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Misfire
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OnlineAveZ4coop
- Member
- Posts: 399
- Joined: Thu Nov 16, 2017 11:08 pm
- Location: Peterborough
Misfire
Worth looking at the spark plugs and coil packs first as relatively cheap to buy (always replace them all as a set). Could be damp causing an issue with these, or it could just be a coincidence? If the misfire only occurs when you put your foot down, it would point to these. If you can, borrow a code reader and see if there are any codes, will help other people on here with deeper knowledge, assist your diagnosis.
Montego blue 2006 BMW Z4 coupe 3.0si with black interior, ZHP, Whippy, 12mm front/16mm rear spacers on BBS 108's wrapped in Michelin PS4's. :driving:Brand new Pierburg water pump fitted at 101k after failure 
(should have done it at 100k) 
(should have done it at 100k) 
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raymond.harper
- Senior Member
- Posts: 1010
- Joined: Sun Aug 14, 2016 12:30 am
Misfire
A model-specific code reader is needed, a Creator+410 or my favorite an Ancel BM700 to see what is going on. Perhaps as it is wet, you are not revving the car so much as you usually do so the fault becomes more apparent.
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MEV Z4
- Newbie
- Posts: 24
- Joined: Sat Jan 13, 2024 10:26 pm
Misfire
Coil pack(s) is a good suggestion, if one of them is failing then you still might not get an engine light / code (Until the misfire gets much worse).
Coil Packs tend to deteriorate over about a week (And the misfire will get worse). A failing coil won't give issues a at random times. (Unless its not properly connected). (Make sure those little brown wires that go onto the rocker cover (next to the coils) are tight).
Yes I agree with AveZ4Coop -A coil related misfire would be particularly noticeable under acceleration / load though the car may still idle perfectly well.
Note - A single failing coil can cause the others to work harder and therefore fail shortly afterwards (Or the others fail shortly afterwards as they're all the same age). There's no issue with replacing a single coil - Before I fell out with my local garage they were doing it all the time. (They though they were too good to adjust the handbrake on my 2004 E46 Estate 330i). If you have to get x6 coils the cost adds up - and you wont be happy if it did not solve....
If you do get an engine light, the car can tell you which cylinder is misfiring with a Code Reader so you can get just one coil if you want. As the engine rotates the Crankshaft Sensor notes its speed, on each compression stroke it expects the engine to slow a bit then speed up a bit on each firing stroke, the engine turns in a 'jolting' fashion - So if the firing stroke on a particular cylinder is slower than the others then the computer can tell which one. (You may get Code Misfire on Cyl 3. where Cylinder 1 is the front one). Then swap the suspected faulty coil and see if the code moves with it.
Or you can try disconnecting each coil pack in turn with the engine running (Wont harm it) and see if you notice anything related to a particular cylinder . However you WILL get a Fault Code and you WILL then need a code reader to clear it.
Personally I'd replace the Crank Sensor as that does give Weather Related issues.
It's about £25, it's located on the side of the block near the Starter Motor and simply unbolts (One bolt) and then unplugs at the other end.
They fail as the metal coils in them swell up and the insulation inside breaks down in them or the wiring frays - The computer uses the info from it to spark / open injectors etc at the right time. (Symptoms of failed crank sensor are Long Start, Random Cut Out, Weather related issues, Random Misfire, Random No Start).
You may not get a code / warning light as the information from the Crank Sensor might not not yet be out of tolerance enough to set it off.
Note - the CrankSensor is located on the block it does not get much heat to dry it out (Linking it to damp / weather issues).
My VW Golf MkIV 2.3 used to cut out when it got near a puddle, the Cranksensor on that is located right at the front so it gets splashed / rained on a lot. Replaced it and that never happened again.
NOTE - CrankSensors seem to have a strict life expectancy of 12- 20 years after which they *****WILL***** give up. Even if this does not solve the issue it's an easy try and it's a matter of time before it will go out anyway.....
Since I fell out with my local garage last year I've been doing all this 'stuff' myself.. Since then I've found the following that backup this suggestion -
2002 Golf needed a Crankshaft Sensor (Cut Out going through puddles)
2008 1.4 Micra need Crankshaft Sensor (Had the light on / long start / random cut out)
1996 Volvo V70 2.3 Turbo - Sat there for4 years because of No Start, Random Cutout, Long Crank, Poor Idle, Misfire. Crank Sensor was rotten and I had to drill it out- Started instantly after Crank Sensor replacement.
Summary - In my humble opinion Crankshaft Sensor is the most likely cause of weather related issues.
Coil Packs tend to deteriorate over about a week (And the misfire will get worse). A failing coil won't give issues a at random times. (Unless its not properly connected). (Make sure those little brown wires that go onto the rocker cover (next to the coils) are tight).
Yes I agree with AveZ4Coop -A coil related misfire would be particularly noticeable under acceleration / load though the car may still idle perfectly well.
Note - A single failing coil can cause the others to work harder and therefore fail shortly afterwards (Or the others fail shortly afterwards as they're all the same age). There's no issue with replacing a single coil - Before I fell out with my local garage they were doing it all the time. (They though they were too good to adjust the handbrake on my 2004 E46 Estate 330i). If you have to get x6 coils the cost adds up - and you wont be happy if it did not solve....
If you do get an engine light, the car can tell you which cylinder is misfiring with a Code Reader so you can get just one coil if you want. As the engine rotates the Crankshaft Sensor notes its speed, on each compression stroke it expects the engine to slow a bit then speed up a bit on each firing stroke, the engine turns in a 'jolting' fashion - So if the firing stroke on a particular cylinder is slower than the others then the computer can tell which one. (You may get Code Misfire on Cyl 3. where Cylinder 1 is the front one). Then swap the suspected faulty coil and see if the code moves with it.
Or you can try disconnecting each coil pack in turn with the engine running (Wont harm it) and see if you notice anything related to a particular cylinder . However you WILL get a Fault Code and you WILL then need a code reader to clear it.
Personally I'd replace the Crank Sensor as that does give Weather Related issues.
It's about £25, it's located on the side of the block near the Starter Motor and simply unbolts (One bolt) and then unplugs at the other end.
They fail as the metal coils in them swell up and the insulation inside breaks down in them or the wiring frays - The computer uses the info from it to spark / open injectors etc at the right time. (Symptoms of failed crank sensor are Long Start, Random Cut Out, Weather related issues, Random Misfire, Random No Start).
You may not get a code / warning light as the information from the Crank Sensor might not not yet be out of tolerance enough to set it off.
Note - the CrankSensor is located on the block it does not get much heat to dry it out (Linking it to damp / weather issues).
My VW Golf MkIV 2.3 used to cut out when it got near a puddle, the Cranksensor on that is located right at the front so it gets splashed / rained on a lot. Replaced it and that never happened again.
NOTE - CrankSensors seem to have a strict life expectancy of 12- 20 years after which they *****WILL***** give up. Even if this does not solve the issue it's an easy try and it's a matter of time before it will go out anyway.....
Since I fell out with my local garage last year I've been doing all this 'stuff' myself.. Since then I've found the following that backup this suggestion -
2002 Golf needed a Crankshaft Sensor (Cut Out going through puddles)
2008 1.4 Micra need Crankshaft Sensor (Had the light on / long start / random cut out)
1996 Volvo V70 2.3 Turbo - Sat there for4 years because of No Start, Random Cutout, Long Crank, Poor Idle, Misfire. Crank Sensor was rotten and I had to drill it out- Started instantly after Crank Sensor replacement.
Summary - In my humble opinion Crankshaft Sensor is the most likely cause of weather related issues.
