Z3 strange fuel mix(?) issue

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Inferno
Joined: Sun 30 Sep, 2012 07:35
Posts: 274

  Z3 roadster 1.8
Location: Athens

Z3 strange fuel mix(?) issue

Post by Inferno »

Hey all,
i have a problem for quite some time now, almost every time i will take the car for a ride, after like 20-30mins of driving (when it gets hot) AND ONLY after i push high revs, i can feel that the car loses power, it starts smell the rotten egg thing, and right then if i stop on the sideway, and lift my foot from the throttle car "dies", in other words it doesn't hold idle. I have to start it again, stay on the throttle for like 1 min and at that point i get black smoke from the exhaust, gunfire sounds and hickups, and after a minute staying on the throttle, it clears up, fixes itself and rides perfectly fine again.

I haverecently changed the catalytic converter specifically to solve this issue, but obviously that wasn't the problem.

In my experience it's like it gets more fuel than it should when i ask it to run fast...
Any ideas? What should i look next? Injection system? MAF?
Engine is M43, and it gives no fault codes in the diagnostic

Mike Fishwick
Joined: Fri 19 Jun, 2009 10:27
Posts: 2063

  Z3 roadster 2.8
Location: Daglan, France

Re: Z3 strange fuel mix(?) issue

Post by Mike Fishwick »

Try unplugging the MAF and see what happens.
A Z3 is not just for Christmas - it's for life!

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Inferno
Joined: Sun 30 Sep, 2012 07:35
Posts: 274

  Z3 roadster 1.8
Location: Athens

Re: Z3 strange fuel mix(?) issue

Post by Inferno »

Mike Fishwick wrote:
Mon 05 Apr, 2021 10:04
Try unplugging the MAF and see what happens.
thanks, exactly what my mechanic said just now on the phone. could be the MAF

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colb
Joined: Sat 05 May, 2012 22:46
Posts: 684

  Z3 roadster 1.8 TU
Location: Newport South Wales UK

Re: Z3 strange fuel mix(?) issue

Post by colb »

Good suggestion from Mike to disconnect the power lead on the Maf, doing so will make the car run on default settings, if it runs better like that then Maf will be the problem. Maf's don't always set fault codes them selves however when they do go wrong they affect other sensors which in turn will point you in the wrong direction as to the real cause of the problem. If you have live data diagnostics thake a look at the fuel trims, if the Maf is not measuring the air passing through it correctly a mismatch will be picked up in the exhaust by the lambda sensors, if it sees a lean condition the ecu will add more fuel at the injectors to richen the fuel mixture up, it may well set a code and light the eml after it reaches a stage where its adding 20% more fuel and gives up trying to correct what it sees as a lean mixture. Air leaks in the engines vaccum system will also cause the same effects on the fuel trims. Make sure the rubber hoses across the engine are not split or holed. These engines require a sealed vaccum system to run correctly.
Colb
1999 BMW 1.8 Z3
2003 BMW 2.5 Z4
1998 Honda Deauville NT650V

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Inferno
Joined: Sun 30 Sep, 2012 07:35
Posts: 274

  Z3 roadster 1.8
Location: Athens

Re: Z3 strange fuel mix(?) issue

Post by Inferno »

Hi again,
I replaced the MAF, (or Luft, never understood the difference) tested it for like 200-300km and it seems to be solved now!
For the record, the only fault code the diagnostic got was "Lamda sensor needs adjustment" or something like that.

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