Idle adjustment

[blue350i]

Hi,

Can any body shed some light on how to adjust the idle speed on a 350i. Mine idles at 1000 revs when warm, and should have thought 750 would be more near the mark. there is no noticeable adjustment screw and i have tried altering the throttle linkages, and even disconecting them and it still idles at 1000.

Any body else experienced this that could help

Cheers

Steve

[2 sheds]

There should be an idle adjustment screw facing down on top of and to one side of the throttle body, clockwise to decrease, if you tamper with the throttle lever you will need to reset the position sensor (potentiometer) this would be worth checking first anyway. 850 rpm is OK
Tim

[dickymint]

2 sheds said:

There should be an idle adjustment screw facing down on top of and to one side of the throttle body, clockwise to decrease, if you tamper with the throttle lever you will need to reset the position sensor (potentiometer) this would be worth checking first anyway. 850 rpm is OK Tim

All true but first check the butterfly gap is 0.002" when closed? correct me if im wrong please Tim.

[plewis66]

The idle adjustment is a hex grub screw (so an alan key is required). If you stand at the left wing and look into the engine bay, it is on the top of the plenum, just to the right of where the air hose connects.

The factory setting is two and a half turns up from bottom, and this gives me an idle of about 850. Much lower, and I get some hunting.

[2 sheds]

dickymint said:

2 sheds said: There should be an idle adjustment screw facing down on top of and to one side of the throttle body, clockwise to decrease, if you tamper with the throttle lever you will need to reset the position sensor (potentiometer) this would be worth checking first anyway. 850 rpm is OK Tim All true but first check the butterfly gap is 0.002" when closed? correct me if im wrong please Tim.

You are totally correct, but if the throttle stop hasn't been touched ?, just turning the by-pass screw alone might do it, then if it runs ok i would leave it at that, if setting up from scratch just ask and i'll post or email the full procedure.
The 2 1/2 turn theory only works if the throttle butterfly is in the correct position,
Tim

[gerry attrick]

I'm reliably informed that the throttle pot does little to control the ECU, other than to decide whether the engine is idling or not. Unless major changes have been made to the throtle, no adjustment is necessary. One function of the pot I was not aware of is to activate the cold start injector for additional enrichment when the throttle it opened quickly - a sort of electronic accelerator jet. Info from TopCats Racing who have just done a good job of sorting out some rough running and idle problems for me.

[dickymint]

2 sheds said:

dickymint said: 2 sheds said: There should be an idle adjustment screw facing down on top of and to one side of the throttle body, clockwise to decrease, if you tamper with the throttle lever you will need to reset the position sensor (potentiometer) this would be worth checking first anyway. 850 rpm is OK Tim All true but first check the butterfly gap is 0.002" when closed? correct me if im wrong please Tim. You are totally correct, but if the throttle stop hasn't been touched ?, just turning the by-pass screw alone might do it, then if it runs ok i would leave it at that, if setting up from scratch just ask and i'll post or email the full procedure. The 2 1/2 turn theory only works if the throttle butterfly is in the correct position, Tim

Tim,
Mines in garage about to have new camshaft fitted. I have to take up my Haines manual and Bible for him so your procedure would be useful, also if you got one for timing that would be great.
email if your not to busy.
Cheers,
Richard.
PS Hes changing the water hoses for the ones you sold me and is likely to contact you soon for the others.

[wedg1e]

gerry attrick said:

One function of the pot I was not aware of is to activate the cold start injector for additional enrichment when the throttle it opened quickly - a sort of electronic accelerator jet. Info from TopCats Racing who have just done a good job of sorting out some rough running and idle problems for me.

Sorry, that's poo (unless you have a hotwire system, in which case I'm probably talking bollocks as well!).
The only connection to the cold start injector (apart from the 12V feed) is from the thermotime switch: the ECU doesn't know anything about it.
As I say, this is flap meter talk...

Ian

[blue350i]

Thanks for the advice had a tamper on Saturday and now idles smoothly at about 850rpm

[zorro]

plewis66 said:

The idle adjustment is a hex grub screw (so an alan key is required). .

My 350 had a single-slot screw......guess they just used whatever they had lying around at the time