WOT car stops accelerating at 4k rpms and loses power, check engine light flashes

[scarecrow]

Hey guys. Weird problem with my 91 IX. When accelerating around 4k rpms the car feels like it hits a wall and stops accelerating. The check engine light flashes on and when you let off the gas the car drives fine again and the light turns off. Feels like the engine loses all power for a split second and sometimes there is a back fire out the exhaust. Car idles great and revs all the was to redline when not in gear.

This car did at one point have a millef maf conversion. For the conversion the MAF needs 12v running to it so there is some splicing that was done to the wire going to the AFM. THe car is now converted back to stock with a junkyard afm. Would the car do this if a signal was lost from the AFM? Did i not correctly re wire the harness connecting to the ecu? Ecu bad? Fuel problem?

what do you guys think?

[cabriodster87]

Exhaust backfire is due to loss of spark, raw fuel ignites inside the exhaust when spark comes back.

Check harness connections/ ground and main relay voltage. Thats all i can think of at the moment.

You may be loosing ECU funtions (Flashing CEL)

[scarecrow]

Thanks for the reply. I swapped in two different ecus and the problem still persist. Going to check grounds, harness and relays now. If you guys have anymore ideas or input let me know!

[redlightpete]

I had a bad coil that would cut out completely at full load for a couple seconds. I also had similar symptoms with a corroded C191(?) connector, the one under the intake manifold. If you haven't checked this connector, you might want to pull it apart and see if it is a big green mess.

[LJ851]

Crank position sensor. Don't buy an aftermarket one either, BMW or OEM only.