What could it be? (Bogging down under acceleration, incline)

[iwanttobecold]

Hello, all...

Just did the mess under the intake. Successfully got her back up and running and now... Still a little rough on idle, but once I get it in gear, I can tell there's definitely a better fuel response. However, it's still bogging down under acceleration, mostly in low RPMs.

In the past 3 months I have replaced: spark plugs, air intake tube, fuel rail, fuel pump, fuel filter, fuel hoses, vacuum hoses, coolant hoses, tested/replaced faulty ignition coil; and cleaned out ICV, MAF, and throttle body using MAF sensor cleaner.

I don't really think this could be transmission-related, but at this point, I have to ask: could it? I don't know what else intake related I could possibly replace besides the throttle cable... The main issue is the car shaking (I had assumed misfire and so did a BMW tech), bogging down, as in low RPM range for that gear, accelerating on an incline or heavily.

Ex: Driving in 3rd gear, try to punch it and accelerate. If I'm on flat ground, it will possibly accelerate without bogging down. On any incline, however, it will bog down every single time. Also, if I was in the 1500 RPM range in 3rd gear and tried to accelerate, it would also do this until I give it the right amount of fuel (letting off) or just accelerating until it 'catches up'.

I can list more parts that I've replaced as I remember them, but it's important I figure this out before I move cross country this summer with it!

[maxeastman]

I am also interested in getting this diagnosed. Just picked up a vert with the EXACT symptoms. From what I have researched so far, I have decided it is probably the AFM. Going to crack it open to adjust the sweeper arm to make contact with fresh meat on the carbon strip.

check out this link if you haven't already: https://www.r3vlimited.com/board/showthread.php?t=247831

Let me know if you resolve this another way and I will do the same.

[DesktopDave]

Be sure there isn't any water in the DME. They can flood on the E36 in particular. The E30 is a lot better with water resistance. I had some occasional problems with misfires. When I bought it, the motor had a bit of oil in the spark plug wells.

Recently, the car was running really rough on cold starts. I pulled the plugs and found I had water in cyl #1. Not coolant, not oil, not raw fuel...it was plain water. I haven't been driving it enough recently, so my guess is that water condensed into the fuel tank, settled to the bottom and was eventually pumped into the motor due to the 15% alcohol mix we get around here.

I'm not sure this is relevant, but another thing I've seen is a lot of of M42 DMEs with burned-out coil drivers. I'd be especially diligent checking this if a coil failed. My guess is that the problem is caused by voltage spikes. These coil driver transistors (Darlingtons) can switch a lot of current but are pretty sensitive to voltage spikes. If a coil pack failed with an internal short between the primary side and the floating ground, the resulting voltage would shunt the coil driver when it grounded the circuit. I'd also guess the early 1.7 Motronic COP setups are less durable than later ones. There does seem to be a lot of complaints about cold solder joints and scorched transistors out there for many BMW models.

As for solutions, some owners have soldered new & used coil drivers into the DME. The M42 appears to use the same proprietary Bosch coil driver transistors as the early M50 and M60, among others.

Here's some other threads about that:
http://www.m42club.com/forum/index.php?topic=19079.0
http://www.318ti.org/forum/showthread.php?t=37901