E30 Zone

First drive since september new mot sunny day every thing sweet except idle speed , idle speed sits at 550rpm when fully warmed up after a couple of hours driving .Revs dip slightly[500] when pulling up to junction etc then rise to 550rpm and stay constant .Car drives fine in all respects but just little concerned as it idled at700 ish before I took it of the road last year . Idle control valve seems fine & no leaks anywhere .Any ideas welcome many thanks

Have you tried disconnecting the battery or ECU and making it relearn the base idle settings by letting it idle for at least 10 mins, switching off, then going for a drive?

Speedtouch, im abit confused by your post please exscuse me, when you say diconnect the battery or ecu are you saying do this when the car is running, I,m just wondering how would the engine run with the ecu diconnected, obviously the engine would run without the battery connected sorry to be a halfwit
Also cozmic you could have a look at the throttle cable adjustment to see if it requires a small tweek to speed up the idle.

hey problem solved after pulling all induction elbow & associated stuff off to check throttle etc ,&couldn't see anything wrong ,disconnected battery so ecu went to default still the same ,went for drive with the missus sat parked up [engine idling ] commenting on how it still sounded sweet &even , missus noticed dusty instrument facia , as I wiped it clean Revs rose to 700ish [sticky rev needle ] . I may be 6ft 6 but at the moment I feel about 3inches especially after throwing the toys out the pram when the wife said :are you sure its low it sounds fine to me : just goes to show it ain't always doom & gloom & occasionally my wife does have something to say worth listening to thanks to all who tried to help . happy day after all

TRANSPORTER wrote: Also cozmic you could have a look at the throttle cable adjustment to see if it requires a small tweek to speed up the idle.

What has the throttle cable got to do with idle speed?

Was thinking that maybe over time the cable may of got un-lubricated or out of adjustment on the linkage on top of the throttle body, only saying as the last owner of my Touring had done all sorts of nasty things under my bonnet some of which I,m still rectifying, but one of them was the throttle cable was set too loose and had to be put right for correct idle speed and lubrication of cable.

A throttle cable that is too tight can obviously pull the throttle disc off its stop, and hence pull the engine revs above idle, but a throttle cable can be so slack as to be removed from the car, and won't affect idle speed in the slightest.
Idle speed is set by the ECU software, and can't be manually adjusted.

Forgive me if I'm being a bit dim but isn't there a screw on the throttle linkage that can adjust idle speed to a small degree? Obviously this is NOT the solution to idling problems but can be used to make small adjustments.

spp320i wrote:Forgive me if I'm being a bit dim but isn't there a screw on the throttle linkage that can adjust idle speed to a small degree? Obviously this is NOT the solution to idling problems but can be used to make small adjustments.

Unfortunately not, at least not on 325 Motronic as I have. I'm sure Brian's right in that the ECU sets the idle speed.
Talking of which, I have the same problem. Car idling at 550/600 instead of (what I think should be right) about 750/800? Someone told me all BMs idle at 900. What does anyone think?

Most standard 325i's idle at 700rpm, but chipped ones often idle a little higher, eg 900rpm.

M20s idle at 760 RPM +/- 40 RPM, M40s idle at 800 RPM +/- 40 RPM and are not adjustable (except for a slight increase using the aircon feeds top the ECU)
If your car idles outside of these limits, then either the tacho is giving an inaccurate reading, or there is a fault. If there is a fault, then find and cure it, not introduce another fault to mask the first fault.
The screw on the throttle body will increase the idle speed if screwed inwards, in the same way that an over tight throttle cable will, by forcing the engine off idle. DON'T TOUCH THE SCREW!

Cheers Brian, helpful as ever

I'm driving a 323 and the idling sits at 550/600. It used to be around 700+-, but after reading another thread, i adjusted the screw to lower the rpm. Lately, the fuel consumption is getting relatively bad compared to before. Could this be the problem?

When i adjust the screw so that the rpm stay at 760+-, the engine seems to be over working. Pls advice

Your engine is non-Motronic I think so you can adjust the screw. Motronics are controlled by the ECU.

I've tried removing the oil filler cap when the engine is running and the engine became slow and almost stall, does it mean that my vacumm hoses are still ok?

I've disconnected the battery and tape the vacumm hose which is crack and loosen the screw on the TB. Thereafter, connect the battery and the engine idles at 750+-. Took the car out for a spin and revving. The rpm went slightly higher to about 850-900 and stays the same and this time no matter how much i loosen the screw, it doesn't seem to affect the idling. The idling is high. What could be wrong?
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stormhunt3r wrote:...tape the vacumm hose...

That's what's wrong. Replace it with a new item, it's £20 or thereabouts. Check your other vacuum hoses too.

Stewart

Speedtouch wrote:Have you tried disconnecting the battery or ECU and making it relearn the base idle settings by letting it idle for at least 10 mins, switching off, then going for a drive?

Sorry for the thread hi-jack, but i took my battery out yesterday to charge it, and found that my idle was about 500 today aswell.

I've driven it and it doesn't seem quite right, should i leave it idling(sp) or should driving it sort it out?

Battery was out for about 3-4hours, possible slightly longer.

stranter wrote:

stormhunt3r wrote:...tape the vacumm hose...

That's what's wrong. Replace it with a new item, it's £20 or thereabouts. Check your other vacuum hoses too.

Stewart

i was about to get a new set of hoses. Will try it later with the new hose to see if the idling would be normal.