Serious jerking and studdering at WOT

[Tyler325i]

So yesterday I was driving my car an I was gettin on the freeway and got a little happy with it and sank the pedal. When I did so it just started seriously jerk and studdering and miss firing and all that crazy nonsense. I am getting seriously frustrated because I can figure it out. If I give it about 50% throttle it's ok and with slowly climb in revs, anything over that with cause stumbling and hard checking and the check engine light flashes at me until I let off. I have a brand new O2 sensor (3 days old), tested the ICV and TPS and seem to be fine, new cap and rotor last month, tested the AFM, checked the fuses and even hooked launch OBD reader to scan it and it says no codes found. Can someone please help...

[DesertBMW]

I have the same problem sometimes. I replaced the cap, rotor wires, plugs, and it still does it. I will do the M5x swap on it so I don't care. M20 can be anoying

[jlevie]

When was the last time the fuel filter was changed? A clogged filter can do this as could a worn fuel pump.

[Tyler325i]

Fuel filter and pump were replaced about a year ago, but I have replaced my filter twice already so I'm goin to pick one up and check if that fixes it, and desertbmw I don't know how it would get to you but I have a second m54 if your want it lol quite the shipping though...

[Gregs///M]

How did you test your AFM? With an oscilloscope? Because there is no other way to test it. I'm going to say your AFM is bad if its still original.

I have experienced this and repaired this issue on several of mine and my customers cars simply by replacing the AFM.

[NV325i]

Check your crankshaft position sensor. Mine did the same thing and I found out that the wire had fallen down onto the alternator belt and wore through the outside coating and shorted it out.

[Kozworth]

A flashing cel would dennote a type A misfire. A worn afm carbon track will essentially "loose track" of what the afm is reading, and the car will run lean. I thought of a spark related issue, because if the spark is weak and cannot burn the af mixture at higher rpms (more spark demand at higher rpm) then you will get a weak burn and produce less power, aka a miss.

How old are all of your ignition components? I might have missed it, but you never stated the age of the plugs, wires, or coil themselves.

[Tyler325i]

Alright update: installed brand new Bosch 4 prongs today, and new fuel filter today and I'm going to take it for a run tomorrow, new Msd blaster 2, wires, m30 afm, and CPS installed about a year and a half ago when I completely rebuilt and stroked the motor. Motor has brand new everything ( or at least when I dropped it in) so I think I just built up a bunch of s@#% in the filter from the previous owner seriously neglecting everything in this car. When I took the filter out I poored it into a cup and the fuel turned a pretty sparkly silver then jet black. This is the third time now I have replaced it. Just rember kids not all fuel is equal!

[efficient]

update?

[Tyler325i]

On my way to work, drove like a dream, then I as I was about to pull into work it started to act up again, I tore apart the fuel pump and cleaned some of the lines, and now I hooked up my battery to the charger to see if that might help since my batter was pretty low... Whenever it starts to choke up my wideband just goes flat so I think it's a fuel delivery issue. I'm trying to see if maybe I'm not getting an efficent ammount of power

[Quinthirty]

Alright update: installed brand new Bosch 4 prongs today, and new fuel filter today and I'm going to take it for a run tomorrow, new Msd blaster 2, wires, m30 afm, and CPS installed about a year and a half ago when I completely rebuilt and stroked the motor. Motor has brand new everything ( or at least when I dropped it in) so I think I just built up a bunch of s@#% in the filter from the previous owner seriously neglecting everything in this car. When I took the filter out I poored it into a cup and the fuel turned a pretty sparkly silver then jet black. This is the third time now I have replaced it. Just rember kids not all fuel is equal!

Fuel tank maybe dirty.

[EREKSHUN]

Crank Position Sensor gave me the same problem.

[Tyler325i]

Cps is less than a year old but I was thinking that too... But I just put in my new inline fuel gauge and when I give it full throttle I'm dropping 15+ PSI... I orded a new fuel pump yesterday and it will be here tomorrow, also I'm going to clean out my fuel lines to and in the tank, another update here shortly. Still open to ideas, it's progressively getting worse

[Tyler325i]

Alright status update: I went to start it this morning, dead. Cranking but no fire an just left it for after work. Go my new TRE 255 LPH fuel pump installed tonight and found I had 0 spark so I replace my coil with another MSD Blaster 2 coil. Fired it up about 20 minutes ago and ran perfect. Took it for a test drive and broke loose 1st to 2nd and into 3rd. The e30 is back up and running with no power lag and or throttle hesitation