Engine Performance problem
1979 Other BMW Models 6 cyl Two Wheel Drive Manual 216000 miles
I have a 1979 BMW 633csi that stumbles and smokes (dark gray) when cold. It idles around 900 rpm and sounds like it is missing. The problem is worst at part throttle, when the engine bucks and shakes the car significantly, but when accelerating it runs relatively smooth. When warming up, the car hits a point when it suddenly runs smooth and the idle jumps up to around 1800 rpm, from which it gradually decreases to about 1200 rpm. Sometimes it will start running smoothly like this, but revert momentarily to running poorly when I give it part throttle. I figure the high idle speed once it's running smooth is probably a separate issue from the cold running problem. I've replaced the mass airflow meter (with a used unit), the plugs, and distributer cap. I tested the fuel pressure, which remained within the 33-38 psi specifications, but started at the high end of the range and decreased suddenly by about 5 psi when the car got warm. The residual fuel pressure dropped very gradually (about a psi per minute). I've also put one batch of injector cleaner through it, but I don't know where to go from here. It's been getting horrible gas mileage (in the 10 mpg range) and I'd love to get this sorted out.
have the same problem?
Thursday, February 19th, 2009 AT 9:56 PM