In Reply to: Re: 535i(E34)Surging idle & miss @ hard accele posted by Richard on January 29, 2000 at 11:36:48:
: : HELP! I am a BMW rookie. Have owned the car for 60 days. 1989 535i E34. It recently started surging at idle and has even cut off on several occasions. Also it misses during hard acceleration to the point were you can see the drop on the tach. Are the problems related? Any ideas?
: Are you sure that it's a miss? or does it feel like a slight hesitation, almost like flat spots?
: The idle is most likely your Idle Valve. It is either bad or dirty. Turn the ignition key to where you see your dash idiot lights come on(not the start position) & go see if you can hear/feel the Idle valve hum. This is the black & silver devise that is just in front of the Throttle Body, about 1 1/2" dia with an electrical connector on the end toward the firewall. If it's not humming, it's bad or your connection is bad. Try cleaning the connection first. If it hums, remove it & clean out all the black carbon with throttle body cleaner, to where it will move freely. If it doesn't hum, replace it.
: Let me know about the miss/hesitation. I have a hesitation problem on my '92 E34 (535i), more so when it's cold. You can fell it accelerate, level off for a split second, accelerate, level off, accelerate, etc. I'm still trying to find the culprit on this one. It almost feels like a fuel pressure problem
Another easy test of the idle control valve, is to turn on the air at idle. One function of the idle control valve is detect engine loads at idle and send the signal to the Engine Management Control computer. If the idle doesn't kick up with the air on, the little valve is probably not humming ...