1995, 325i, E-36, 90K miles, Cold weather snap came to town, car surges from 500 rpm to 2000 rpm at idle in the "blue" temp zone, when warm it is super smooth at 700 rpm

Have changed thermostadt and temp sensors, no change. Air mass meter changed, but no difference

I am new to the forum but would appreciate any thoughts on where to go/look next.

First of all, is your check engine light on? If so then get the code read @ the nearest auto zone and look it up on the net. I think your problem is the idle control valve. I had a similar experience but my surging wasn't as drastic. The idle control valve is attached to the bottom of the intake manifold close to the throttle body. You can get one for pretty cheap($100) at alleurasianautoparts.com. Let me know if this helps.

I have a similer problem that is going on for 2 winters now!

When the temperature is below 7 C,the car starts with great difficulty or does not start at all.
The spark plugs gets dump with fuel.
If the temperature goes over 7C...all is OK!

Also,when in the highway,I have black smoke coming out from the exhaust at gear changes!!!

I have replaced almost everything!!!Idle Control Valve,sensor for water temp and air temp,spark plugs....NOTHING!

The reason seems to be a damaged fuel pressure regulator or something that drops the fuel pressure!
So in fuel mixture is very rich and gradually I get cloaked sparks that cannot burn the extra fuel that is sprayed during cold weather!

I would suggest that you chech the fuel pressure!
Not only when you turn the ignition to on,but also after 1 hour to see how fast the pressure is dropping!It may be that the regulator is OK but the sub-pressure hose is damaged and leaks!!!!

I wish you to find it!!

O2 sensor ? ? ?

Kouk, your problem is the E.C.M. Just had mine replaced...Was an intermittant full rich problem with the computer.Mine would run great some days and others would blow black smoke when getting on the highway. Seemed worse on really cold days. Hope this helps. Later, Mark.

Well...it was solved!

Mark EM, I had changed the ECU (DME,or what ever it is called!) and the problem remained!

I chacked the fuel pressure and it was 3.5 bar, flactuating eratically down to 2.3 bar!!! :eek:

I've changed that and also the sensor of the crank wheel and the wheel itself!!

It starts great now even at -2C (I am in Greece and that kind of temperatures are not common!)

The symtom I am having now is black smoke when changing gears but I assume that it is because of the chip I have istalled in the ECU!! :evillol: