is it possible to raise the idle on my E34 touring with the M50 motor?

[Boost Infection]

I have a non- vanos motor in my E34 touring and my idle sucks. It has been idling at 500-550 rpm and I get a rough idle. On my 3-series with the same m50 I get 750 rpm which is perfect. Is there a way I can raise the idle or is their something in the motor thats gone bad??

[Rigmaster]

there's no "adjustment" for the idle- if the idle is to high (or too low), then there's something amiss.

I would check for vacuum leaks in the Idle air control circuit, maybe a faulty ICV- Idle Control Valve..... (??)......

Sorry, I can't give you better advice- surely someone will come up with something..


Bret.

[Boost Infection]

Is the Idle air control vavle hard to change??

[George Davis]

Part of the idle air comes through a very small opening of the throttle plate, the rest is controlled by the idle valve. Poor idle can be caused by crud built up around the throttle plate, so just getting in there and cleaning out the crud may help. You may be able to just wipe it out, or use a bit of throttle body cleaner or brake cleaner plus rag.

[Rigmaster]

Is the Idle air control vavle hard to change??

Not hard to change, but it's not cheap, and I wouldn't recommend replacing it without having a good idea that it's the culprit......


Bret.

[Boost Infection]

Not hard to change, but it's not cheap, and I wouldn't recommend replacing it without having a good idea that it's the culprit......


Bret.

Thanks for the help guys

[gtopaul]

I have a non- vanos motor in my E34 touring and my idle sucks. It has been idling at 500-550 rpm and I get a rough idle. On my 3-series with the same m50 I get 750 rpm which is perfect. Is there a way I can raise the idle or is their something in the motor thats gone bad??

If the suggestions work let me know. My 92 touring does the exact same thing and idles about 550rpm. I've already swapped out the DME, MAS, and air filter with no change. Thinking about cleaning the throttle body and ICV but don't want to tackle that until I irder new ICV hoses. Seems like they always break for me when I try and remove them. The car idles solidly at 550rpm but just roughly.

Paul L

[infinity5]

If it idles soldily at a number, but roughly, could it be something else? like sparkplugs not firing or someting?

[SRR2]

Idle speed is set by software timers and the crystal-controlled clock generator in the ECU. It's a closed loop system, such that the ECU will drive the ICV to whatever duty cycle necessary to achieve the programmed setpoint. No amount of messing around with settings on the engine is going to change the idle speed, unless you screw it up so badly that it's out of the range of authority of the ICV, in which case, you probably will have other problems.

If it's really that serious a problem for you, try sweet-talking Mark D. I'm sure he could cook up a chip just for you that has whatever idle speed you fancy programmed into it. I wouldn't make any rash assumptions about its ability to pass smog testing however, so you might have to factor in a once-yearly reversion to the stock chip.

BTW, adaptive idle speed is one of the slick features I discovered BMW designed into the E39 and presumably other cars of that and more recent vintage. The ECU has inputs from more of the car systems than the E34, two of which are the state of battery charge and the realtime load on the electrical system. It uses these to increase idle speed in cases of low battery charge and/or high demand to raise alternator output as necessary.

[Boost Infection]

If it idles soldily at a number, but roughly, could it be something else? like sparkplugs not firing or someting?

Just changed plugs maybe my ICV or something not firing right