Mixture too lean, P0171, P0174, P0313

[Lushbunny]

I just purchased a 2001 BMW 330CI as well blue/tan leather. Picked it up from a used car dealership. First BMW I've ever had, and I'm really excited to actually do some work on it. SEL went on after about 500 miles of driving. I had Autozone read the codes and it came up with:

P0313 - Misfire detected with low fuel
P0174 - system lean bank 2
P0171 - system lean bank 1

I noticed that my MPG is really low at about 16mpg city driving, but not hard driving. I also notice a whistling noise when I accelerate from idle. Once it gets going the noise disappears.

I changed the air filter, had an oil change.

What should I check first? Intake boots. Vacuum Leaks. or spark plugs? Any advice would be helpful.

[mcoxpdx]

Check intake boots first. Those likely are the vacuum leak. Go from there. Tons of threads with pics of that problem. Read up.

[ezbmr]

I just had mine fixed, new oil separator, new intake boots, problem solved, just like new

[fixiturself]

best to use a small open end wrench and then turn them over when replacing the boot and use a small socket with a flex extension. THE DEALER MUST PUT THESE ON FROM UNDER A LIFT.

[fixiturself]

Okay I had the boot tear at the Y boot about 3 months ago and repaired it. Now I'm getting all the codes p0171 p0174 p0313 with the SES coming on within 25 miles. I took the MAF off and noticed the plastic grill end or output to engine only had 1 piece of plastic holding it on (luckily none of the plastic pieces when anywhere. I tried cleaning the MAF but the SES light came back on...seemed to last a little longer though. Tried spraying carb cleaner but no noticable leaks. Question will the MAF work without the plastic grill properly? And could a bad MAF give these codes?

[fixiturself]

yes you can cut away the boot, but you can probably get it off and have room by just disconnecting the upper boot with the MAF on it

[fixiturself]

My lower boot connection where it connects to the intake manifold was sliding off from the bottom. I guess the best way to make sure it's connected good is look inside the boot and make sure it snuggs up to the manifold. Then make sure the clamp stays in the rubber track on the boot while tightening it up. (that's where I had my problem from the previous install, sliding off track on the bottom).
All turbo sounding howl is gone.

[Arustik1]

While putting everything back together I had a hard time getting the partition back in and in the process the black hose came off.

The hose made a sizzling sound which sounded like a lot of lost pressure. Now the car starts, but just chokes after 2-3 seconds.

Here is a picture.

Any thoughts?

-D

[nathancarter]

That hose goes to your brake booster, and I strongly suggest that you DO NOT DRIVE the car until it's properly reconnected. Without that hose, you won't have power brakes (though you can still stomp the pedal REALLY HARD to brake).

The OEM hose clamp isn't really re-usable, not without special tools anyway, so you may need to pick up a generic hose clamp (looks like 3/4" or 1") to replace it.


...also, I never had to remove that partition to get to any of the relevant intake parts.

[HimyKabibble]

HELP! My '01 325i has been throwing all the sames codes as the OP listed for the last month. Resetting the light, it will stay out for anywhere from a few hours, to a few days, then come back on. Today I removed the intake boots, and both are just fine, despite their age, and 150K miles. I also looked at the MAF, and it is clean as a whistle.

So, what else should I check? There are no unusual noises, so no obvious indication of a vacuum leak. I need to get the thing smogged, but can't do that with the light on....

Regards,
Ray L.

[danewilson77]

Could have an intake leak around DISA. Remove and inspect. Upon reinstall a light coat of Permatex on rubber gasket may help.

How is the car generally running?

[HimyKabibble]

Thanks. The car is running fine - no problems at all.

What is the DISA?

BTW - All the hoses on the engine appear fine, EXCEPT for the little (roughly 1/8") vacuum hoses, which are all literally turning to dust. I've replaced a few of them, but suspect there are more. I suspect this may be my problem. Is there any diagram anywhere showing where they all are?

Also, seems like when the SES comes on it always complains about BankA first, though BankB has come up later on as well. Is there anything that is specific to BankA that could be the problem?

Regards,
Ray L.

[Deltasquare1]

Hi

I own a 528 1998 and i always have this OBD2 code 0160, the plugs and intake boots, are new. Does anyone as i idea of this problem^
Thanks

[auaq]

New to this forum, so hello!

Same symptoms here as has been generally described by everyone with same dtc's. I can hear the whistling noise while driving. Rough idling on cold start but soon enough smooths out as it gets warmed up.

Definitely indicates a vacuum leak usually on the intake boot. Checked it and found a hairline crack on the end of the intake boot which fits on to the idle control valve. Have already put a rtv silicone gasket, but doesn't make a difference on the rough idling and also doesn't make a sense to me because a minute hairline crack is just not enough to trigger these problems. It is likely to be but something tells me it is not enough to make my conclusion. Anyways let's move on. I sprayed throttle body/carburetor cleaner on top of the following components: MAF, intake boot, brake booster plug hose, throttle body + idle control valve, intake manifold gasket and finally DISA valve. No significant difference at all for the rough idling. Just a very slight improvement when sprayed on MAF sensor and a bit on brake booster plug hose. Still no clue what is going on.

I then decided to pull everything out to inspect thoroughly as there may be some hidden clue to it. Somehow and accidentally caught a glance at one of the pcv hoses that fits between the pcv valveand the oil dipstick tube and found it to be cracked about 3/4th around it. It was cracked at the pcv valve end. In fact all of the pcv hoses were brittle so much as if it could break like a pack of chips does. This pretty much tells everything. I think what is happening is that when I sprayed on the MAF sensor and just across the boot some of the spray was going to that hose and affected the idling. You can see through it by removing the DISA valve and idle control valve.

I strongly believe that this is where the whistling noise emits from and what causes the rough idling on cold start and all the intermitting dtc's.

Now, of course, I cannot disregard the MAF sensor as one of the other culprit but I would like to consider it as the last resort. I do not think the O2 sensors are also causing all these hassle.

All of this does not mean it is/has to be the ultimate cause of the problem. It may be only applicable on my car and perhaps yours as well. So, all in all, do a thorough basic tests for these symptoms. Mind you I am writing this after I was determined to find the vacuum leak this morning and alas I finally found this. I haven't replaced it yet and soon enough will be making an online order for the complete set of the pcv system.

I highly recommend to replace the entire pcv system with the cold climate package. Do not replace just one part of it. If one is so brittle/cracked/restricted/clogged up so are the others.

As soon I replace them I will let you know my result. Till then, take care.

[nathancarter]

Thanks for the info. Leaking PCV hoses could definitely be causing that problem. Keep us updated.

I need to replace mine. I'm on the original parts at 150k miles, and have been burning an unacceptable amount of oil over the past year or so, I'm hoping it's just the PCV not doing its job properly any more,

[drmoreau]

i am STILL fighting this after nearly a year. exact same problems. intake boots are new, vanos is new, DISA is new, CCV system and all hoses are new, ICV was cleaned and inspected.....yet STILL I occassionally throw a p0174, p0171 or p0313.

it does seem to happen only when I'm low on gas though....and since I know my fuel filter is new I'm starting to suspect the fuel pump. I'm at 103k on the clock.

[PrettyRicky]

Maxis, this is just my 2 cents and it may have already been addressed in some earlier posts but I constantly got those exact same codes until I bought a Peake reader...turns out it was the crank shaft sensor 3C1D when I use a BMW specific reader....

[PrettyRicky]

Maxis, this is just my 2 cents and it may have already been addressed in some earlier posts but I constantly got those exact same codes until I bought a Peake reader...turns out it was the crank shaft sensor 3C1D when I use a BMW specific reader....

[drmoreau]

car is in the shop now, they're fixing the leaking oil filter housing and vanos return line as well as some vacuum leaks from misc lines under the intake manifold they found.

i've had it with having my head stuck under that hood, time to pay somebody else to do it. luckily we have a local shop that specializes in european cars, expensive, but still a lot cheaper than the BMW dealership

w00t! she's fixed. repair shop just called and said that they changed a few vacuum lines under the manifold and found that a seal near the VANOS was the wrong size (not sure what they meant, but I used what was provided when I changed the VANOS) and now no more vacuum leaks.

so word to the wise, if you're going to have to do your CCV system anyway take the time and do it the easier-but-longer way, remove the intake manifold.

hopefully no more p0174 codes for me.

[auaq]

car is in the shop now, they're fixing the leaking oil filter housing and vanos return line as well as some vacuum leaks from misc lines under the intake manifold they found.

i've had it with having my head stuck under that hood, time to pay somebody else to do it. luckily we have a local shop that specializes in european cars, expensive, but still a lot cheaper than the BMW dealership

w00t! she's fixed. repair shop just called and said that they changed a few vacuum lines under the manifold and found that a seal near the VANOS was the wrong size (not sure what they meant, but I used what was provided when I changed the VANOS) and now no more vacuum leaks.

so word to the wise, if you're going to have to do your CCV system anyway take the time and do it the easier-but-longer way, remove the intake manifold.

hopefully no more p0174 codes for me.

Good to know the changes and hopefully should be fine now. Any ways let us know the outcome.

[drmoreau]

Still idles a tad rough, but I still need the dme update. Still makes the whistling sound at around 5k rpms though.

[PrettyRicky]

well, this is going to sounds strange, but considering the code you got before.....it could very well mean that your fuel pump is going out.... Happened to me...total nightmare of three week period and never threw any other code besides lean mixture banks 1 and 2.....but sure enough....three weeks later and in the middle of the tollway....it goes out...

[auaq]

An update

Today at college I started working on my car at 11 am and worked up to after 4 pm. Replaced the entire PCV hoses and the oil separator. I also have replaced the intake manifold gasket and as well as the throttle body gasket as a preventive measure.

The car started right up on a slightly cold start. Could not feel the rough idling yet, however, I will try it tomorrow morning. Hopefully I should not get the rough idling on a cold start. Temperatures are now dropping to about 40+ F at night which I think is an ideal condition to experiment. Oh yes, I also replaced my spark plugs from Bosch to NGK #3199. The car has got 123k+ miles. I will drive for about 100 miles and do an oil change again as a preventive measure and wipe the oil pan as clean as possible in order to observe any leakage henceforth.

Wish me luck for tomorrow's morning cold start!

Shall let you know soon of my result.

[auaq]

Another update from me:

So far so good. The check engine light went away yesterday morning. I do not feel the rough idling any more. No whistling noise. The car is running a lot smoother than before. Haven't noticed any difference in power but just a little. I suppose the spark plugs would account for it and of course the entire pcv as well. Shall be keeping an eye on the check engine light just to make sure it does not come back.

Any way I seem to be thankfully satisfied. Shall keep you updated!

[ja8992k]

First photo is the location of the failure, with some other parts (Intake, throttle body) moved out of the way. The red arrow is the boot where the hole is. The yellow arrow is one of the two hose clamps that were the hardest part of the job. If you look closely, you may be able to notice that the head of the screw on the hose clamp is not visible - because it's pointing downwards! When I put it back together I reversed the hose clamps so the screw is pointing up.

Second photo is the big-ass hole in the intake boot.

Third photo is my ghetto repair job (yes, I've already ordered replacement parts)

Hello from Germany!

Well, i just registered to say a BIG THANKKKKKKKKKKKKKKKK YOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOUUUUUUUUUUUUU UUUUUUUUUUUUUUU!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Ive had troubles with my 330ci for sooo long!
Ive changed everything, spark plugs, oil, filters, etc...

i just saw your pictures of your intake boot.... went outside and checked mine.... and BINGO! it looks SO wasted!


THANKS A MILLION GUYS! You have saved me alot of trouble and **** days! !