New Engine Suddenly Running on 3 Cylinders

[bmwman91]

OK, so just after I fixed my lousy idle on my new motor (big vacuum leak), the car decides to run on 3 cylinders. I managed to limp home with it sounding like a Harley motorcycle to take a look at things. Prior to that, it was running great and I got a good ~80 miles on it.

Spark plug #2 was covered in carbon and wet with fuel. Plugging/unplugging the coil pack didn't seem to make much difference, whereas unplugging any of the other 3 seemed to cause a stall (with throttle held open, can't idle otherwise). Just to be sure, I swapped coils 2 & 3, and it seemed like it followed the coil, sort of. Anyway, I ran all over town and found a replacement coil (I am using a COP conversion) and replaced the suspected bad one. No improvement. I swapped spark plug #2 with a known good one from my old motor. No improvement.

So, I sort of have no idea what it could be. It seemed to  be an obvious spark issue since the plug was fouled and wet with fuel. That rules out a plugged injector I think. How about a stuck one? MM provided cleaned/rebuilt ones, so it seems unlikely. The failure seemed to follow one coil, although it was running so poorly that it was hard to tell, and a new one didn't help. Maybe a wire broke in the connector or something, or maybe the DME coil driver died. I am going to try picking up a spare DME and ignition parts from a local member tomorrow morning to swap that stuff on and see if it helps.

Any other ideas? This is really really getting old. At this point, I think that I need a boring, reliable daily driver of some sort, either in addition to, or as a replacement for this car. I have sunk far too much time and money into it, and I am tired of screwing with it only to have it frequently fail me at random times.

[DesktopDave]

Odd that all this is happening at once, isn't it?  Maybe it's just bad luck or coincidence?  

I'm betting on a single bad coil and potentially the related coil driver damage.  If it followed the coil it can't be a damaged wire in the harness.

[bigred]

The spark plug wire loom twist and turns several times on my engine.  A good way to wreck plug wires.  I waited until night, then sprayed the wires with water. Then started the engine for the light show.  You can hear and see the sparks jump.   Being cheap, I took the wires off and coated them with tire shine.   Still running fine!  But if you have an internal wire break, you can ohm them out.

[bmwman91]

Thanks for the input guys.

bigred, I have done a coil on plug conversion and no longer have the long ignition wires. The coils sit on the cylinder head right above the spark plugs.

Dave, it is hard to say exactly what is going on. The WBO2 sensor takes ~10 seconds to warm up fully, and when the car is misfiring, it will end up running a bit differently once that kicks in and reports a lousy exhaust gas mixture. My dad & I weren't taking that into account & pulling coil connectors shortly after re-starting it, but it SEEMED to follow one of the coils. Replacing it didn't help though, which is odd.

The next steps are to swap in a different DME and to do a compression test. The thing that I forgot to mention is that the engine runs very LOUD now. There is a ton ox exhaust noise, like combustion is taking place in the exhaust system. I think that it is unlikely, but maybe a valve crapped out? Even if that was the case, I would assume that there would still be partial ignition and I wouldn't have found a wet spark plug. Maybe since the exhaust was fully heated when [whatever] failed, the unignited air/fuel charge was being passed down the line to the catalytic converter and exploding. The thing is that the car sat for an hour while I went in search of an ignition coil but still made all the loud exhaust noise, so I don't necessarily think that the air/fuel was igniting in the cat.

Per a member on r3vlimited, the ignition driver ICs in the Motronic seem to poop out with some sort of regularity. I just don't know if a non-firing cylinder can lead to excessive exhaust noise. It would be nice if this was just a bunked ECU.


I am at sort of a loss as of now. This sort of looks like the end of my E30 days. In a way, I hope that there was a mechanical failure in the motor so that I can send it back and negotiate some sort of refund, sell the rolling chassis & old motor cheap and go get a car that I never have to do more than change the oil of. Even if this just turns out to be some electrical nonsense, I don't think that I can ever trust the car enough to take it out for more than errands within 50 miles of home, and them I am stuck with a very expensive grocery-getter. I am really regretting blowing all this money on the new motor when I should have sold the rolling chassis 4 months ago and bought something else. I thought that my fiancee was crazy to tell me to do that back then lol...I guess that I should know by now that she's usually right.

Sorry to be such a downer and all. It's just been too many hours of labor and too much money at this point and I don't know what else to do.

[DesktopDave]

A dead coil would fail to fire, as you see on the plug.  That'd mess up the O2 reading & absolutely cause backfiring in the manifold.  Did you double-check the cam timing?  I'd assume that MM would build first-class motors, but you never know.  Forgetting to torque a few loose bolts is all it takes.

As for the DME...the problems that I've seen isn't from the drivers, per  se.   It's from the lack of current protection.  If/when the coils  short internally, the driver FETs happily keep feeding them current  until they die.   Results are the same regardless.  Unfortunately, those  Darlington FETs are proprietary Bosch parts.  I'm considering salvaging  them from later M50 and M44 units on an exchange basis.  The EWS-II M44  DMEs are almost worthless, I picked one up for experiments.

I hear you on all that work...frustrating to see all this investment seemingly down the  toilet.  I suspect you're just burned out.  Let it sit for a few days so  you can forget the frustration a bit.  I usually have to do that three or four times when I get really annoyed with cars & bikes.  I'm usually so glad I did - I start thinking with an open mind again.  You're not behind the 8-ball.  You could likely recoup a lot of your money if you decide to drop the car.  Otherwise, just keep plugging away.  IMHO it'll absolutely repay itself ten times over.

[bmwman91]

Well, I found the problem. For the time being I am keeping details to myself since I have a lot of phone calls to make and I suspect that NOT making the issue public might be my only bargaining chip at this point. I regret to say it, but this signals my exit from the E30 community as I look for a red 4dr Jetta with a 5 speed. It's time for a car that I can trust, as heartbreaking as the thought of not owning an E30 is to me.

I'll keep you guys posted somehow or another, and I will of course still check/post on here. I think that the community is more important to me than the car at this point!

[keflaman]

I hear you on all that work...frustrating to see all this investment seemingly down the  toilet.  I suspect you're just burned out.  Let it sit for a few days so  you can forget the frustration a bit.  I usually have to do that three or four times when I get really annoyed with cars & bikes.  I'm usually so glad I did - I start thinking with an open mind again.  You're not behind the 8-ball.  You could likely recoup a lot of your money if you decide to drop the car.  Otherwise, just keep plugging away.  IMHO it'll absolutely repay itself ten times over.

I agree with Dave. You've come a long way since you decided to commit to this project and we're all rooting for you. You're an extremely intelligent guy and I/we have faith you'll figure it out.

Take a break, recharge and get back to basics.

[bmwman91]

IMHO it'll absolutely repay itself ten times over

I dunno man, $120k would be quite the pay-off lol. I think that getting a refund will suffice since it is enough to get me a nice used car.

[bmwman91]

I agree with Dave. You've come a long way since you decided to commit to this project and we're all rooting for you. You're an extremely intelligent guy and I/we have faith you'll figure it out.

Take a break, recharge and get back to basics.

Oh, there is zero mystery about what happened. This was the death-blow to my E30 enthusiasm and there is no way to recover from this in anything less than 3 weeks, and I have been car-less for close to 4 months already. It's done, I am sad to say. I appreciate the encouragement, and normally I would be receptive, but the situation is now in the "ridiculous" section of my book!

-----

Don't take this as some sort of covert knock on Metric Mechanic either. They have been very polite to me and great to talk to during the build. The issue I had this weekend may well just be one of those one-in-a-million things, and I do not hold it against them. Now, how they handle things in the following days will determine how much information I post across various forums about my experience. Based on prior interactions with them though, I think that everyone will reach an amicable agreement.

[doitover]

I don't know that I'd go from your e30 to a VW and hope for better reliability and access to cheap parts.

I understand your pain but read over all the times people mention regretting having sold their e30. It took me a year to get mine running to the point that I use it now for my daily driver.  I do expect it to break at any moment, but that is true for pretty much any 6 year old or more.

I'm pressured pretty much every day to sell mine for something new but I can't imagine anything else that I'd enjoy as much.

Besides, if you don't get it fixed, none of us will ever be able to get our wive's to approve a MM motor.

[bmwman91]

Haha yeah, I know deep-down that the "right" choice is a Civic or Corolla if I want a car that I never need to do more than change the oil on. My fiancee's 2003 Civic that she bought new in 2003 has about 170k miles on it...has only cost her $2500 in maintenance. $600 for a timing belt change (inc. labor) and ~$1900 for all new shocks & struts (inc. labor). I spend that on the E30 in a year, easy. A VW...parts aren't any less expensive, but the goal would to buy one that doesn't need them all the time. A few friends have Jettas with 100k miles on them and they have been totally trouble-free. They are turbocharged ones too. As much as I would like the power, I would probably avoid a turbo model since those always lead to costly repairs down the road.

I know that I will miss the E30, and probably have days where I regret parting with it. It is a great little car, and basically nothing newer than it has the same feel. At the same time though, I just can't drive a car that I can't trust anymore. Really, there has not been a single time that I started it in the last 2 years where I wondered if that was going to be the time that it was going to strand me (and it has a few times).

I sort of painted myself into a corner here. Ignoring core charges, the cost of the engine was $12k. It was a "make it or break it" decision when I did it. Unfortunately, it just isn't going to work out and that was all of my disposable cash. I now need that money back so that I can use it to get a newer, more reliable car. If I had a house and a garage to keep a shell, I might consider doing that and rebuilding the old M42, but I would have just done that in the first place if I had a garage. Instead, the broken car has been sitting in my parents' driveway for 4 months and I have a nice 20 mile bike ride whenever I need to go work on it (my apartment does not allow car projects lol). If I had just gone with a $3k rebuild locally or something, then I could consider just having it fixed. But, I am getting married in 2 months and have been totally neglecting that because of the car. I also do not want to impose on my parents any more than I already have been.

My priorities have shifted a lot in the last few years, and there isn't really room for an unreliable old German car. The thought of parting with it literally makes me cry; it is the exact same feeling I have had when I had to take aging pets to the veterinarian to be put to sleep. You really don't want to and it kills you to do it, but you know it is the only right choice. It is especially hard to part with it since it is the basis for my user name across many forums, I have made tons of friends through the E30 community and the car truly is responsible for my career in engineering in that it got me interested in mechanical stuff and drove me pretty deep into electrical engineering.

Now, there is one possible "happy outcome." My sister drives an E36 318iS. The engine is good, but the car itself is a piece of crap. I am considering giving her the chassis and helping her swap her engine into it. I think that I would just need to swap intake manifolds, right? I would much rather give the thing to a family member than sell it to a stranger. I am not sure where I will find the time to do this, but it would be worth it to me.

[wazzu70]

Bummer about the issues!

FWIW I have owned a few VWs and Audis, and all I can say is I would be embarassed to say I was an engineer for that company. Very poor quality in pretty much every aspect besides styling.

I sold my 2004 A4 Avant for a 2004 325i and could not be happier. The e46 is a great daily driver IMO. Just something to consider.


The engine management in the e36 318 is different. Not sure how easy you can swap one for the other, especially if you get rid of DSIA. The maps would be way off.

[doitover]

Selfish interest on my part, I spent some time this morning going over some of your how to articles this morning, sleep on it.

I had an 86 GTI and it was a nice car, BMW like in feel really, if BMW did FWD. That was about the last generation to have any soul. I guess I'm an anti safety kind of guy but that was about when all cars lost their soul.

Besides, I need for you to finish that MAF conversion kit.

[bmwman91]

Haha well, I am still planning to work on the MAF conversions. I'll keep you guys posted on that.

How is the reliability of the E46? They don't seem to get amazing mileage by any measure, but are they mostly hassle-free?

I agree that no new car has the same feel / soul to it that older German cars do. That will be sorely missed. Unfortunately, I can't deal with the other compromises that it seems to come with.

I talked to my father briefly, and we may try to keep the car in the family. I bet we can get the old M42 rebuilt for $1-2k to stock specs, doing much of the work ourselves. If he can convince my mom to have a non-running car sitting around for a few more months, that is..... I will just give it to him or my sister and let them pay registration & insurance. They will let me drive it from time to time I am sure.

[wazzu70]

A number of my friends have had e46s for years with no real issues. I have had mine for 6 months, bought it at 100k miles. All I do is put gas in it and change the oil. Its nice for a daily. Its no e30 but its still a nice driving car, its quiet, my wife does not complain about it being old, smelly, and noisy ect.

Something worth looking into at least.


I rebuilt my M42 doing a backyard refresh of sorts. Barely cost me anything and the car runs awesome. My track instructor even commented on how nice the car was.


Depending on your situation, work through the bugs and I am sure it will be solid for a long time. Assuming nothing mechanical is toast on the rebuild.