Euro 318i - Hesitation, running rich, backfire

[Hokori]

Hi folks.

The car in question is a 1992 e36 318i with an M40 engine (European). Motronic 1.3.

Problems;

The car runs rich. I can clearly smell unburnt fuel at the exhaust. There's also a distinct "pop" sound that repeats itself continuously. I believe this is unburnt fuel igniting in the exhaust pipe.

The car hesitates for a few seconds when put under load. Doesn't matter if I accelerate smoothly or hard, same thing happens. It's usually more noticeable on low RPM's (up to 2500 or so). After that it pulls pretty good, but lacks power. (then again, it *is* a 318. )

Also, the oil smells like gasoline... When I noticed this I immediately thought about worn rings letting gas seep through to the pan. However, after I did a compression test, the numbers where 175 across the board.


What I've done so far;

I scanned the car for codes. Didn't pull out anything.
Compression test turned out good at 175 psi on all cylinders.
I checked for vacuum leaks, didn't find any. Replaced all vacuum hoses anyway.
Checked the fuel pressure regulator. I applied a manual vacuum to it, and it didn't squirt out any gasoline. I hope it's safe to assume it's alright, then?



I replaced a few items. Not with solving the problem in mind, more because it's about time. Miscellaneous things I replaced;

Fuel pump & level sender
Fuel filer
Oil + oil filter
Air filter
Plugs and plug wires
Rotor and cap



Now...as I see it, this leaves me with 3 options. AFM (air flow meter), TPS (throttle position sensor) or leaky injectors.

I'll be measuring the TPS electrical resistance tonight when I'm home. However, I doubt that a defective TPS would cause me so much drama.
I'll pull out the injectors tonight, and have them cleaned and tested tomorrow. Probably a good idea to do this anyway, for maintenance.

Which leaves me with the AFM...the problem here, is that I don't know of any tests (short of just replacing it) to determine if it's faulty. If I pull out it's connector, the car runs horrible and wants to die (so do I). There aren't many BMW's running around on this island, so sourcing a used AFM isn't possible (believe me, I've tried...and still am!). I would hate to buy a new (expensive!) AFM just so it turns out to be another problem.

So...does anyone have any ideas suggestions?

Thanks in advance!