In Reply to: More idle & Cat Conv. posted by Patrick on June 17, 1999 at 10:18:54:
Have you checked the O2 sensor. I know that the injection system is in closed loop mode, bypassing the sensor when cold, and then goes into open loop and starts operating when the engin is warm. Could be some bad readings at the sensor that could be causing your idle fluctuations. I think there was a post once of adjusting the idle mixture by observing the voltage levels at the O2 sensor. It may have been an approximation, but probably a good one, especially if you don't have access to the right equipment.
: Back to the wonderful Idle problems of the 528e ('84). When my engine is WARM, the idle fluctuates cyclically between 750 and 500 rpm. Additionally, the car doesn't start well when warm and occasionally belches some black smoke when it finally starts (I usually have to touch the throttle a little to get it going) I have replaced wires, cap, rotor, checked the ICV etc, and replaced the majority of the vacuum/intake hoses. (I don't believe it is a vacuum problem anyway becuase the cold start is great and the idle is perfect until the engine is really warm).
: Here is the question...Is it more likely that I have a leaky injector or fuel over-pressure situation (I know it isn't a low pressure problem becuase I pinched the fuel return line and the car died instantly), or is it possible that a blocked cat. could cause the problem. The exhaust stinks and the protective steel casing around the cat fell off a month ago. I believe the cat is the original w/ 150,000 miles on it...Any help would be appreciated.