My car is a 1990 325i. I went to start it this morning, turned it over and it idled for about 3 seconds and died. I started it again and it ran, but it was low and grumbling. It was slightly erratic (anywhere from 400-800 rpm's). The most noticeable aspect was the low rumbling sounding rev and the increased vibration in the car. I tried revving it up and the car was very unresponsive; after holding the throttle halfway down it took about 4 seconds for the engine to reach 2000rpm. It seem underpowered as I had to give it a lot of gas (~2000) when letting the clutch out so it wouldn't kill. Also, the exhaust is extremely rich. To me it points to one or more cylinders not working, but I need help diagnosing what's causing the effect. Two days ago I drove it about 60 miles and it ran smoothly, and it hadn't ran since then. I don't think it's water in the tank, I've always had good luck w/ BP 92. It's been babied, also: it has new spark plugs, dist. cap/rotor, fuel filter, oil/oil filter, water pump, thermostat, timing belt, etc... If you have any questions or comments they would be greatly appreciated. Thanks, Bob
Does it still do it when warmed up or only when cold? I've had a bad idle ever since I bought the car 3 years ago and just could not for the life of me fix it, despite everything that I've done to it. At this point it doesn't matter, but it could be any number of things such as a vacuum leak, bad idle control valve (don't know if you have one being a later E30), in some rare cases a bad ECU, or some other things I can't quite remember right now. Start by checking for vacuum leaks I guess...
IIRC, a big vacuum leak forces the computer to dump lots of fuel into the system, so you end up rich. The biggest vacuum leak usually comes from the intake boot, especially if it's never been changed. Squeeze it and move it around while the engine's running. If the engine speed changes (either faster or slower), then you've found your culprit.
That is exactly the problem I have now. Runs like a champ in the warm weather, but once cold sets in, the idle is just horrendous if you try to use it immediately. I start the car, and it idles fine, but if I tap the throttle and let go, the idle is atrocious, and will stall if I don't keep the revs up. Since I don't like to waste fuel by letting the car sit warming up, I drive it, so for the first 1-2 minutes, I have to keep a part of my foot on the throttle while pulling to a stop and waiting for a light. Once I reach the onramp to the highway, it's fine, but if I don't want to keep my foot on the throttle at a stoplight, then I have to let off it very slightly and very incrementally until I have the engine turning over at normal idle speed, at which point I could let go. It's highly irritating, especially when I'm in a rush to get to work and hit almost every light on the way to the highway onramp. I can only imagine what people must think when I arrive at a stoplight doing about 1500-2000 RPM trying to keep it from stalling, and coming to a stop as though I was a 16-year-old trying to drive for the first time (with me giving priority to keeping it from stalling instead of braking smoothly). I've replacing everything you can possibly imagine related to idle and it still won't idle properly. Jeez. The joys of E30 ownership.
It is not my thermostat. It idled like this even previous to my cooling system refresh not even a year ago, and this included a thermostat. Besides, if you turn the heater on only slightly in my car, your clothes will be drenched in sweat! A smoke test revealed no leaks in the vacuum system. Both the Idle Control Module and Idle Control Valve both have been replaced, and some other stuff I can't remember.
Try replacing your thermo-time switch. I have a 1985 325e and had significant problems with the idling and surging. Replaced my thermo-time switch and it runs like a charm. I could not imagine that a sensor could cause so many problems. David
Well I parked it in the heated garage overnight (I live in Minnesota). I took out the spark plugs and cleaned them off; they were black as expected. I started it up and the idle fluctuated a little bit, but after a minute or so it idled fine. Then I took it for a spin and warmed it up and it was still fine.... uff. I have a hunch it's still running a little rich though. I'll have to let it cool down outside and see how it starts then.
