Running on 5 Cylinders when cold

[beamster]

My 1999 E46 323i 5 Speed with 140'000 Miles runs on 5 Cylinders when cold.
Once the Car warms up, i have to turn the Engine off, and restart it, and then it runs just fine. My Smog Guy's Code Reader says: Misfire on Cylinder No.3.
I have already changed the Ignition Coil, Spark Plug, Injector, on Cyl. No.3, and inspected the Ignition and Injection Harness, with no Luck. Next Thing would be the Main Electronic Control Unit, wich already has a Update on it. Since new Ones are expensive, i wanted to know, if someone of you Guys, have another Idea, Thanks a lot !

[Jeron]

Try swapping the #3 coil with another, ditto injectors. If you truly have eliminated plugs, coils and injectors then ECU would be my next try. On E36 cars bad solder on ECU boards was possible.

[beamster]

I swapped Injectors, Coils, and Plugs already, the Code stays the same.
I did not know about the solder Problems on BMW ECU's, Thanks !

[Manolito]

Jeron, is the bad solder problem owner-repairable? Where should I look for it? It can't be any harder than resoldering the surface-mount resistors in the radio, right? I have a '97 that has occasionally run on 5 cyl when cold, particularly after being parked for several days, for years. It has never set a code.

[beamster]

On a E46 the ECU is under a black Cover with 4 Allen Bolts, on the Driver Side upper Corner.
The new ECU Board look much more advanced, than on 80s German Cars.
I do not think, there is much you can solder on it, these days.
Mine looks perfect, perhaps it has a bad resistor on it, otherwise it would run on 5 Cylinders all the time, not just when it has been parked for a few days.

[Jeron]

There has been discussion of bad/cracked solder in the E36 forum in the last few years. From what I recall it was usually a cracked solder joint at the board where the ignition wire is attached. Thermal expansion causes the problem to be intermittent.

[beamster]

Since the 323i/328i Setup has been used in the early E46 also, could that be a problem on my 1999 E46 323i ? Thanks !

[Jeron]

I cant say. I don't think the problem is widespread. Most often it would simply be diagnosed as a bad ECU with no further thought give to why the ECU is bad.

It wouldn't hurt to take a look at the ECU board. Cracked solder may not be visible, but corrosion or water contamination would be..

http://forums.pelicanparts.com/showthread.php?p=4127634

[beamster]

My ECU Board looked like new, without corrosion etc. but i will check it again, where the Connectors are attached. Thanks !

[beamster]

I checked it again, everything looks fine, even the solder where the Connectors are attached, perhaps it has a bad resistor on it.

[beamster]

When the car does not run on 5 cylinder when cold, there is some kind of a valve ticking, sometimes for seconds, sometimes for minutes.

[Manolito]

Ticking can be an injector. They tick normally, but not loud enough so you can notice when they are working properly.

However, on this engine, I would presume that a ticking sound associated with dropping a cylinder was a symptom rather than a cause. Likely something ticking due to the periodic dip in vacuum caused by the dead cylinder.

On an American V-8, intermittent ticking associated with dropping a cylinder might be a collapsed hydraulic lifter that eventually pumped up and started working properly. I need to get out my Bentley's and look at this valve train to see if this could be something similar.

[beamster]

Thanks, the ticking on this Engine is pretty sure Valvetrain related.

[Jeron]

Valve tick, especially on cold start, is common. But I've haven't head of anyone with related misfires.

[beamster]

It is either heavy valveticking or misfiring, but never both at the same time.

[beamster]

I am probably donating the car to a charity, i never got lucky with BMW's.
The last one, a 92 automatic 525i had a bad tranny.