Rough Idle Help Identifying Function of Part

rba · #1 01-20-2009, 10:44 AM

I have been experiencing a rough idle the past month. I have tried a few things...clean Idle Control Valve....clean injectors...check for vaccum leaks. There is a part in the manifold that does some kind of air flow control. The part is called an "Adjuster Unit" and it is identified by part number 7 in the attached diagram. Does anyone know what the function of this unit is and what are the operating conditions? It has a rotating vane that closes off or enables more air in the manifold, but I am trying to understand how this finctions and what operating conditions control the operation.

Any help would be appreciated.
Thanks.

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lo_jack · #2 01-20-2009, 12:20 PM

That butterfly changes the length of the runners on the intake. It could effect idle, but is less likely than the other things you mentioned, or even spark and fueling problems at idle. When you take off the adjuster unit, what do you see in the intake manifold? Hint: it should not be oily.

rba · #3 01-20-2009, 02:54 PM

I have found a little more on the operation of the valve. If someone can tell me...at idle....is the valve open or closed? Also, at idle, is the solenoid that engages the valve energized or non energized.....+12 present or ground?

primetime · #4 01-20-2009, 03:21 PM

Perhaps you are getting bad fuel. You may wish to do a Techron treatment for the next the times you fill up with gas.. If it is bad fuel, that will eliminate the problem and your idle should return back to smooth.

rba · #5 01-20-2009, 03:35 PM

I tried something similar to Techrion. I have used Seafoam in the gas....no luck with that.

flyingmachine · #6 01-20-2009, 03:41 PM

any codes? tried cleaning MAF?

primetime · #7 01-20-2009, 03:55 PM

Quote:

Originally Posted by rba

I tried something similar to Techrion. I have used Seafoam in the gas....no luck with that.

How many times did you use it? It takes about 3 consecutive times when you fill up with gas for it to really do its job...

rba · #8 01-20-2009, 10:42 PM

Used it for two tank fulls. Should have done the job...thats about 850 miles driving.

Weasel · #9 01-20-2009, 11:18 PM

Quote:

Originally Posted by rba

I have found a little more on the operation of the valve. If someone can tell me...at idle....is the valve open or closed? Also, at idle, is the solenoid that engages the valve energized or non energized.....+12 present or ground?

Not many things on a BMW are 12 volt switched systems, so I wouldn't check ANYTHING but fuses with a test light...

But at idle it would be closed. It opens at higher rpms under load. You can easily remove it with 2 t-40 headded screws that hold it to the manifold for inspection. The only way it would really affect idle would be if the flap was broken, which only really happend if you have a decently bad intake pop from lean conditions.

rba · #10 01-21-2009, 10:35 AM

Thanks for your reply. That is what I thought. At idle it seems to be open..not closed. By open I mean the flap is in a horizontal position with the solenoid not energized. I will have to do a resistance test on the solenoid coil and the n do a test by trying to energize the coil to see if it operates.

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