This is a message I posted to the Senior Six list, maybe someone here will find interest in it, too.
I think a few of you keep a M42 powered 318i in your stable of fine motorcars. I hope this helps at least one of you. We have one that my wife loves and I have developed somewhat different feelings for over the 4 or 5 years we have owned it. I made her get rid of her Toyota after changing the timing belt on it and realizing that my hands were too big to fit anywhere important around that engine. She wanted a rat bastard because she thinks they are adorable girl cars, I figured an E30 would be close enough and much more practical. We bought it in good condition with around 130k on it and it is around 190k now. I generally like the way it drives, although it is too small and noisy for long trips. It really makes me appreciate the torque and comfort of an M30 powered car. But it is quick handling and light feeling, good on gas and revs well considering the huge goofy flywheel BMW hung on it.
Unfortunately there had been an odd problem with the car for as long as I could remember. Anytime it was started warm, it would run like crap for a minute. Started fine, but the idle would degrade and if left alone it would stumble and stall. It could be kept running with some stabs of the gas, but it would try to die and could only be driven with lurchy stabs of full throttle. After the minute was up, just like clockwork, it would magically run fine. I tried everything I could think of to fix this problem. I replaced every sensor on the engine, and swapped out ECUs and AFMs. I played around with the fuel pump, and even resorted in desperation to the kluge of installing a little timed relay/resistor gizmo to fool the engine into richening up the mixture for a little while. It was activated by a button and would just about keep it from stalling but was far from a fix.
This problem was driving me crazy and making me despise the car, because I hate nothing more than a problem with no solution, especially one that it is in my face every single time I am in the car. And I knew that deep down it is a pretty damn good little car for what it is. It has been an otherwise excellent car for us, never needing anything other than normal maintenance and service. And I never wanted to have to put a bunch of time into the car, I have plenty of projects for fun wrenching. I just replaced the original clutch last weekend, due to a howling throwout bearing. At the same time I replaced a bunch of little things in the drivetrain while I was in there, and gave the engine a good cleaning and partial resealing to cure some oil leaks from a ham-fisted warranty service way back before we owned it.(This was from the infamous profile gasket issue. I had previously obtained a Time-Sert set because they had managed to strip out a number of valve cover bolts apparently at the same time) I also had what seem to be the original starter and alternator rebuilt while they were out, there is a good shop about a mile from my house that turned them around inside one day for me.
I also found some bolts in the lower oil pan which turns out to be a common and occasionally fatal problem with these engines, the upper oil pan has a few bolts that are only accessible with the lower pan removed, and the oil pump pickup is secured to this area of the upper pan. So if the bolt dropping gets too far along, the oil pump can suck air. I caught it early enough and didn’t have any damage as a result, so I just gave everything a very thorough cleaning and threadlocked all the little bastards back in good. So if you have never had that lower pan off, it is easy to drop and well worth the time and trouble to check.
As to the warm start issue, I didn’t like the car enough to devote any more random time and money to a problem that seemed incurable, short of a Megasquirt or TEC-3R or something. And while I have both such items available they are a huge waste and a PITA for what is just a commuter car for my wife when she is working locally. So I just developed a bitter funk about the car and my wife likes the car enough that the quirk didn’t even seem to bother her. I had done some poking around the internet looking for a solution, thinking that it has to be something stupid and simple. I found an M42 forum, and it turns out that the problem has been plaguing a considerable number of E30 318i owners, with no solutions yet found. Until this past week.
Some guy discovered a connector in the wiring harness, noted somewhere in a BMW technical manual, that has something to do with CO, the cat, and the idle speed potentiometer, that needs to be disconnected to solve the problem. I don’t know nor do I care exactly what it does, only that it works. I noticed this post on Thursday night, very late, while it was raining. And I grabbed a flashlight and ran out in the rain and ripped of the harness cover and yanked apart that little connector. Problem solved. So apparently that connector is not supposed to be connected in the first place. I don’t know how or why it was connected on our car, but from the number of people on the forum with the same problem it is far from unheard of. Unfortunately these are relatively rare cars, with the M42 being installed in the E30 only for the last year or so of full production. So the documentation on these cars is thin compared to most other BMWs. Once again the internet saves the day.
I can now appreciate the car for what it is without the slow burn of a frustrated mechanic to taint the experience. And I like that M42 engine, despite the quirks of the profile gasket, which was solved early on, and the loose bolts, which are far from unheard of in many BMW engines, including our beloved M30s.
M42 E30 318i sucks no more
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adrian in florida
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Karl Heinz
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Kyle in NO
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