1986 323i Jetronic high and rough idle

[pbansal]

Ive been having an issue with my 323i for a while now its got a high idle of around 1-1200 but the idle itself is abit rough.
Ive replaced all the vac hoses, intake boot, spark plugs and disi cap but the idle is still lumpy. Weirdly the motor runs fine when its revd no missfires then its running silky smooth.
I have tried lowering the idle via the ICV screw which does lower it but it gets more lumpy as the revs get lower so ive left it to 1k where it seems about happyish.

Does anyone have any ideas on what it could be?

any help is appreciated thanks guys.

[flybynite]

Ive been having an issue with my 323i for a while now its got a high idle of around 1-1200 but the idle itself is abit rough.
Ive replaced all the vac hoses, intake boot, spark plugs and disi cap but the idle is still lumpy. Weirdly the motor runs fine when its revd no missfires then its running silky smooth.
I have tried lowering the idle via the ICV screw which does lower it but it gets more lumpy as the revs get lower so ive left it to 1k where it seems about happyish.
Does anyone have any ideas on what it could be?
any help is appreciated thanks guys.

Welcome to the fun of running a 323i

One thing to check is the throttle vacuum control (round disc thing with a pusher on the throttle. It holds it open until start then lets the throttle close to idle. Check it is not stuck. Check you can push it back against the aneroid or even better see if the idle revs drop if you unbolt it. Did you replace that tube too?

[pbansal]

Ive replaced the vacuum hose that goes to that and the arm does push out as it is revved

[flybynite]

Ive replaced the vacuum hose that goes to that and the arm does push out as it is revved

Then something is wrong because it is supposed to be out when the engine is off, holding the throttle open for starting. When the engine is started it pulls back allowing the throttle to close to idle.

It should not move when revved .

Unbolt it and see if it lets the throttle close to idle properly

[Tineca]

Mmm interesting for me too as mine had a high idle. Don't suppose you have a diagram of the item you are referring too?

[pbansal]

Ive replaced the vacuum hose that goes to that and the arm does push out as it is revved

Then something is wrong because it is supposed to be out when the engine is off, holding the throttle open for starting. When the engine is started it pulls back allowing the throttle to close to idle.

It should not move when revved .

Unbolt it and see if it lets the throttle close to idle properly

Is it not meant to do this?

[pbansal]

Just for reference this video was taken a couple years ago. It's abit better now but still about the same

[fixedwheelnut]

As Flybynite said check that vacuumn valve for leaks.

Also check the warm up valve if fitted, a lot of early jetronic ones had them, it provides extra air on warm up as the coolant warms up a thermostat style mechanism inside slowly closes it off, a lot of them seize up.

I don't think they are available anymore but I have seen VW K-Jetronic warm up valves retro fitted they just need an ignition feed and earth to work.

[pbansal]

As Flybynite said check that vacuumn valve for leaks.

Also check the warm up valve if fitted, a lot of early jetronic ones had them, it provides extra air on warm up as the coolant warms up a thermostat style mechanism inside slowly closes it off, a lot of them seize up.

I don't think they are available anymore but I have seen VW K-Jetronic warm up valves retro fitted they just need an ignition feed and earth to work.

Where Is the warm up valve? And what's the best way to check the valve is working?
Would this also be causing the rough idle?

[flybynite]

I am a big fan of originality, really am. BUT when they start going wrong the best thing that can be done with K jetronic is rip it out and run the car on motronic (just save the jetronic parts in a box for posterity)

That is what I will be doing on mine

[pbansal]

Has anyone had experience tuning the AFM?

Ive just seen a video on yt of someone tuning a L-jetronic system using a heathkit exhaust gas analyser to set the air/fuel ration.

Or does anyone know what exhaust gas analyser i can used to get a A/F ratio reading?

TIA

[fixedwheelnut]

As Flybynite said check that vacuumn valve for leaks.

Also check the warm up valve if fitted, a lot of early jetronic ones had them, it provides extra air on warm up as the coolant warms up a thermostat style mechanism inside slowly closes it off, a lot of them seize up.

I don't think they are available anymore but I have seen VW K-Jetronic warm up valves retro fitted they just need an ignition feed and earth to work.

Where Is the warm up valve? And what's the best way to check the valve is working?
Would this also be causing the rough idle?

Under the inlet manifold, see part 11 here.


https://www.realoem.com/bmw/enUS/showpa ... Id=13_0234