Help Idle missing backfires!

[Hawk]

Last night on my way home from work my car started backfireing randomly when I would clutch to shift or let off gas with clutch still engaged. Then about 3 mins later the idle was bouncing between 300-1500rpm and the backfireing was worse. The pipes were burning clean but the engine bay smelled of unburnt fuel. I checked to see if the Afm flap got stuck. And made sure there was no vaccum leaks (dipstick, oil cap , intake boots). When I put the Afm back on the backfireing went away but now the engine is missing all the way through the rev range and still wont idle. Its around 300rpm and rough with foot off throttle.

Any help would be greatly appreciated!

[DrMcDave]

Last night on my way home from work my car started backfireing randomly when I would clutch to shift or let off gas with clutch still engaged. Then about 3 mins later the idle was bouncing between 300-1500rpm and the backfireing was worse. The pipes were burning clean but the engine bay smelled of unburnt fuel. I checked to see if the Afm flap got stuck. And made sure there was no vaccum leaks (dipstick, oil cap , intake boots). When I put the Afm back on the backfireing went away but now the engine is missing all the way through the rev range and still wont idle. Its around 300rpm and rough with foot off throttle.

Any help would be greatly appreciated!

sorta of sounds like an electrical issue. plugs, wires, cap and rotor. if i recall you just replaced all that stuff right?

[Hawk]

Everything cept the plugs and wires and they only have 20k on them. And wires are jacobs so they should be good forever.

[NC325iC]

thats probly your problem, bmw has spark plug wires with resistors in them if you use wires without them aparently it doesnt work well

[jlevie]

Backfiring is going to be a case of the engine running too lean, spark timing too early, or a leakage of the intake valves. Figuring out which applies is a matter of eliminating possibilities.