2008 bmw 328XI N51 Hard Acceleration causes Multiple Misfire. I'm suicidal over this

[petes1997bmwz3]

I have a bmw 328xi N51 with 38k on the engine and 142k on the body. The engine was replaced. When you hit the gas hard it develops a p0300 code. I checked for vacumm leak and no leak. I sprayed down th engine with starting fluid and watched the fuel trims on my computer for any changes and none. I already replaced the valve cover from BMW and no vacuum suction when oil cap open. Vanos solenoids replaced, inside disa valve replaced , the ccv hose replaced from BMW, no cracks on intake boot either. I'm stumped. Again, only when you floor the car it hesitates and triggers multiple misfire. Idles fine all day and night. Fuel trims are good. Any ideas before I drive into the lake

[bms5]

I have a bmw 328xi N51 with 38k on the engine and 142k on the body. The engine was replaced. When you hit the gas hard it develops a p0300 code. I checked for vacumm leak and no leak. I sprayed down th engine with starting fluid and watched the fuel trims on my computer for any changes and none. I already replaced the valve cover from BMW and no vacuum suction when oil cap open. Vanos solenoids replaced, inside disa valve replaced , the ccv hose replaced from BMW, no cracks on intake boot either. I'm stumped. Again, only when you floor the car it hesitates and triggers multiple misfire. Idles fine all day and night. Fuel trims are good. Any ideas before I drive into the lake

I would suspect a failing air mass meter. When the problem is that momentary, it may not show on the fuel trims but it is going too lean which sets the misfire code.


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[petes1997bmwz3]

I will try and clean it first and test drive it and see what happens. Thanks for the response

[petes1997bmwz3]

New Mass Air Flow sensor didnt fix it. Back to square one

[jeff91121]

Coil packs maybe? Do you know what cylinders are misfiring? If so, can you change coil packs from a cylinder that is misfiring to one that isn't and see if the misfire follows the coil pack?

[Turbo2Pete]

My 2011 328i did the same thing, would run fine as long as you didn't get too aggressive... it was the #6 coil, that finally failed and it would misfire constantly.

#5 went a month later.

Check codes, if it's only on one cylinder, swap that coil with another and see if the code follows.

I also found the spark plug ground electrodes were well burnt - which increases the load on the coil packs, and may be part of the problem.

[Old525i]

Make sure the spark plugs gaps are set to 0.044 inches ... in all 6 plugs. Even if you bought them pre-gaped. In my experience, NGKs wear the electrode faster than BMW or Bosch plugs. Your mileage may vary.

[jclausen]

No fault codes or check engine light? Loose ground cables on valve over bolts or faulty valve tronic sensor?