Re: Help!!!

["Ron Buchalski" <rbuchals@xxxxxxxxxxx>]

Kevin,

I'm not familiar with your car, but on other BMWs that I own, this type of 
problem could be caused by:

Bad or dirty idle control solonoid
Bad idle control module
Bad or mis-aligned throttle position sensor

My BMWs have an idle control solonoid that controls the amount of air sent 
to the engine when the throttle plates are closed.  When it works properly, 
it's constantly adjusting to control the amount of air admitted.  You can 
feel it "buzz".  If it's bad, it can stick in the wrong position and provide 
the wrong amount of air to the engine.

The electrical connections to this solonoid can also be intermittent, 
causing a similar problem.

The idle control module is the "brain" that controls the position of the 
idle control solonoid.  It receives input from the engine (temperature, rpm, 
throttle position), and adjusts the position of the solonoid accordingly.  
Obviously, if this is bad, you car won't be able to idle properly (of at 
all!).

Finally, the throttle position sensor provides an indication of the position 
for the throttle plates.  When they are closed, a contact closure is 
provided, which tells the idle control computer that the throttle plates are 
closed, and it should go into "idle" mode.

As you open the throttle plates, a variable resistance is provided to your 
car's engine computer, and it uses this resistance to determine how far open 
the throttle plates are.

At wide open throttle, another contact closure is provided, which tells the 
engine computer to go into WOT mode (usually ignoring the oxygen sensor, or 
trying to keep the fuel mixture proper for most fuel efficient operation.

A bad fuel pump would cause engine operation problems at all speeds, not 
just idle.

Way too much info, but hopefully it'll help you narrow down your problem.

- -rb

>
>Date: Sun, 7 Jan 2001 00:49:51 EST
>From: Kae2812@domain.elided
>Subject: Help!!!
>
>My Car Won't Stay On.
>Its an 86' 735i and tonight, when I was at my girlfriend's house, the car 
>kept stalling.  It would fire up as usual, but would cut off as soon as you 
>took the foot off the gas (in park).  I revved it up for a little while, 
>hoping the idle would straighten itself out, but it didn't.  It will stay 
>on as long as you give it gas and only have to keep it at 1000 rpm, but you 
>take your foot off, and down she goes.  Bad fuel pump, I have no idea.  
>Some thoughts or suggestions might help me and a mechanic save some time.  
>Or possibly, I could do it myself, I doubt it though.  I'm sure I'd have to 
>have it towed, I don't want to drive it like it is.
>Thanks in advance.
>Kevin
>CCA 191549

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