Crap idle M42

[Robinson]

I gather this is a common problem, and the air mass sensor is the cause?

Idle is rough pretty much permanently. It might be normal though.
Mods:

Chipped uk off shelf chip
Cam timing adjusted(supposedly, can definitely cause this)
Heater plate removed

I am thinking that perhaps returning it to standard spec would improve it greatly? Or should i just buy a new air flow sensor or whatever they call it on these cars? Would cleaning the sensor flap hinges etc up with carb spray work?

Idle control valve need cleaning?

Any ideas welcome, i would rather find the cause by testing/fiddling than just throwing cash at it.

[jmc330i]

Check for any air leaks in the rubber hoses/pipes. If its drawing in any unmetered air it will idle badly.

[Robinson]

surely it would idle higher though? it idles pretty low at the moment. there are various hoses jutted about that look like they should be connected somewhere, i will have to take some pics.

Will give it a thorough check over on sunday ta

Any other ideas?

[Pal318is]

Check your leads...

Pal

[Robinson]

I need to replace the leads really, and clean the air flow meter, throttle body and idle motor stuff really. then check for inlet leaks etc, and see what it does. i'm thinking the heater plate really needs to be there for it to run correctly for how it is mapped? And the superchip and cam timing won't help. A bmw engine should purr nicely i am sure, not a chugging at idle.

[Gwynleym10]

I'd check the cheap things first, vacuum leeks clean the parts with carb cleaner.

Did it ever idle ok with the chip? Does it idle OK with a standard chip?

Crap timing will make it idle badly

[Robinson]

I bought the car as it is a few weeks back. It did idle ok breifly for a while, sometimes it's alright and other times it's not. Never run spot on though since i got it. But then it just needs some TLC i'm sure.

[kevin316i]

Give the car a good service first including plugs and filters, then check for vacuum leaks.

[Robinson]

Did the plugs last weekend, and checked air filter which was still clean, oil has been changed recently. Need to change fuel filter i think, don't even know where it is, haynes manual to the rescue lol

[abelai]

My friends 318is was idling like a dog and when we changed the cam chain noticed that the sprockets on the cams had twisted round as they have a small amount of adjustment in them not sure why but we realigned them to their standard setting and the idle was perfect. Not saying this is your problem just that its something to check.

[Jamese30]

I posted about rough idle on my m42 a week or so ago aswell Robinson.

After close inspection I had som cracks in the vacuum pipes under the inlet manifold and some of the pipes were very loose on the joints. All fixed now and the car idles better, so give these a good going over!

One pipe especially is where the vacuum pipe goes into the idle control valve (between the cylinder head and bulkhead) - on mine this was very loose.

Good luck,