1993 318i E36 M42 Engine Rough Idle
Looking through the forum I've found a lot of people with a similar problem, but I've never found any clear cut answers to my specific problem. My car idles at the correct RPM, (between 700 and 900RPM) but it runs rough. It sounds like I'm tapping the pedal every half second or so. Another problem, which may or may not be related, is that I have to give it a little gas to start the car. I'm also getting below average gas mileage, around 18-19mpg city, and I've been driving very conservative.
So far, as other threads have suggested, I've cleaned the Idle Control Valve with carburetor cleaner and sprayed it with WD-40. This had no affect on the idle and I've done this several times. A man at an auto parts store told me that lots of people clean those valves, but that it actually only solves the problem for a short time and they need to be replaced. In my case it didn't solve anything. I'm waiting to replace it until I know that it's even part of the problem. I've checked for vacuum leaks and have found none. All of the hoses are crack free as well. I've been told that if you do have a vacuum leak your car will most likely idle at a higher RPM. This is not the case. Other things that I've done which are probably unrelated to this issue include replacing the air filter and an oil change. I'm looking into the ECU, O2 sensors, Idle Control Valve, and Mass Air Flow Sensor as possible culprits to this problem. I don't want to drop another grand on this car like I already did with the AC, but that may be what I need to solve the problem. Please enlighten me if you know how to fix this.