Misfiring

m1bjr · 01-29-2012, 05:50 PM

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

phil200tdi · 01-30-2012, 12:57 PM

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.??

m1bjr · 01-30-2012, 05:05 PM

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

badass335 · 02-12-2012, 03:12 AM

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!

m1bjr · 02-13-2012, 07:06 PM

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

Jay2301 · 02-16-2012, 07:34 PM

Quote:

Originally Posted by m1bjr

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.

01-29-2012, 05:50 PM	#1
m1bjr LSD - No, you're not seeing things 75 Rep 3,302 Posts Drives: Baby F36 Gran Coupe Join Date: Mar 2010 Location: Plymouth UK iTrader: (4)	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 __________________
	Appreciate 0 Tweet Quote

01-30-2012, 12:57 PM	#2
phil200tdi Colonel 115 Rep 2,621 Posts Drives: 335i M Sport E90 LCI manual Join Date: Jan 2011 Location: Aylesbury iTrader: (1)	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.?? __________________ Car: e91 330d with Viezu map Gone but not forgotten: 2010 Jaguar XFR (Cat-back exhaust, pulley, intake mods and map), Highly Modified E90 335i LCI M Sport Manual (circa 480BHP/500lb ft)
	Appreciate 0 Quote

01-30-2012, 05:05 PM	#3
m1bjr LSD - No, you're not seeing things 75 Rep 3,302 Posts Drives: Baby F36 Gran Coupe Join Date: Mar 2010 Location: Plymouth UK iTrader: (4)	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 __________________
	Appreciate 0 Quote

02-12-2012, 03:12 AM	#4
badass335 Lieutenant Colonel 116 Rep 1,948 Posts Drives: 2017 540i Xdrive Join Date: Jul 2007 Location: Surrey, BC iTrader: (10)	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!
	Appreciate 0 Quote

02-13-2012, 07:06 PM	#5
m1bjr LSD - No, you're not seeing things 75 Rep 3,302 Posts Drives: Baby F36 Gran Coupe Join Date: Mar 2010 Location: Plymouth UK iTrader: (4)	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 __________________
	Appreciate 0 Quote