Hey guys - I'm new to this forum, but my 1996 Z3 has been acting weird lately and I could really use some help. I know the M44 rough idle thing has been beaten to death, but I spent close to 10 hrs searching the forums and checking for leaks, sensors, codes, fuel trims, and I can't put my finger on it. Here's what's happening: My car has developed a random misfire P0301 and P0300 (pending for weeks and no CEL), and is especially prevalent when the engine is cold. I cleared the codes and rescanned, and they both disappear, but if I scan when I can really feel the misfire, I get the same 2 codes. When I drive or rev the engine, I notice no irregularities and the car pulls and runs well. The bulk of the misfire is felt at idle (<900 RPM) and when cold (although you feel an occasional misfire at idle when at operating temp). Here is my exhaust noise about 2 min after starting the car cold in the morning:
http://youtu.be/VMcmoEUsBKc My RPMs tend to be pretty steady, except for a rare, minor idle hunt (usually felt when the engine misfires at a stoplight or something). The idle hunts a little bit when coming to a stop, but then steadies out. There is a larger hunt when I reverse and move (no hunt when the car is stationary in reverse). Here's what I know so far: -Smoke test revealed a very very very small vacuum leak from under the screw that keeps the CCV in place on the back of the intake manifold. I don't think that would cause this much of a rough idle (please correct me if I'm wrong). -Dry Compression on all 4 cylinders is close to 195psi. -Coolant temp sensor was replaced yesterday because I had one sitting around. -Unplugging the MAF did not help with anything. -IACV was cleaned yesterday...doesn't appear to be causing any problems. -Fuel pressure seems low at the head of the rail (I was reading 35PSI) so I changed the fuel pump which brought the pressure to about 42ish, but it was 37 when I started it. Got to 42ish by giving it a little rev. I had 3 different other heads examine the problem and no one can pinpoint it. The engine is clearly misfiring at idle, so it isn't just a light M44 lumpy idle. I'm thinking this is a fuel delivery problem because of the nature of the misfire only at idle, where fuel pressure is relatively small. However, would these symptoms be caused by a faulty fuel pressure regulator or bad camshaft position sensor? I'm really at a loss so I was hoping someone more familiar with the M44 could help me out. I really appreciate it.
96 Z3 Rough Idle 
Linear Mode
