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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Powertrain and Drivetrain Discussions > NA Engine (non-turbo) / Drivetrain / Exhaust Modifications > N51: running lean, idle dip @ start, 29E1



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      08-29-2016, 05:22 PM   #1
mushroom
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Unhappy N51: running lean, idle dip @ start, 29E1

Hello, I have '08 328i coupe with N51 engine. 82k miles on car.

It all started 3k miles ago. One day car just wouldn't start.
Fix was easy: got used fuel pump control module from eBay - $20.

But after that car started idling rough after cold start. It would start at 1200 RPM, lower it and then it would drop to 500, almost choke, bring RPM back up and continue rough idle for some time. Then it will smooth out. My gas mile

Also I've got SES light, code is 29E1. I checked adaptation values and they were (when car is warmed up):
Multiplicative mixture adaptation - 52.14%
Multiplicative mixture adaptation 2 - 71.59%
So looks like I'm running lean. Please help.
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      08-29-2016, 06:12 PM   #2
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You still have warranty on your car. Go to the dealership and let them figure it out. I wish you kept your old module in place, so they can't say that is it.

N51 in california has crazy warranty due to it's zero emission status. I think it's like 15 years and 150k on any fuel and emission equipment.
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      08-29-2016, 07:33 PM   #3
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Originally Posted by W37V View Post
You still have warranty on your car. Go to the dealership and let them figure it out. I wish you kept your old module in place, so they can't say that is it.

N51 in california has crazy warranty due to it's zero emission status. I think it's like 15 years and 150k on any fuel and emission equipment.
Well, it would be too easy. Unfortunately my car holds salvage title and apparently it voids the warranty
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      08-30-2016, 10:10 AM   #4
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If you're running lean you either have too much air and/or too little fuel. Maybe none of the above and your pre-cat O2 sensors wet the bed.

Too much air:
- Bad or dirty MAF. Clean, test & replace if necessary.
- Smoke test for vacuum leak. Repair vacuum leak if found.
- Bad (pre-cat) O2 sensors. test and replace if necessary

Too little fuel:
- Try injector cleaner.
- not sure how to test injectors, but maybe someone else can chime in. replace if necessary
- same as above with fuel pump.

Let us know what you find out.
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      08-30-2016, 10:40 AM   #5
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Quote:
Originally Posted by mushroom
Hello, I have '08 328i coupe with N51 engine. 82k miles on car.

It all started 3k miles ago. One day car just wouldn't start.
Fix was easy: got used fuel pump control module from eBay - $20.

But after that car started idling rough after cold start. It would start at 1200 RPM, lower it and then it would drop to 500, almost choke, bring RPM back up and continue rough idle for some time. Then it will smooth out. My gas mile

Also I've got SES light, code is 29E1. I checked adaptation values and they were (when car is warmed up):
Multiplicative mixture adaptation - 52.14%
Multiplicative mixture adaptation 2 - 71.59%
So looks like I'm running lean. Please help.
What state are you in? I used to have an N51 Sulev. I found out that the car is under warranty for 150k or 15 yrs. or something outrageous like that. You will have to fight with the stealership but bmwna has your back. research it print it and bring it to them highlighting pgs. 34-69 I believe.
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      08-30-2016, 11:53 AM   #6
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If you take it in have them check all the crank case ventilation lines and oil separator lines (vapor and oil return) for cracks. These lines become very brittle at this age and can crack (it happened on my car). I had something similar when trying to troubleshoot lean/rich error codes, I check EVERYTHING Simon said (lol) and found nothing. Ripped out my intake manifold and found the issue right away. If anything is wrong with that system it can throw off the entire fuel management system. It sounds like your computer tried it's best to adapt and when it ran out of adjustment it started reporting codes.

Good luck.
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      08-31-2016, 02:37 PM   #7
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Question fuel delivery?

Guys, correct me if I'm wrong, but if it was vacuum leak or MAF issue all banks would run lean.
While fuel adaptation values are different in my case. Does it mean that issue is in fuel delivery? Like low flow on one of the injectors?
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