Expert: Josh Fields - 4/26/2006

Question
I have an 89 325i that barely idles, spews black smoke and coats the spark plugs with carbon. This all started when my daughter rear-ended her friends car.  It pushed the radiator into the water  pump, and locked up the water pump and fan clutch.  She drove it about a mile and the car died.  I have not gotten the body work done yet and cannot get the fan clutch on.

I have so far replaced the water pump, timing belt and tensioner, intake manifold gaskets, throttle body gasket, oil return tube o-rings, cleaned the ICV, adjusted the throttle position switch, checked for loose pipe connections on the throttle body, replaced the oil filler cap and dipstick, all vacuum hoses going to the charcoal canister, and brake assist. Replaced the injectors and fuel pressure regulator, performed all the tests at the ECU wiring harness specified in the Bently manual. Checked the crank position sensor, and timing marks for crank and cam are dead on. Adjusted the valve clearance, Replaced rotor and distributor.  Plug wires have only 30k miles on them.  New fuel filter and fuel lines.  Have not check fuel pressure or flow to specs, but used new fuel pressure regulator from bmw and flow seems good.

Compression test is within spec for cylinders 1-2-5-6.  3 is slightly low and 4 is slightly high  by a few pounds each.

As far as I can tell, my car does not have the infamous C191 connector.

Any ideas on where to look next?

Answer
Alan,
 Sorry for the late reply, it's finals week, and I've been studying heavily.

 You have replaced ALOT on this car, and there are only a few things that could be holding it back.  AFM (Air Flow Meter) on the end of the intake boot could have been damaged.  Its the silver box-like mechanism that is attached to the air filter box.  There is a TINY needle in it, that measures the temperature of the air, and this could be broken.  The There is also a flap that opens as more air is sucked into the engine.  As this flap opens it also rotates a contact that on a piece of printed circuit board.  As this flap opens it raises the voltage signal going to the ECU.  The AFM basically measures volume of air and it's temperature so the ECU can adjust fuel ammounts.