Z4 2.5si running terrible

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tractorbob2.5si
Joined: Mon 11 Apr, 2016 19:58
Posts: 5

  Z4 roadster 2.5si

Z4 2.5si running terrible

Post by tractorbob2.5si » Wed 13 Apr, 2016 00:02

Hi
Just managed to get on here and hope for a bit of help.

September last year bought a Z4 2.5si auto roadster 2007 with 34k miles and been over the moon.

Noticed over the last month or so that when sitting in drive at a junction etc the engine seemed to miss slightly. This has got progressively worse to the point today where it is almost undrivable. Starts nice from cold but doesn't take long until it starts running really badly.

Been lurking on here until I finally got the account activated today and have looked at all similar threads so have checked coil packs and although I initially thought it was the issue, it runs so badly that it really is difficult to tell if there is a problem here? Disconnected the maf sensor and no difference so guess it is fine? Had the vanos solenoids out and cleaned, again no difference.

Obvious questions, any ideas what to look for next? Should be able to read fault codes tomorrow. As it was quite low mileage when we got it the service history is a bit scetchy. Guess it can't be as simple as plugs as it runs quite nicely from cold and when pushed hard does clear and pull quite well. Do the faults need to be cleared to make a difference?

Any help would be greatly appreciated as its a daily drive for the misses and although I have a good specialist garage that I use, both he and us are stuck for time so could do with getting even a relatively quick fix so it can be booked into garage at a time that fits better.

Cheers

Del
Joined: Sat 19 Nov, 2011 18:35
Posts: 2120

  Z3 roadster 1.9

Re: Z4 2.5si running terrible

Post by Del » Wed 13 Apr, 2016 10:36

Obviously only an internet guess based on your low mileage car so I’ve ruled out things like CCV/EGRs – faulty things that commonly show up worse when getting hot are 1) ignition coils as the resistance increases with heat and 2) The lambda sensors – particularly the pre-cat primary ones. These sensors do not come into play immediately upon starting from cold – as the coolant warms, the coolant temperature sensor brings in the lambda sensor(s) which work in tandem with the MAF sensor to regulate the fuel/air mixture to normal running mix. If a lambda is faulty it could give all sorts of erroneous information to the ECU and cause bad engine running. I would first get the car plugged into a diagnostic tool before ripping out expensive sensors based on guesswork. :(

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Robert T
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Joined: Mon 12 Jun, 2006 11:35
Posts: 10002

  Z3 roadster 1.9
Location: Cheshire

Re: Z4 2.5si running terrible

Post by Robert T » Wed 13 Apr, 2016 11:08

Hi and welcome to the forum.

I've seen a misfire when warm on a M44-engined Z3. This turned out to be a duff coil pack and we diagnosed with INPA (diagnostic software), which reported a misfire on one cylinder. We first tried swapping the HT leads over (not sure if you will have HT leads on the Z4 - the six-pot Z3s don't) and the problem stayed in the same place. Fortunately I have the same engine in my car and we tried my coil pack and the problem went away, so the guy went away and bought a replacement coil pack. You can use the same procedure on cars with individual coil packs by simply swapping between cylinders and using diagnostics to see if the problem moves.

It could of course be something else entirely, and looking at the fault codes should help you determine what it is. It is worth clearing the codes, running the car for a bit, then plugging it back in to see what new codes have been logged.

Cheers R.
Arctic Silver '99 Z3 1.9 & Black '59 Frogeye 1275cc
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tractorbob2.5si
Joined: Mon 11 Apr, 2016 19:58
Posts: 5

  Z4 roadster 2.5si

Re: Z4 2.5si running terrible

Post by tractorbob2.5si » Wed 13 Apr, 2016 20:49

Thanks for your replies.

Managed to get the fault reader plugged in just there and hopefully good news and hopefully just as mentioned. Misfire on 4 and 6. I couldn't really tell any difference when disconnecting the coils at the weekend , but hopefully worth getting another coil to add to the one I got at the weekend. Any other advise welcome and I will keep updating.

Del
Joined: Sat 19 Nov, 2011 18:35
Posts: 2120

  Z3 roadster 1.9

Re: Z4 2.5si running terrible

Post by Del » Wed 13 Apr, 2016 22:52

As its a low mileage car, is it possible that you still have the original spark plugs? - It's the sort of thing that certain servicing regimes might overlook if they were focusing just on the mileage. 9-year old plugs used intermittently for "shortish" journeys (typical low mileage car use profile) could break down with age. It would be unusual (but not impossible) for two coil packs to fail at the same time.

Certain items like spark plugs and air filters usually have a Main Dealer change regime which involves the first to occur of a certain mileage or 4-years - switching to an Independent garage can cause this to get overlooked. If it were my car, I would scrutinise what has been changed and when. If there was any doubt, I would change the lot.

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Robert T
Site Admin
Joined: Mon 12 Jun, 2006 11:35
Posts: 10002

  Z3 roadster 1.9
Location: Cheshire

Re: Z4 2.5si running terrible

Post by Robert T » Wed 13 Apr, 2016 23:10

Whilst a set of plugs is not going to cost the earth, the coil packs are probably a bit pricey to change all six! You could try swapping the coil pack from say cylinder 1 to one of the two showing misfires, take the car for a run and see if cylinder 1 now reports a misfire. If it does, it is the coil pack, if not, then swap them back and try swapping the spark plugs over instead. You should be able to quite quickly determine if either is the source of the misfire and you then know what to replace. If neither has any effect, then you know you are looking for something else.

Cheers R.
Arctic Silver '99 Z3 1.9 & Black '59 Frogeye 1275cc
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tractorbob2.5si
Joined: Mon 11 Apr, 2016 19:58
Posts: 5

  Z4 roadster 2.5si

Re: Z4 2.5si running terrible

Post by tractorbob2.5si » Thu 14 Apr, 2016 07:10

Yeah, I agree with all that. I have a set of plugs and air filter coming today. Hopefully get to the bottom of it tonight after work. Should be able to quite quickly now get to the bottom of the problem and also then know in my own mind what has and hasn't been done when I can get it to the local specialist to start a regular maintenance regime!

Cheers

Del
Joined: Sat 19 Nov, 2011 18:35
Posts: 2120

  Z3 roadster 1.9

Re: Z4 2.5si running terrible

Post by Del » Thu 14 Apr, 2016 09:03

Sorry when I said "change the lot" above, I meant the plugs and filters not all 6 ignition coils. :D

tractorbob2.5si
Joined: Mon 11 Apr, 2016 19:58
Posts: 5

  Z4 roadster 2.5si

Re: Z4 2.5si running terrible

Post by tractorbob2.5si » Thu 14 Apr, 2016 11:29

Del wrote:Sorry when I said "change the lot" above, I meant the plugs and filters not all 6 ignition coils. :D
Yeah- I understud that!

Cheers

tractorbob2.5si
Joined: Mon 11 Apr, 2016 19:58
Posts: 5

  Z4 roadster 2.5si

Re: Z4 2.5si running terrible

Post by tractorbob2.5si » Thu 14 Apr, 2016 19:53

Bought another coil today and fitted tonight. Purring like a kitten again! Now time to keep on top of the servicing .

Thanks for the help and replies. These forums are so useful!

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