wtf is going on w/ my car?

[Quik325ix]

Ok guys the dealership is stumped by this one too...when at full throttle in 2-5th gears my engine will cut off momentarily around 3700 RPM. Its like the fuel is cut off for a second or like im reaching the rev limiter... Ive checked the master relay and the fuel pump relay, changed fuel filter, plugs, battery, but still no help...the diagnostic said that it was the relays, but like i said no dice...what do you think...please respond before i start sinking a shit load of money into this problem...thanks guys!!

[asubimmer]

crank sensor?

[Quik325ix]

possibly...but dont you think that would affect it in first gear as well?

[asubimmer]

it should but they are weird things when they go out...they will come and go for a while before they totally die. So idk just a thought

[Febi Guibo]

if it's only happening at full throttle, I'm guessing your AFM... if you can, try swapping a known working AFM in and see if there's any difference.

[Quik325ix]

alright...maybe this would be a goodtime to put an m30 AFM in...how do i do the M30 AFM swap???

[SpunkyE30nOk]

you have to get an m30 afm that the serial number ends in "027" and thens plug and play, I've heard the rubber boot can be a bitch goin on but thats it

[EWAustin]

ooh ooh ooh, this sounds EXACTLY like what my 325is is doing...

What have you tried? what worked? what didn't?

I've got an extra M30 afm laying around, I'm gonna have to go see if it ends in 027. (edit: just checked, it ends in 019)

[Quik325ix]

ive tried the master relay, fuel pump relay, battery, a shit ton of injector cleaner, new plugs, cleaning the K & N and to no avail....

[EWAustin]

Does anyone know anything about the DME programming? Does it switch maps at 3700 or something?

What changes in the way the engine runs between 3600rpm and 3800rpm.

C'Mon, I know somebody knows this answer. I'm gonna go PM Jordan...

[PeaveyBassist]

If you have a multimeter you can also measure the AFM. I believe its terminals one and 2. As the door in the afm opens more, resistance should change. Example of a good one...

Closed - 2200 ohms
Half open - 3100 ohms
Full Open (WOT) - 4000 ohms

Example of a bad one...

Closed - 2200 ohms
Half Open - 3100 ohms
Full open (WOT) - 2800 ohms

The bad one would mean that the engine at WOT would be running real lean. It thinks its taking in less air like its under less of a load than it actually is. I would measure the AFM before you go spending money on it.

Will

[EWAustin]

I will measure mine tomorrow, but I'm hesitant to think that would cause this problem. Why would it only be at 3700rpm and why only under hard acceleration? And why never in first gear?

[Ball325]

crank sensor had the same problem only at 5500rpm and it was completely intermitten it would do it most of the time and than stop and then come back.

[EWAustin]

update:
it appears to be an ignition cut only.

Today I just happened to shift right as it happened, and it was as if the engine was shut off for a split second. Then, there was a loud BANG out the exhaust and the engine came back to life. So it seems that the fuel injectors are still firing, but the spark plugs are not.
Sunday I'm gonna check the cap and rotor.

[Quik325ix]

yea mine has done that a few times too...but i just thought that it was just excess fuel igniting after the motor came back to life...please update on what you find...thanks bro