New turbo, rough idle, and misfires

[Sliiiiick]

2011 N55 135i with upgraded fmic, chargepipe, catless downpipe, intake, oil cooler, fuel-it LPFP, colder plugs, JB4 map 5 running 93

Decided to try out adding MHD back-end flash using map 98GOB_Pump_USA and acceleration was much smoother, no codes no issues

Then I recently swapped the turbo to Vargas stage 1 and replaced water pump, thermostat, belt, and pulleys for good measure

Took the car to the track to test drive where it started to over boost (22 psi), misfire, and eventually went into limp mode and showed codes:

28A0 - Air mass system, calculated air volumes in air intake system implausible
2C56 - charging pressure control, pressure too high
2C58 - charging pressure control, switch-off as consequential reaction
2EE0 - combustion misfires, several cylinders
2EED - combustion misfires, cylinder 4
2EFE - combustion misfires, damaging to several cylinders
2F02 - combustion misfires, cylinder 4
300F - exhaust camshaft sensor, electrical short circuit to ground

The car now idles very rough where it will almost stall out below 500 rpm then goes up to 1,500 rpm back and forth.

Being no stranger to n55 misfires when most times its coils or plugs, I swapped the coils around to see if the problem was specific to cylinder 4.
Car continued to exhibit rough idle so I decided to get precision coils and brisk racing plugs (gapped to .020) with hopes of solving the problem. I updated the MHD tune to reflect the new coils.
Now I'm getting 30F2 code which is super knock sensor in cylinder 6 and rough idle still persists

I'm looking for some guidance and assistance to get back on the track!
Thank you fellow members!

[WilsoN55]

Are you running a stock MAF? probably time for a 3.5bar sensor.

Did you clear the codes and they're coming right back?
Camshaft sensor next.

[drwillb]

Check all your electrical connectors: camshaft, fuel pressure sender, LPFP, TMAP, VVT

[Sliiiiick]

I tried deleting the codes, but the super knock on cylinder 6 keeps coming up at start and idle, followed by hesitations and misfires

I didn’t think about upgrading the MAF sensor to 3.5bar, thanks for the idea!

I will start to check the sensors mentioned but most likely won’t check the camshaft sensor because it’s a PITA and car has no issues starting up

Could it be related to injector, MHD tune, boost solenoid, bad fuel, or incorrect gap in the spark plug?

Thanks, keep it coming!

[ErvGotti]

Originally Posted by Sliiiiick

I tried deleting the codes, but the super knock on cylinder 6 keeps coming up at start and idle, followed by hesitations and misfires

I didn’t think about upgrading the MAF sensor to 3.5bar, thanks for the idea!

I will start to check the sensors mentioned but most likely won’t check the camshaft sensor because it’s a PITA and car has no issues starting up

Could it be related to injector, MHD tune, boost solenoid, bad fuel, or incorrect gap in the spark plug?

Thanks, keep it coming!

The super knock code can be due to a worn out DMFW. The way you can troubleshoot this is by desensitizing your knock sensor with MHD. If you no longer get the code after multiple pulls, then it is more than likely your flywheel. There's a couple of old threads on E90 post about this, the DMFW when worn vibrates at the frequency that trips the knock sensor, especially once you start to add power.

This was the case for me, I switched to the Tuner lightweight flywheel and put my knock sensor back to normal and haven't had problems since. I have an N54.

Also what octane are you running? 22PSI seems quite high for 93 octane. I would remove the MHD backend flash, or get a custom MHD tune and remove the JB4. At the least to try to eliminate any funkyness going on with having both.

[WilsoN55]

Any updates on this? I'm curious!