Hello, I have a modded R53 that has begun misfiring under hard acceleration. First I'll give a list of my mods.

- 15% reduced supercharger pulley
- Airtec CAI
- Miltek sport headers
- Miltek sport Cat-back
- NGK spark plugs

The misfiring started happening around the time I installed my CAI. At first the car was running fine but quickly started to misfire, use a lot a gas and generally preformed worse. I figured thos would be an issue with my ignition so I replaced my leads with NGK leads and my coil pack with another OEM coil pack. This fixed a lot of the misfiring but the car still seems to not be running the best.

Could it be that my car requires a tune or is there something else I didn't think of that could be causing this.
Also sorry is I posted this in the wrong spot.

 

I'll bet the "car" isn't misfiring, I'd bet it's the engine..!

Do you have any idea what you did to the fuel mapping adding all of those free flowing parts ? You've leaned the system too far. You now need more fuel to go with the newly added air flow..!

Mike

 

You putting the OEM coil back on should give you a clue. Sometimes all those After Market bolt-on's make things worse.I would go back to the stock CAI and see what;s what. All those bolt-ons you have should not require a tune..

 

Although many things on modded Mini, can cause misfire.
Air leaks in the intake, fouled plugs, failing cam position and or crank position sensors. Dirty map sensor, worn out valve guides, causing the valves not to seat. Bad fuel to air ratio, should be 14 to 1. And quite a few other things.
First step is to get a scanner on it, to detect codes.

 

Could be as simple as worn plugs, too. Did you check them?

I had a misfiring issue that would occasionally result in a thrown code on my 06. It would always happen under heavy load (pushing hard on gas pedal). Checked the codes and found that the misfire was on cylinder 4. Pulled the plug and found that the center electrode was badly worn. Replaced all plugs and has been running smooth ever since.