Very lumpy, tick over + dropped revs on starting...

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Warrior
Joined: Tue 11 May, 2010 10:02
Posts: 498

  Z3 roadster 3.0i

Very lumpy, tick over + dropped revs on starting...

Post by Warrior »

My Z3 3.0i with 46k on the clock hasn't been driven much over the past 2 months but she's turned over on the key and been left to idle for 20 minutes on a regular basis.

On starting yesterday she was very lumpy, warbling and struggling as if not all cylinders have kicked in. The rev counter jumps back and forth between 500-1000. Give her a bit of gas, the rev counter jumps up to 3000 and for a few seconds all seems well, until dropping back and struggling again.

The engine outline warning lamp is showing on the dash which suggests Oxygen sensors?

MOT booked for Wednesday but I don't think I'm going to make the half mile up the road!

UPDATE I was convinced it wasn't a hose as I thought they'd been replaced just a couple of years ago, but on closer inspection split at both ends!
LaRy
Joined: Mon 12 Nov, 2018 17:47
Posts: 158

  Z3 roadster 2.8

Re: Very lumpy, tick over + dropped revs on starting...

Post by LaRy »

I suggest that you check the idle speed valve. It can be clogged, especially as our cars are getting older. In most cases, you don't have to replace the valve, just remove it and clean it inside by using brake cleaner. If you loose the valve and shake it, it should be a clicking sound from the piston inside. If not, too much dirt. Then fill it repeatly with brake cleaner and shake!
Faulty idle speed valve will give fault codes from the oxygen sensor.
Warrior
Joined: Tue 11 May, 2010 10:02
Posts: 498

  Z3 roadster 3.0i

Re: Very lumpy, tick over + dropped revs on starting...

Post by Warrior »

Thanks LaRy,

The top hose on the air filter was split underneath the jubilee clip holding it on so I effected a temporary repair with some Duck tape but if anything it got worse so removed it completely to find the other end in tatters. How the cars been running with it in that condition I don't know?

New part being delivered today but will check the idle speed valve as well. Where do I find it!!? :oops:
LaRy
Joined: Mon 12 Nov, 2018 17:47
Posts: 158

  Z3 roadster 2.8

Re: Very lumpy, tick over + dropped revs on starting...

Post by LaRy »

Look at this video. Your engine is not looking exactly the same, the video is showing what you have to do and how the valve is looking like.
https://www.youtube.com/watch?v=i210k9a8l0g&t=199s
I did not see the person disconnect the electric connection, bit it is one.
My guess is that the magnt coil inside is getting some sort of voltage ore electric frequenzy to adjust the piston of the valve. That is the reason why it does not work if it is greasy from old oil.
LaRy
Joined: Mon 12 Nov, 2018 17:47
Posts: 158

  Z3 roadster 2.8

Re: Very lumpy, tick over + dropped revs on starting...

Post by LaRy »

Hi, I think this Youtube is better filmed and probably showing the same engine as you have, a M54.
https://www.youtube.com/watch?v=lVPV-XnmJyk
Warrior
Joined: Tue 11 May, 2010 10:02
Posts: 498

  Z3 roadster 3.0i

Re: Very lumpy, tick over + dropped revs on starting...

Post by Warrior »

Thanks LaRay, will take a look later but meanwhile the new hose has sorted out the tick over, but left the ENGINE - emission values have deteriorated - warning light on the dash.

I read from other threads that giving her a good run may clear the warning light but she's out of MOT, being sorted on Friday, and that in her current state it's an automatic fail. So technically I can't drive her to a garage to get sorted, to put a meter on her, can't take her for a run :lol: :lol: :lol:
Warrior
Joined: Tue 11 May, 2010 10:02
Posts: 498

  Z3 roadster 3.0i

Re: Very lumpy, tick over + dropped revs on starting...

Post by Warrior »

UPDATE: Bought a cheap code reader, which showed issues with lean fuel mixture, cleared the fault and sailed through the MOT yesterday.

In addition something that I'd not taken much notice of, the off centre position of the temperature gauge needle, is now resolved and points due north when engine warmed up.
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