Hi everybody!

For the past few months I have had a rough or low, sporadic idle on my 1990 740GL with regina. It sounds like there is a slight miss at idle when standing next to the exhaust pipe. It has a hard pulsing sound to it. The car runs great at speed and still gets 26 mpg. No abnormal smoke out of the tailpipe. Occasionally when you are on the interstate and go to accelerate a slight bit more, the car will hesitate 3 or three times very quickly. Other than that it runs great at speed.

At idle, sometimes it starts fine and idles initially at 1000rpms before settling down to around 800 rpms. Other times it will die as soon as you start it until you give it some gas to keep it running. It will run very rough for a few seconds before smoothing out, but still only idles around 500 rpms. While it is running at 500 rpms, it will still sound like it is missing if you stand by the exhaust pipe. Other days, it will idle around 1000rpms, but still sounds like it is missing.

I have replaced: IAC valve, ECT sensor, MAP sensor, Intake air temp sensor, O2 sensor(NTK # 25002), spark plugs, timing belt.

I recently took it through emissions and the Hydrocarbons reading was 900 (limit is 220) with a CO reading of 0.5(limit is 1.2). This would indicate that it is running lean, correct?

I've pulled a couple of spark plugs and they are grayish white on the electrode area with black carbon marks on the base of the metal threaded area. This points to a lean condition too.

My question is: Can a slowly failing fuel pump cause this condition? Maybe its running at about 40 psi instead of 43.5psi, which would cause these erratic symptoms?

I have pulled the vaccuum line off of the FPR, and there is no fuel leakage.

The car has no fault codes other than the normal 3-2-1 for the cold start valve fix.

Thank You,
Ben