[Arexander]

Hello everyone,

My car:
2008 335i
N54 motor
33,xxx miles

Mods:
K&N air filter
Cyba scoops

Long story short, I had a Cobb AP v2 on my car since January of this year. In February, I started blending e85 (30%) + 91 octane (70%).
Around that time, I put my car on the Cobb's Agressive Stage 1 map, and car started to drive horribly. I took it to dealer, and one of the coils had gone out.

Recently, I had set it again to Aggressive mode thinking that the coils were all good. And about 4 weeks ago, it was driving fine. Until I gunned it, and a CEL code went off. I drove it on the freeway for about 20min. Parked the car, light went away, but to not take chances, I un-installed the Cobb.
I sold the Cobb AP to another member 2 weeks ago. The car was running fine and no error light.

And about a week ago, I went to the gas station, put in the 30% e85. However, there was such a long line for the 91 octane pump, that I told myself I would just fill up after work. When I left work the light came on--"Service Engine soon."
I put in the rest of the 91 octane, but the light didn't go away.
Then, I took a friend's advice by unplugging the battery for 15min., but the light still didn't go away.
Then, I waited until the gas was a little past the reserve on Empty. I refueled with 91 octane on a full tank, and the light is STILL there.

So, I took it to a local oil shop, and the p0171 & p0174 codes came up.

I have been doing research and it seems that the majority of the issues boil down to 2 possibilities:

1. Vacuum leak
--I did have an ER cp a while ago, but went back to stock.

2. Coils/Plugs
--Could it be that I should change them all, even though my car's mileage is really low?

Any advice from you guys would greatly help. Thanks so much.

[PINeely]

Those are lean codes. If you don't have catless downpipes then it is most likely a vacuum leak.

[Arexander]

Originally Posted by PINeely

Those are lean codes. If you don't have catless downpipes then it is most likely a vacuum leak.

Dizzaamm, this must be a topic usually covered. Almost 200 views, and only 1 member responded...

@ PINeely, I did change out my stock cp and replaced it with an ER cp. I went back and put it to stock about 3-4 weeks ago.

I looked 2 days ago for a leak or tear on the rubber boot for the cp, but didn't find anything.
Additionally, I listened carefully to any "hissing" sound, but heard nothing.

One thing I have noticed is that my motor has a shaky rough start in the mornings for about 5-10 seconds, then disappears. I read somewhere that this is due to a bad coil/spark plug misfire. And before I sold my Cobb AP, I did misfire, code went off, but went back to normal when I uninstalled it. A coil/spark plug could've remained slightly damaged since then.

So, yesterday, I ordered a full set of coils & spark plugs from ECStuning.
Hopefully this works out. If not, I'll see if I can get a jb4 g5 soon and hopefully erase that code.

[PINeely]

My mistake, when I first read your post I misread it as you had already changed the coils and plugs. Yes, those are probably going to be your problem. These engines really burn through plugs especially when they are tuned. People with tuned cars usually change their plugs every 30-35k. They were probably getting bad and the Cobb on aggressive went ahead and finished the job.

If that doesn't work then you are back to boost or vacuum leak. You said that you suspected the CP. FWIW I had problems with a boost leak in that area twice but didn't get codes or lights either time, just a loss in power. The first time it was a poor seal on my ER charge pipe and the second time it was the plastic duct going from the intercooler to the charge pipe, which had split.

[Arexander]

Originally Posted by PINeely

My mistake, when I first read your post I misread it as you had already changed the coils and plugs. Yes, those are probably going to be your problem. These engines really burn through plugs especially when they are tuned. People with tuned cars usually change their plugs every 30-35k. They were probably getting bad and the Cobb on aggressive went ahead and finished the job.

If that doesn't work then you are back to boost or vacuum leak. You said that you suspected the CP. FWIW I had problems with a boost leak in that area twice but didn't get codes or lights either time, just a loss in power. The first time it was a poor seal on my ER charge pipe and the second time it was the plastic duct going from the intercooler to the charge pipe, which had split.

Yea, I only had 1 coil changed. Lesson learned, dealers will always rip you off. If I would've known then that I could buy a whole set of coils & spark plugs for the same price the dealer charged me for just one, I would've gone that route and changed them all.
It's my 1st BMW, and I was under the assumption that the motors were built immaculately. I didn't know that they cheaped out on the vital parts of the motor...

I'll definitely give it another look this weekend. It's in the 90's out here in CA. So, working on the motor outside is not the business. Lol.

Thanks for your advices Pin

[PINeely]

Well, the motors themselves are nearly indestructible but the stuff attached to them isn't. That's kind of the story with BMW, in particular their cooling systems and little plastic/ rubber parts under the hood dry-rotting after some time. It really pays to DIY on these especially with pretty much every part you could need available on Amazon, and the aftermarket replacements are CHEAP!

Glad I could help. I hope you get your codes sorted out soon

[grussauto]

Did you ever find out what set the codes?

[Arexander]

Hey guys, sorry for the late response. Ever since all this happened to me with the car, i had other issues in my personal life that withheld me from getting back to the things that make me happy! lol

Anyways, what was going on at the time was that my water pump was on the verge of going out. I was traveling to see my ex who lived 2 hours away every weekend. Plus, the extra distances going to other cities while I was there.
Finally, the water pump had given up. And in addition, so did the oil sensor. Had to spend around $1300 to get it fixed--parts & labor--from a BMW master mechanic that does side work. He fixed it, and the car was all good.

Literally, 2 weeks after that fix, the fuel pump had gone out. Thankfully, I still had the fuel pump covered under the manufacturer's warranty. The only thing needed to fix on the car is to replace the oil sensor and get new oil in that bad boy.

Fortunately, the motor has been behaving, and no other problems have occurred since.
*knock on wood*

[teamraw]

Just got this code on my 335is today. So it's Likely to be a vacuum leak or coils/spark plugs ? Need help

[Arexander]

Originally Posted by teamraw

Just got this code on my 335is today. So it's Likely to be a vacuum leak or coils/spark plugs ? Need help

Have you done any mods to your engine?

If so, make sure all the vacuums are connected.

If you feel the car taking a while to gain speed or boost, then most likely it's one (or more) of your coils about to go out.

If you feel the latter, then definitely get a new set of replacement coils. I purchased mine from BMW and got a discount from the service manager. Show BMW 2-3 print-outs of other companies that sell genuine BMW coils at a decent price.
They can give you up to 30% (this depends on the dealership/service dept).

Check out mod bargains or other reputable sites that sell genuine BMW coils.

[teamraw]

My car is cobb stage 2+ at the moment last week when I was out driving the car hard I kept hearing a loud supercharge like noise above 4k rpms ?

[Arexander]

Originally Posted by teamraw

My car is cobb stage 2+ at the moment last week when I was out driving the car hard I kept hearing a loud supercharge like noise above 4k rpms ?

So you only have the Cobb modification on your car?

What map are you on?
What gas are you running and or blending?

If you're hearing a supercharge type of sound, it seems like you've modified the intake... If so, check again all your work to make sure everything is bolted right and all vacuum hoses are connected.

[teamraw]

Originally Posted by Arexniba

So you only have the Cobb modification on your car?

What map are you on?
What gas are you running and or blending?

If you're hearing a supercharge type of sound, it seems like you've modified the intake... If so, check again all your work to make sure everything is bolted right and all vacuum hoses are connected.

i am running on 91 octane and running cobbs stage2+ map my car has a VRSF FMIC, VRSF charge pipe, VRSF downpipes stock intake box and stock diverter valves.

[Arexander]

Originally Posted by teamraw

i am running on 91 octane and running cobbs stage2+ map my car has a VRSF FMIC, VRSF charge pipe, VRSF downpipes stock intake box and stock diverter valves.

Hmm I can only give you 2 advices:

1. Lower the map to see if there's any change in what you're experiencing.

2. If nothing changes from maps, replace your coils.

I replaced all of mine. Did it myself. And it cost me less than $300. Best thing I've done to the motor with no regrets.

[mmelton]

Hello,
Just recently purchased my first 07 328i about 3 months ago has about 80k on it. Went to 3 different places to check on a burning smell and was told it was my valve cover gasket so figured it replace that but 2 days later engine like came on and popped P0171 and 0174 Advance said it was coils and a BMW shop said it was an o2 sensor inside my Valve cover and id have to replace the whole valve cover about $850...any suggestions or advice would be greatly appreciate

Been a long time Honda guy but love the BWM community now! Thanks for the detailed write ups

*Edited - K just called BMW shop up to confirm diagnostic and they said it was the Crank Case Vent Valve. WTH is that!

[Arexander]

Originally Posted by mmelton

Hello,
Just recently purchased my first 07 328i about 3 months ago has about 80k on it. Went to 3 different places to check on a burning smell and was told it was my valve cover gasket so figured it replace that but 2 days later engine like came on and popped P0171 and 0174 Advance said it was coils and a BMW shop said it was an o2 sensor inside my Valve cover and id have to replace the whole valve cover about $850...any suggestions or advice would be greatly appreciate

Been a long time Honda guy but love the BWM community now! Thanks for the detailed write ups

*Edited - K just called BMW shop up to confirm diagnostic and they said it was the Crank Case Vent Valve. WTH is that!

Hi, thanks for the compliment.

As to your issues, I'm sorry, but I am not a BMW mechanic. However, maybe I can point you in the right way.

Whoever told you it was the coils and/or valve cover gasket was more than likely full of sh!t. I did a quick search on the two error codes and they both lead to o2 sensor faults.

p0171:
http://www.obd-codes.com/p0171

p0174:
http://www.obd-codes.com/p0174

Those two links offer solutions of what you can do, on your own, to try and remedy the situation(s).
Have you or the previous owner(s) modified the motor at all?

I ask because I had my downpipes replaced and they always throw off o2 sensor codes. This is because my downpipes do not have a resonator anymore. However, my jb4 unit can be used to erase this code whenever it comes up.

Since your motor is not turbo, I'm guessing that if there was any performance modifications done, then the previous owner(s) may have taken off any resonators on the exhaust pipes.
Is your car pretty loud?

If none of these, then it may be faulty o2 senors. Shouldn't cost much to replace them.