Arrrghh... Not firing on cylinder 3

Chazzy

Zorg Legend
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Jul 14, 2015
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83
Location
Northampton
I was happily driving into work this morning when I noticed something didn't feel right on the Z. Engine sounded rough and wasn't idling/pulling properly.

In my lunch break I went to check on it and it's not firing on cylinder 3. I fired up the engine and then individually disconnected each coil pack to identify which cylinder is the problem. I didn't have much time, but did swap the coil packs on 2 and 3 to see if the coil pack was the issue but it doesn't appear to be. When I get home I'll take the plug out to see what the condition is like, and see if it's firing at all. If not, then it could be the plug, but if it's not the plug, I'm in for a world of pain.

Has anyone else had any issues like this?
 

mrscalex

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As always best to start by reading the error codes.

You should find loads of similar issues by googling.

I was looking last night as I have a misfire after doing my engine swap.

I'll be having a go tonight.
 

Chazzy

Zorg Legend
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Jul 14, 2015
Points
83
Location
Northampton
Unfortuantely I still haven't got round to buying a fault code reader. I really should get one!
 

Lee

Zorg Expert (I)
British Zeds
M Power
#ZedShed
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Mar 26, 2014
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Basingstoke
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Z4 Coupe 3.0si
I had this once on my M, It had lost half the electrode casing it to badly miss fire. Hopefully its just the plug.
 

raymond

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Oct 15, 2016
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EAST SUSSEX
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Z3M
Same thing happened on mine. A coil pack had burned out. When a new one was fitted the mis fire was still there. I pulled the new coil pack out and fitted an old plug but there was no spark. Traced the wiring to the DME but wiring was ok. DME was faulty.
 

Chazzy

Zorg Legend
Joined
Jul 14, 2015
Points
83
Location
Northampton
Same thing happened on mine. A coil pack had burned out. When a new one was fitted the mis fire was still there. I pulled the new coil pack out and fitted an old plug but there was no spark. Traced the wiring to the DME but wiring was ok. DME was faulty.
Ouch, what did you do? Did it require a whole new ECU or was it just the relay? Was it repairable?
 

raymond

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Oct 15, 2016
Points
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EAST SUSSEX
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Z3M
First problem was actually getting the top off of the DME box. The screws are threaded twice so only just managed to get the lid up as the screws were rusted . A new DME is over £1000 plus coding and second hand ones are a bit rare for the M. A "specialist" wanted the car brought to them where it would cost £250 just to remove and test it. In the end I sent it to ECU doctor in Plymouth. £246 all in and they replaced a circuit and gave me a years guarantee. Don't run the car too far on 5 cylinders.
 

Chazzy

Zorg Legend
Joined
Jul 14, 2015
Points
83
Location
Northampton
First problem was actually getting the top off of the DME box. The screws are threaded twice so only just managed to get the lid up as the screws were rusted . A new DME is over £1000 plus coding and second hand ones are a bit rare for the M. A "specialist" wanted the car brought to them where it would cost £250 just to remove and test it. In the end I sent it to ECU doctor in Plymouth. £246 all in and they replaced a circuit and gave me a years guarantee. Don't run the car too far on 5 cylinders.
Thanks for the info - I hope it doesn't come to that. Luckily it's only 13 miles home so I'll nurse it back. If it turns out to be the ECU I might be able to get someone at work to fix it, I'd imagine it'll be a failed driver in the ECU itself, difficult to know without opening it up though!
 

Tfp

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Dec 20, 2015
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Cambs
I wouldn't risk driving it anywhere with one cylinder not firing.

A £60 recovery charge is cheaper than damaging the bore.
 

GazHyde

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Dec 2, 2011
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226
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Berkshire
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Z4 MR
I had this once on my M, It had lost half the electrode casing it to badly miss fire. Hopefully its just the plug.
Yeah, that was a mess that plug. Found your pic from the time,

 

Chazzy

Zorg Legend
Joined
Jul 14, 2015
Points
83
Location
Northampton
Last night I found the cause of the problem, it was the plug. I took out the plug from cylinder 3, although it didn't look too bad. I then swapped it with cylinder 4 and the problem moved to there. Looks like the plug had run out of life. I've ordered a new set and will fit once they arrive.
 

mrscalex

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Last night I found the cause of the problem, it was the plug. I took out the plug from cylinder 3, although it didn't look too bad. I then swapped it with cylinder 4 and the problem moved to there. Looks like the plug had run out of life. I've ordered a new set and will fit once they arrive.
Always best to check the simple stuff before letting yourself get too hot under the collar.

My misfire went away by itself. I put it down to blowing the cobwebs out of the system after it had sat idle.
 
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