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General E46 Forum
This is the place to get answers, opinions and everything you need related to your E46 (sedan, coupe, convertible and wagon) BMW!

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Old 08-27-2015, 07:41 PM   #1
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Join Date: Aug 2015
Location: Tx
Posts: 4
My Ride: 330ci
P0171, P0171 & P0174 so confused!!

Hi guys, I'm new to this forum. Saying that I have being reading this forum for months now, and I'm still confused. So here goes!

I bought my car (2004 330ci convert) first week on June. Two days later the SES came on, so I took it to Autozone the guy showed me the code and it was only P0171. He said it might be a bad tank of gas ( as I had just pumped a day ago) and had added octane booster to the tank before that one as I thought the previous owner only put regular in it. Anyways the light still stayed on after that tank and is still on.

Now when I got it read a day ago, the codes are P0171, P0171 and P0174. I'm confused because it shows P0171 twice.

The car up until yesterday has run without any issues whats so ever. Now at around 2000 rpm I can hear a noise (like a rumble) sounding like its coming from the left side of the engine bay. It doesn't sound bad and I haven't lost performance, I just don't think I've heard it before!

Also now and again my car will take a few seconds longer then usual to start up. This is always after I've driven it, and never on the first start of the day.

Under the hood the car looks brand new, I've looked at the first intake hose past the MAF and it's still in good condition like I said everything looks new!

If anyone was any idea what might be causing this please let me know!

Thanks in advance!!

Last edited by Dazzae46; 08-27-2015 at 07:49 PM.
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Old 08-27-2015, 08:26 PM   #2
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Join Date: Nov 2009
Location: Fairfax, VA USA
Posts: 23,010
My Ride: 330CiC, M5, X5, E93
Do not be confused nuub.

Your car has problems, all E46 have problems.

Do not listen to the clowns at the parts store. The counter jockeys are that for a reason.

Read away, pay attention, follow directions.

Get an OBDII smart phone/tablet App and interface, typically $30 or less. These Apps are usually best for drivability issues and they support Emission Readiness Monitor Status, Freeze Frame and Live/Realtime data. They are also great for Logging data for review after the car has been driven and can really help find unusual problems.

Android - Touch Scan for $5.00 and ELM327 OBDII to Bluetooth interface.

iProduct - OBD Fusion for $9.99 and ELM327 OBDII to Wifi interface.

Some people prefer to have an extension cable to keep the interface away from their feet.

Something like these cables are often of interested:



I usually suggest getting the OBDII interfaces from Amazon if you are located in the US/North America. Make sure you choose an interface that indicates that the order will be "Fulfilled by Amazon" otherwise you may be waiting for WEEKS for an interface to arrive from Asia. Ebay is another option, but pay attention where the interface will be shipped from, again weeks for an interface from Asia, so if you can wait and want to try to save some money, go for it, but if you need an interface soon, choose wisely.

Read the 2 links below:



Need to see Freeze Frame info if the SES/CEL/MIL is on and Fuel Trim values at both warm idle and a steady highway cruise between 45-60 MPH.

MAF issues, first cleaning a MAF RARELY resolves anything, the only thing it usually cleans is your wallet.

If you have recently replaced the MAF, put the original back on the engine until you sort out all of the obvious issues. There are MANY counterfeit MAF's on the market and the major trap is ASSUMING the MAF is not the problem since it was recently replaced. Also quite often the MAF is NOT the cause of idle related Lean conditions and misfires, faulty MAF's usually under report the airflow as a percentage and are more of a problem at highway cruise speeds and not engine idle.

Unplugging the MAF will often cause the engine idle to be smoother, reduce or eliminate idle misfires. This DOES not mean the MAF is bad, it is due to the DME going into a fixed fuel Map mode that is typically by default Richer than when the MAF is connected and this will mask Lean conditions caused by intake and/or crankcase air leaks.

P0102 means for some reason there is not likely a signal from the MAF. Verify if the MAF connector is properly plugged in, sometimes the female terminals in the connector are spread and loose on the MAF pins, sometimes there are broken wires inside the wiring harness between the MAF and the wiring box near the throttle body and sometimes the MAF just is bad with no output signal.

WARNING - DO NOT buy a cheap ebay MAF, there are many Asian counterfeits on the market that do not work properly. See of there is an MAF reading in Grams/Sec. Most E46 have an idle MAF reading of between 3.5-4

Note, there may or may not be Lean Codes showing up. Lean Codes usually trigger at around 10% Fuel Trim values or higher. Keep in mind that sometimes these engines can have a Lean condition that does not or only intermittently triggers Lean Codes. This is why monitoring the Fuel Trims in real time is important. Ideal Fuel Trim values are typically in the 0% to +2.5/+3.0% range.

Read this thread - http://forum.e46fanatics.com/showthread.php?t=1057387

Make ABSOLUTELY sure the O2 sensor wiring has not been mixed up, read these links:



Read my "BMW 20 Questions" comments in this thread - http://forum.e46fanatics.com/showthread.php?t=1059972

Check for or be aware of cracked valve covers and bad valve cover gaskets:




This information ASSUMES that spark plugs have been checked/replaced. If they have not been inspected, you also need to check for oil filled spark plug wells due to a leaking/cracked valve cover gasket.


Search YouTube for Scotty Smoke Test. Do what Scotty does or build a tester from related video. Remove the oil fill cap and make sure the crankcase fills up with smoke, put the oil fill cap back on and check for leaks around the valve cover, oil fill cap, dipstick tube and CCV hoses. Cracked valve covers are pretty common on the E46 as it ages.

Note that the Scotty Smoke Test method is not so good for smaller air/vacuum leaks or fully filling the engine crankcase, for this you really need a smoke machine that can provide a solid and continuous low pressure smoke stream. So plan on building a smoke tester of you thing you will use if more than once or may have smaller and harder to find leaks.
Solve your misfires, lean codes, rough idle - http://forum.e46fanatics.com/showthread.php?t=897616

Fuel pump failures - http://forum.e46fanatics.com/showthread.php?t=929501

Temp Info - http://forum.e46fanatics.com/showthread.php?t=964491

Hidden OBC Menu - Check Voltage, Temp, Fuel Level - http://forum.e46fanatics.com/showthread.php?t=239619

E46/E39 GM5 Door Lock Info - www.bmwgm5.com

Lower hose temp switch O-ring - BMW #13621743299
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Old 08-28-2015, 06:16 AM   #3
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Join Date: Dec 2007
Location: straight out da bronx
Posts: 6,161
My Ride: 04 330i jet black
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those are lean codes, replace your lower intake boot, clean icv and rebuild disa while you at it

clear codes, monitor for new codes after work

bought the car and 2 days later ses comes on, same old sh!t

world is full of dishonest crappy people

"if polarity comes from protons, does morality come from morons?"

Originally Posted by russ330 View Post
"Mommy and Daddy are getting a divorce now because wasp9166 had to piitb with Mom."

Last edited by wasp9166; 08-28-2015 at 06:17 AM.
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Old 08-28-2015, 08:20 AM   #4
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Join Date: Jun 2015
Location: Ohio
Posts: 251
My Ride: 2004 330ci Vert
Yea typical e46 - previous owner probably didn't work on cars himself/herself and just wanted to pawn their problem off on someone else without disclosing all the information a buyer would like to hear. Best advice is to listen to jfoj, read his posts and links carefully. Wasp is also on point with problem areas you may want to lean toward, before just buying the parts, take them apart/clean them and check the condition of them, but most likely you'll end up finding a disa in disarray, a dirty icv, and a cracked lower intake boot. It's also possible that none of those things are your problem, but most likely will be down the road.

On a cold start your car doesn't take into account your oxygen sensors until it's warmed up, which may be what your experiencing after you've driven it during the day the harder than usual starts or rougher idle after a warm start, most definitely you have a vacuum leak if not accompanied by a soft failing fuel pump or clogging fuel filter.

Not much else to say other than read jfoj's post and report back when you've found/fixed the problem or need some more guidance!

Good luck!
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Old 08-28-2015, 09:43 AM   #5
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Join Date: Aug 2015
Location: Tx
Posts: 4
My Ride: 330ci
Thanks guy I appreciate the input!! When I get some free time I'll take a better look at it, and report back!
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e46, fuel filter, fuel pump, p0171 p0174, vacuum leak

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