BMW Maintenance

Maintenance/Common Issues Reference Sheet

Applicable Vehicles :

WM 2007-2011 335i

WM 2007-2011 335xi

WM 2010-2013 335is

WM 2008-2011 135i

WM 2008-2010 535i

WM 2008-2010 535xi

WM 2009-2010 X6 xDrive35i

WM 2009-2014 Z4 sDrive35i

WM 2011-2014 Z4 sDrive35is

WM 2010 Z4 xDrive35is

WM 2010 X5 xDrive35i

WM 2011-2012 BMW 1M

USDM 2011 X5 xDrive35i

USDM 2011 X6 xDrive35i

Maintenance and what to expect:

It is recommended to be aggressive with all factory recommended maintenance intervals mentioned in your owners manual. This is even more important when you're asking for higher performance levels out of the vehicle. We recommend replacing spark plugs/coil packs every 30k miles in order to sustain peak performance with an aftermarket calibration. 

If the vehicle is exhibiting random or constant misfiring check the following: fuel pump and injectors (early production cars), condition of the spark plugs, and carbon buildup on backs of valves.

Carbon cleaning is needed as early as 25K miles. All cases are different in terms of severity of the buildup and this situation is increasingly detrimental to performance. Needs physical inspection to be sure of the degree of buildup which includes removal of the intake manifold.

Example of dirty carbon coated intake valves vs. just cleaned. Recommended to use the walnut blasting method but other chemical and mechanical scraping methods also work but will cost more labor. Dealerships charge upwards of $1000 for this carbon removal service so shop around.

Earlier years 2007-2008 HPFPs are common to fail as well as both turbos. BMW USA has traditionally replaced these under warranty as it's well documented with TSBs.

Charge pipes more common on N55 to blow off of the throttle body at ALL performance levels. Simple replacement with a COBB charge pipe fixes this. Be sure to purchase a new OEM O-ring from your local dealership as it is not supplied with our charge pipes.

OEM air oil separators clog and build up pressure over time causing valve covers to leak. 

Thermostats on N54 are electronic and prone to failures.

DTC P20FF Fuel Pump Plausibility code - Common but does not mean there is an issue with our OTS maps. Happens with stock BMW ROM programming. Existing BMW coding issue that has never been resolved.

These are the big reoccurring things that we notice with BMWs. Other issues can exist on a case by case basis.

Common Issues (all cars):

Incremental cylinder timing corrections that keep appearing and don't go away. Appears under "Cyl(1-6) Timing Cor" monitors. Confirm basics such as correct OTS map and octane vs parts all line up.

When you see consistent timing corrections, -3 degrees or more on 3 or more consecutive cylinders, that is something to be more concerned with. BMW's use individual cylinder timing corrections to deal with active knock.

Here is a small data sample showing a lot of timing corrections across all cylinders that are consistent. Cylinder 1 shows a quick -4 correction which is not good. The tune, fuel, and or mechanical condition of this vehicle needs to be inspected. 

Look for throttle closures on datalogs. How do I know if that is happening? Your looking for Load Requested to be equal to or less than Actual Load. If this is the other way around that will cause the ECU to close down the throttle plate and very likely will cause immediate knock events.


  • AAT – Ambient Air Temperature
  • CCT – Catalytic Converter Temperature
  • ECT – Engine Coolant Temperature 
  • EOT – Engine Oil Temperature
  • EVT – Exhaust Valve Temperature
  • MBT – Minimum Timing for Best Torque
  • AFR – Air to Fuel Ratio (Lambda)
  • DC – Duty Cycle (used with various solenoids)
  • ECU – Engine Control Unit (also known as PCM)
  • MAP – Manifold Absolute Pressure (Post-Throttle)
  • OAR – Octane Adjust Ratio
  • FRP – Fuel Rail Pressure
  • LTT – Load To Torque
  • OTS – Off The Shelf
  • OB – Overboost
  • LSPI – Low Speed Pre-Ignition
  • CAT – Charge Air Temperature
  • COT – Compressor Outlet Temperature
  • EFT – Exhaust Flange Temperature
  • TOT – Transmission Oil Temperature
  • IAT – Intake Air Temperature
  • BL – Borderline (for ignition timing tables)
  • CL/OL – Closed Loop/Open Loop (for fueling tables) 
  • DTC – Diagnostic Trouble Code
  • O2 – Oxygen Sensor 
  • TIP – Throttle Inlet Pressure (Pre-Throttle) 
  • VCT – Variable Camshaft Timing
  • VSS – Vehicle Speed Signal (MPH/KPH)
  • TTL – Torque To Load
  • FBO – Full Bolt Ons
  • UB – Underboost
  • PD – Power Demand
  • VE – Volumetric Efficiency

Copyright 2024 © COBB Tuning Products LLC. All Rights Reserved. |