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Roger, BMW Master Tech
Category: BMW
Satisfied Customers: 3045
Experience:  10 yrs. experience as BMW Master Technician, shop foreman and dealer.
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Dear Sprinkles08. I have a BMW e90 lci from 2009 with the

Customer Question

Dear Sprinkles08. I have a BMW e90 lci from 2009 with the N53 engine and the apparently well know "rough idle when cold"... I've changed all coils and plugs and injector on cyl. 6 which reported a misfire. It was coded. However the misfire remains. It comes on after 10-20 secs on cold starts, cuts the fuel to cyl 6 and when warm I can delete errors and it runs smoothly... What on earth is going on with these engines? ;-)
Submitted: 10 months ago.
Category: BMW
Expert:  Steve replied 10 months ago.
Hello and welcome,

My name is ***** ***** it will be my pleasure to assist you today.
what is the exact fault you are getting?
Customer: replied 10 months ago.
Hi Steve - The fault is that the engine misfires after 10-20 secs of smooth running upon a cold start. After that the yellow engine light comes on, the car shudders and is definitely not firing on all cylinders. I have both Bmw INPA and Rheingolds ISTA/D to help me, but I'm confused on this one. It appears that after the engine lights has been turned on the ECU detects a misfire on cyl 6 and stores a fault code 29D2 / P0306. When the motor heats up after 5 mins I can turn it off and on again and the fault is gone. The engine runs smoothly and has no issues when warm. So I changed all plugs, all coils and injector on cyl 6. I noticed the version of the injectors on bank 1 were all suffix 11 while the injectors on bank 2 were suffix 7. This tells me that the former owner must have changed the ones in bank 1. Now that cyl 6 is suffix 11 I would suspect that this would cure the problem, but it didn't... I've been working on bmw cars for the last 6 years and I feel I know my way around diagnostics, but this puzzles me. I can see from the internet that this particular engine has had issues with injectors. Some will state that you can only change 6 at a time, some say one bank, some say it's okay to change just one injector. I have no problem with spending money on spare parts, but wouldn't want to just change parts until problem disappears. Oh, btw, I have changed the low pressure sensor just before the high pressure pump, to be on the safe side... I look forward to hearing from you:-) Best regards Thomas