I'm stumped... After running just fine for a couple of months since I bought it, my 1990 325i has developed an intermittent problem. It may run fine in the morning, but not in the evening - or vice-versa. It may be exacerbated by heat, altough I am not certain. When the problem manifests itself, it appears as if one of the cylinders is not firing - perhaps #1, since removing that wire doesn't seem to affect the engine at all when this problem is happening. So I replaced the spark plugs, distributor cap & rotor, after which the car ran fine for 2 days. But today the problem returned. The rough running happens all the way from idle to redline (but the car still idles) - and for all the world it almost sounds like an aircooled VW. I was thinking it could be the injector - at which point my expertise ends and I'll have to turn it in to a mechanic. If anybody has other ideas or things for me to try on, I would greatly appreciate it.
Thanks for chiming in... I have thought about the plug wires, but in addition to looking and feeling healthy enough, I'd think the problem would be even more intermittent than it is. I may have figured one more detail - it could be temperature related. Cool weather (morning and evenings) works fine, high temperatures (midday) it has the problem. I still haven't figured out where the fuel injector wires go in and how to remove & inspect them, but I'll try a little harder. Thanks for the suggestions!
Intermittent problems are always a hassle to diagnose. You'll need to track it down when it's doing it. I don't have my Bentley manual handy (you should have one for yourself if you own an E30 anyway), but checking voltage with a multimeter of the affected cylinder's fuel-injector plug should tell you if you're getting power to the fuel injector. I think the fuel injector wire harness is part of the main engine wiring harness so you'd need a wiring schematic to decipher what to check for continuity - the fuel injector wiring harness has plugs, which snap onto each injector. You have to release the spring clip to pull it off the injector. If you look at more than one, do one at a time, don't pull them all off and get them mixed up. Should be easy enough to check if you're getting spark through the plug wire, don't shock yourself. Hopefully you can isolate which part of the chain is the problem - good luck
Thanks for the suggestions... I've tried to identify the injector plugs (looking in the Haynes manual) but the pictures are just too small. And things look so cramped on the car itself... It's my understanding that you can unplug the injector connectors (and test the injector impedance/resistance) without removing them or the intake manifold, so I guess I'll have to go back and try again. I'll have to wait until it happens again though - what with this cool weather, it could be a few days.
The fuel injectors are fitted into the fuel rail, underneath the intake manifold, as you look at it from the passenger side of the engine bay. The pic link is from Pelican Parts - the length of small-dia. rubber tubing runs from the intake manifold forward to the round black thing, which is the fuel pressure regulator, and the fuel pressure regulator is attached to the fuel rail. The fuel rail is a long, black, rectangular box-shape. Part # 1 here they're calling the injection tube - that's the fuel rail. http://www.realoem.com/bmw/showparts.do?model=1113&mospid=47309&btnr=13_0267&hg=13&fg=15 The harness connectors for the fuel injectors have a metal spring clip. In all likelihood, you depress the metal spring with a 2-finger squeeze, and it should come straight off without too much force being required. Some BMW clips of that type require you to basically pry off the spring clip, but I think the ones for all E30 injectors are likely press-to-release.