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      01-29-2012, 05:50 PM   #1
m1bjr
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Misfiring - BMW technical advice?

Hi,
I just fixed a misfire with a new coilpack.

The misfire has been subtle and coming/going for some weeks but not logging any codes and was minor.

Tonight it spluttered and went right to 5cylinders within a few seconds. it did this yesterday too when hot under light load.

The code logged was 29CF for a misfire on 3 (two days running), sure enough there was some tracking in the coilpack so fitted a new one, all sweet.
But there was also a code relating to ignition off - 29DC

So my question for a Technical Expert or SME:

Q. Does the car detect a misfire and/or O2 issues from unburned fuel and disable that cylinders injector to protect the cat from unburned fuel?
i.e. a misfire becomes a complete channel OFF and the car then runs on 5 clyinders?

This seems to be what happed (twice) as a restart led to restored 6cly operation immediately, although a slight miss was still evident on hard acceleration until coipack replacement.

Just curious

Steve
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      01-30-2012, 12:57 PM   #2
phil200tdi
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29DC:
29DC Cylinder injection switch-off
Error will cause a warning light
Error is not currently present
Test conditions have been completed
Short circuit or signal interruption

Therefore I guess the blown coilpack could have interrupted the signal and hence shut down the injector.??
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      01-30-2012, 05:05 PM   #3
m1bjr
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Thats what I am asking Phil - is this the process the DME goes through?
So is the 29DC a direct result of a busted spark plug or coil, or something else?

Just curious really mate
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      02-12-2012, 03:12 AM   #4
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That code is 29DC is signs of a failing fuel pump! I just got the same damn thing today. Its basically Cylinder Injection Cut-off. Basically low pressure in a high pressure system. Taking my car back to the dealership. I just had my fuel pump replaced last september and i barely have 5000miles on this one!
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      02-13-2012, 07:06 PM   #5
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Could be....
No long starts and runs pretty well though.
I'll do some logs in a couple of weeks with the JB4 - that shows pressure/rpm
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      02-16-2012, 07:34 PM   #6
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Quote:
Originally Posted by m1bjr View Post
Could be....
No long starts and runs pretty well though.
I'll do some logs in a couple of weeks with the JB4 - that shows pressure/rpm
The long cranks usually follow a few weeks after the misfire codes. If i remember correctly from personal experience. Then its time for a new hpfp.
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