318i rough idles when hot only in park or neatral

[skinny2508]

I just bout this old rig its a 1985 318i when it first starts it runs alright untill I touch the throttle than the idle jumps between 500 and 1300 but only in park and neatral in gear its fine what could all the possible problems be ? Also there is a little sensor thing the bolts onto the side of the airbox that has a vacuum hose and an electrical wire coming from it that is smashed it bits what is this called ?? Sorry for sounding really stupid in advance first bmw haha

[Jaxx_]

The thing that is smashed to bits is probably the barometer sensor. It's a small thing attached to the air box.

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[thebutterson]

Most of the people here have/had idle issues. If you're new to l-jet m10's, I'll let you know the idle system sucks. Since yours seems to function in gear you can probably rule out air leaks. I noticed on the wiring diagram the automatics have some sort of input to the idle computer from the transmission range switch as well as a temperature switch. You might want to check those out.

If that doesn't work you can start swapping components or remove the system and adjust the throttle body stop so it will idle.

[Vtec?lol]

Most of the people here have/had idle issues. If you're new to l-jet m10's, I'll let you know the idle system sucks. Since yours seems to function in gear you can probably rule out air leaks. I noticed on the wiring diagram the automatics have some sort of input to the idle computer from the transmission range switch as well as a temperature switch. You might want to check those out.

If that doesn't work you can start swapping components or remove the system and adjust the throttle body stop so it will idle.

I wouldn't do that. Being a long time m10 owner here's my .02

Most cars will settle their idle under load with small vacuum leaks. Remove that airbox sensor and plug that vacuum line. Look for other leaks.

AND DO NOT ADJUST THE THROTTLE BODY STOP! Once you go down that route you'll more than likely get lost and never make it back home.

Once all the little air leaks are fixed the older jetronic does a fine job. Problem is, m10's are very prone to vac-leaks all over.