Mixture too lean, P0171, P0174, P0313

[nathancarter]

Lower intake boot is the usual culprit, but I changed both. There's also a a plastic ring between the two boots, you probably don't need to change it. Your old one is probably fine.

The last couple of hose clamps are hard to get to. If you have the new parts in hand, you can make the job MUCH easier by cutting the old lower boot off with a razor knife. Also, a flexible screwdriver helps a ton with this job.

Consider cleaning your ICV (idle control valve) while you're in there; it's the part connected to the small hose of the lower boot. Brake cleaner or carb cleaner should do the trick.

[TEAMFALCON]

Finished replacing boot. I took some good pictures and will post up soon.

The old lower intake boot was in good shape, still replaced it. Also tightened and cleaned adjuster unit, it was pretty dirty.

The interesting thing is that I went to auto zone and had the codes run again.

Some didn't now up anymore only the:

P1083
Definition
Fuel Control mixture Lean (bank 1 sensor 1)

Explanation
Low Fuel Pressure

Probable Cause
-Large vacuum leak on engine
-Failed MAF sensor
-Ignition or fuel injector fault

P1085 (same as above, bank 2)


These are not there anymore.
P0171-system too lean(bank 1)

P0174-system too lean(bank 2)

The guy at auto zone said pretty calmly, "it's your gas cap".

Getting a new gas cap soon. He said he is not able to 'reset' the light. I guess I have to find a way to reset the SES light.

[nathancarter]

Hmm, don't think I really buy it. A faulty gas cap will give "EVAP System Small Leak" codes. Or maybe large leak, there are at least two different codes.

There are other possible locations for intake leaks, as described on the first page of this thread; cracked intake boots are the most common but not the only ones. Or, it could be lean because of low fuel supply... depending on your mileage and the quality of fuel in your area, you might change your fuel filter - it's good maintenance to do so anyway.

[TEAMFALCON]

I'll post pics up in a min of my DIY.

[autoxerwgn]

I'm not a fan of the MAF cleaning sprays. I've seen people in my shop use it and have the car come back after a couple of days or weeks with the same or different faults, but relating to the MAF still and required replacement anyway.

Since you are getting a lean code, there are a couple of common things that I've seen personally. MAF could still be a problem, bad crank case vent valve, or bad seal on the DISA valve. Without throwing parts at the car, the easiest thing to do is probably have a shop smoke test the intake to check for leaks. If none are found, try the MAF and see what happens. If you are having idle issues, my guess would be the crank vent valve or the mass air flow. Usually the DISA seal doesn't leak enough to cause misfires or poor idle, just mixture faults.

[stanggt9050]

New Guy here...
Had the SES light going on and off for a few months but it seemed to go off after fill ups so I thought gas cap. This past month or so the SES light stayed on all the time so I took it to Pepboys for a free scan and got the P0171-system too lean(bank 1) P0174-system too lean(bank 2) codes and a P0128 (Coolant Temp Below Thermostat Regulating Temp). I googled the codes and got this link. Felt my intake tube for a tear and sure enough there it was, 2 of them to be exact. Bought a new intake tube, installed and cleared codes with my new code reader. Hopefully this fixes the problem as I am pretty sure it will. BTW, the car is a 2003 330 CIC with 80k. As a side note my mileage went down 7-8 mpg in the past 6 months or so and I am hoping this fix will put my mileage back to 32-26 freeway. In addition when I bought the car (used) I noticed the whistle and asked the dealer about it and they said "its normal". Now after reading this thread I know better. Great board, thanks for the data and look foward to more posts in the future.
As for the P0128 code since I cleared the codes i will see if it comes back and address it at that time...I assume thermostat, will research some more.

[Lynk]

Hmm. Thank you, gentlemen (and any ladies). My CEL popped yesterday morning, on a very cold morning, while driving my buddy to work. I've noticed a small whistling throughout the summer, so this thread seemed a reasonable first check. My car is throwing lean codes on both banks.

Sure enough, my '05 330i has a good-sized tear. I can't tell you how thrilled I am to have a $20 fix. The local dealer has one in stock, which is now set aside.

[ricardoh]

I also have the same problem I used the OBD-II scanner on my car and it reads P0174 and well what I would like to know is what sensor is bank 2 is it the one closest to the front of the car or the one closest to the firewall?

[danewilson77]

Have you inspected for intake leaks first? This would be the least expensive fix/cause.

What is the code your car is throwing? P0174?

[ricardoh]

I inspected my intake for leaks today and didn’t find none and as of for the code that the scanner reads it is p0174-system too lean (bank 2) and I-drive reads emissions increased when I first start the vehicle. When I inspected for leaks it was just an inspection without removing the boot that’s good enough right? I don’t have any whistling but I will be double checking tonight when I can put my car in a more quite place.

[danewilson77]

Yeah...you don't need to remove anything...but ensure the inspection is thorough, and be especially mindfull of the corrugated area......below

[ricardoh]

Thanks for the help and the picture it really helps, I’ve only had my BMW for about a month I purchased it at the beginning of November and have been on this forum reading like crazy trying to learn everything about it ever since.

[danewilson77]

ok...no prob

[dustymiller]

Hello everyone, my 2000 E46 330i has engine light on, codes P0171, P0174 and P0313. When inspecting the intake boots for leaks I noticed a small pipe located under the intake boot had snapped off from its connection.
Can anyone please help me to identify this pipe, it can be seen in the following image (page 2 of thread)

http://img.photobucket.com/albums/v60/hky001/2-22.jpg

It comes from the engine just above the rear of the alternator, and connects to another pipe attached to the firewall just behind the heater valve. Looks like a nylon pipe with rubber sleeve at each end.

Also shown here, http://i237.photobucket.com/albums/f...g?t=1211401550, with CT Fuel 7 504 304 printed on sleeve.

Could this be what is causing my fault codes?
Any help would be very much appreciated.

[john209]

checked everything that everybody mentions on thread. and in my situation the whislting noise was the idler pulley. The p0174 and p0171 p0183 and p0185 were caused by my valve cover gasket. reason i know is because i checked all the vacumm stuff that people mention here but my main cause was my valve cover gasket as i replaced my old one the new did not sit right in the back part. so some how this causes vacumm leak. so i would check these two things before buying your maf sensor pulley is only 50 to 60 at local parts store idler pulley goes bad because it is self packed so if it breaks it starts whislting hope this helps please reply

there are several other hoses and things that can tear and develop leaks and cause the same codes and problems.

i replaced pretty much all vacumm hoses and it was valve cover gasket not sitting right and the idler pulley was the whistling sound

KENBBMW you should really check your idler pulley located on you alternator and for the to lean codes i would check valve cover and vacumm hoses my was new valve cover not sitting right

Hello everyone, my 2000 E46 330i has engine light on, codes P0171, P0174 and P0313. When inspecting the intake boots for leaks I noticed a small pipe located under the intake boot had snapped off from its connection.
Can anyone please help me to identify this pipe, it can be seen in the following image (page 2 of thread)

http://img.photobucket.com/albums/v60/hky001/2-22.jpg

It comes from the engine just above the rear of the alternator, and connects to another pipe attached to the firewall just behind the heater valve. Looks like a nylon pipe with rubber sleeve at each end.

Also shown here, http://i237.photobucket.com/albums/f...g?t=1211401550, with CT Fuel 7 504 304 printed on sleeve.

Could this be what is causing my fault codes?
Any help would be very much appreciated.

it is called the bottom rubber boot for your throttle body

[pj530i]

I got these exact same error codes and changed the bottom boot. Job wasn't too bad since my clamps were pointing toward the back of the car, probably because someone had done it before.

That theory was supported by what I found after removing the boot..


Someone tried to patch the cracks instead of just replacing the $25 part. Oh well, hopefully the SES light stays off.

[san141]

I have the exact same codes and problems that you had experienced when you had a tear in your Rubber Intake boot. A repair shop wants to run a smoke test for $500 but I think I should just tell them to replace the boot. How difficult is it for them to do this? I know the part is pretty inexpensive, I'm just concerned with labor. Any advice you can give would be most helpful!

Thanks for all the insight!

[danewilson77]

I could replace both boots...in way under and hour...all day long. Do eeeeeeeeeeet yourself.

Very ez.

That way you pay..maybe 30 bux...and that's if you replace both boots...

Did I say......do eeeeeeeeeeeeet?

[nathancarter]

500 bucks for a smoke test is nuts. Should be an hour labor, tops.

It's really not a job that requires any special training or fancy tools. I'd say, get the boot from an online supplier and give it a shot yourself, or find a wrench-experienced friend or family member to give you a hand. It's a little frustrating getting to those last couple of hose clamps, but if you have the new part in hand, you can cut off the old boot which makes things way easier.

[san141]

500 bucks for a smoke test is nuts. Should be an hour labor, tops.

It's really not a job that requires any special training or fancy tools. I'd say, get the boot from an online supplier and give it a shot yourself, or find a wrench-experienced friend or family member to give you a hand. It's a little frustrating getting to those last couple of hose clamps, but if you have the new part in hand, you can cut off the old boot which makes things way easier.

I'm debating about giving it a shot myself- The mechanic who reported the codes (who is obviously ripping me off) and replaced the ignition coil and spark plugs said he did not notice any tear in the rubber intake boot, but from what I read in the posts it sounds exactly like what the problem is. Thank you for all the advice!

[danewilson77]

Really? So you're debating about doing it yourself?

Mmmmm...

[DAES]

What if I am able to hear the whistle but have no tear anywhere. What could it be? Or does the whistle when accelerating definitely means air intake leak and nothing else?

[danewilson77]

What if you don't hear a whistle and you have a tear?

Do you have a tear. HAve you inspected the boots.....360 degrees with a 5X lens....?

Please look here.....



Do eeeeeeeeeeeeeeeeeeeeeeeeeeeeet!!!!

[mrdeejay]

no, there was no magic solution. I tried lots of different tools. What worked best for me was a very long flat-head screwdriver, and lots of patience. I think i turned the screwdriver with my left hand, and held the tip in place with my right hand.

I don't understand why they were put on that way. There's an indentation next to the throttle body that you can use to easily access the hose clamps, if they are installed with the screw heads facing up. Perhaps the factory installer didn't realize that the difference was significant.

well guys.... I dnt wanna say that im an eminence. But i removed the upper and lower boots in less that half hour ....

I dnt know how u guys doin it but i only use a 1/4in drive ratchet an 6mm long socket..

And guess what??? I put em back the same way..hahahaaa...

The worst of all...

The code p0174 came back after 5miles of driving in addition with p0155... Dnt know what to do now!?!?!?!?

Forgot to day my lower boot it was cracked same as nathan'z, so i did a nice temporary fix with electrical tape ... Im researchin online for a good quality cheap set of boots to replace, but im gonna remove the whole intake assembly and replace all the stinkin' vaccum hoses that i can see and clean tha "maf" & "icv"..

Hopefully this fix the problem.. I keep u guys informed...

Thanx guys...

[DAES]

What if you don't hear a whistle and you have a tear?

Do you have a tear. HAve you inspected the boots.....360 degrees with a 5X lens....?

Please look here.....

I did checked the boot and hoses and they seem in good condition. Where else can I look?