owned a couple of E30s and a few E36s, plus a few parts cars. I like the combination of the compact size, good performance and handling, and that they are more sports sedan than an impractical and extrovert sports car. This blog is a place to share my experience and knowledge.

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