BMW 335D and X5 35D - Diagnostic Questions

Cheap Diagnostics Before Throwing Parts at a Car

  • Have you checked for vacuum leaks with a mityvac?
  • Do you have any CEL codes?
  • What scan tool are you using?
  • Have you replaced or swapped your vacuum converters?
  • Have you tried driving with your MAF unplugged?
  • Have you tried pressure testing the boost plumbing and intercooler system?
  • Has your car had CBU cleaning done lately or inspection to see if you have CBU?
  • Have you checked the vacuum to the large turbo actuator by the firewall while idling and driving?
  • Have you checked your MAP sensor for CBU?
  • Check vacuum to the large turbo actuator while it's idling and while driving.
  • Use a mityvac to actuate the large turbo actuator, make sure it works properly.

Throwing Parts at a Car

  • Replace all vacuum lines
  • Block off EGR cooler and delete it's vacuum actuator.
  • Install a new vacuum converter by the firewall, if that doesn't improve things, swap it to the front one or replace both
  • Replace your MAF
  • Replace your MAP sensor
  • Consider CBU cleaning