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About alexwagner

  • Rank
    Shank's Pony


  • Car Make
    BMW Z4M Roadster
  1. Z4 M Engine Light

    LAMBDA MYSTERY??? Hi guys, I have a Z4M with 26K miles. The symptoms I'm getting are much like thoses described for the lambda probe: - yellow check engine light comes on and stays on for 2 weeks, then goes off for a week, then comes back on - hesitations on partial throttle - holding back on full throttle for a couple of seconds - 4 times on the motorway (once every 2 tanks of fuel), the car suddenly developped major stuttering (+ check engine light) as if running on barely 3 cylinders. This forced me onto the hard shoulder. I cut the engine and restarted 5 secs later. All was fine again after each of the 4 incidents. --------------- Problem is, the car is showing no sensor-specfic error codes (just a general misfire code or a lean mixture code, i.e. a code for the symptom rather than the cause...) BMW has already changed all 6 coils and plugs under waranty - to no avail. They reckon it could be the fuel pump playing up, due to swallowing some gunk. My questions to you guys: 1) Do you think this is the lambda probe problem? 2) If NOT, then what on Earth else? 3) If SO, then why no lambda probe error codes? 4) Without lambda probe error codes, how does one know which of the 4 probes to change? 5) In view of the apparent frequency of the lambda probe problems on this forum, should I just consider the lambda probes to be consumables and have all 4 changed - almost as a preventative measure? 6) Or should I just have the 2 pre-cat probes changed and see if it's any better? This is getting FRUSTRATING - not so much the cost as I'm still under waranty but the hassle and the fact that I LOVE my M When if runs properly! ;-) Thanks guys! Alex