s50 idle rough

[moggie]

hi all,i will try and describe this as best i can,
ive just completed my s50b32 e30 and it ran perfect until i took it for first long drive,it runs fine when driving it,pulls strong and doesn't miss but when its at idle its got a bit of a miss/surge which makes the car rock a little,the rev needle sits in the right place and doesn't seem to surge with it.
its had a new fuel filter,
ive checked all vacuum pipes and renewed any cracked ones including the little tee piece cap,
ive run some injector cleaner through it,
plugs all look fine but ive ordered new anyway,
ive cleaned the maf,
ive unplugged the throttle position sensor when running and it doesn't alter the sound,
ive also cleand the idle control valve,
would plugging it in show any faults ?
any help please!!

[moggie]

changed all plugs and still no luck,has anyone had any problems like this,could it be an injector?

[moggie]

had it plugged in today and its not showing any fault codes on ecu,anyone no any bmw specialists in west yorkshire area?

[moggie]

No one?

[DanThe]

Have you checked all elec plug connections? Its not unknown for them to be loose, especially where they clip through a bracket

[moggie]

yes dan,ive checked all i could find and they all seem ok but i will have another go at them,really annoying as it runs perfect when driving it and just idles rough,i thought it might have been oil on the air flow meter from the k&n filter because it only started doing it after its first long drive but ive had that out and cleaned it with carb cleaner and its no different

[moggie]

you're ews delete worked perfecly by the way,ive got it booked in on Wednesday with a guy who looks after my brothers cosworth who is good at fault finding so lets hope he can tell me what it is causing the rough idle

[moggie]

diagnosed as air mass meter so ordering a new Bosch one and see if that cures it,fingers crossed.

[moggie]

put on a brand new bosch air mass meter and still not cured it any help as im pulling my hair air out here

[sweep]

Is there a air leak?

[moggie]

ive checked every vacuum pipe,sprayed around everywhere with brake cleaner and lpg and cant find any air leaks,im going to re check everything at weekend but im pretty sure theres no air leaks

[DanThe]

Have you taken the plenum off to get at every joint?

[moggie]

twice dan,but im going to take it off again just to make sure because is does seem like a slight vacuum leak and now the maf is eleminated i cant see what else it can be

[moggie]

has anybody got edd china"s number

[e30rapidic]

O2 sensor?

[moggie]

definitely no air leaks

[HenryM3]

Try 02 sensor, I had what was termed as a lazy 02 sensor, didn't show up on diagnostic but it cured similar fault.

[moggie]

cheers henry il give it a try

[moggie]

runs same with no 02 sensors not plugged in,
ive got the e36 m3 evo pump in e30 hanger ,is there any way in which it could be a fuel pump faulty ,[bought second hand],it also seems to have slight hesitation from idle to 2000rpm

[Mikey_Boy]

Just a thought - if it runs the same without the O2 sensor connected, I would suggest that might be your fault right there. The O2 sensor 'trims' the air fuel mix from the map to get the lambda reading spot on - if that isn't working it will idle rough and run ok through the rest of the RPM range (at part load it trims until fuel is needed for cooling but you either won't notice its effect or it might feel like a hesitation) and at full load the O2 sensor usually does very little.

Hope that helps...!

[Mikey_Boy]

And just for reference fuel is needed for cooling above 3000rpm normally, so from what you describe, I would try O2 sensor next... It's effect is most pronounced at idle condition.

[jmc330i]

Would having the O2 sensors in the wrong downpipes cause this? (I mean the sensor for cyls 1-3 in the downpipe for 4-6 and vice versa)

[moggie]

would it not throw a code if it was the 02 sensor/lamba sensor?

[HenryM3]

Didn't on mine, don't know if that was down to the fact that it was working but just not properly.

[moggie]

exhaust sensors ordered ,keeping fingers crossed

[moggie]

exhaust sensors not cured it ,really annoying!

[Osamam3]

Here is a detailed post on your problem

http://www.pistonheads.com/gassing/topic.asp?t=610143

[Osamam3]

http://www.pistonheads.com/gassing/topic.asp?t=610143

[Demlotcrew]

Have you had a vanos test carried out?

[Osamam3]

My car is doing the same and I believe it to be the vanos seals. I am ordering after new year and will have a go at it.
Was this ever fixed ?