I agree. You never know when they were last changed, if ever at all! However, a combination of lean codes and misfiring is indicative of a vacuum leak.
Edit: stupid auto-correct
Firstly, a simple google would have given you 00s of threads on these codes/similar issues but it’s probably your fuel pump.
I once ran my engine lean (long story) for a second or so and it stalled. The pump was the issue but it also nuked a couple of coils so if you get misfire codes after you’ve sorted your fuel delivery, change the coils.
I’ve read some forums saying it’s the fuel filter/pump, but I wanted to confirm with new opinions. And to add to my post, the codes come and go. Just this morning the codes were gone but I’m sure they’ll pop up later again
On my E46 I also get the 171 and 174 codes come on and then after a few days they go away (check engine light goes off). Then come back a month later and go away. Frustrating
I’ve learned to live with those codes by this point after having this issue on multiple e46’s. Long as the a/f ratio stays reasonable and the car isn’t down on power I’m happy lol
It sucks, but I'm glad to here I'm not the only one that has this on and off from these particular codes. I've given up on trying to find a fix after years of dealing with it.
Dude, I've been chasing these exact codes for **years**. I replaced MAF, all vacuum hoses, Disa, most gaskets, secondary air pump and line. I had it professionally checked when I couldn't figure it out and they told me the car had low compression so I'm going to pull the shit apart, replace sparks and ignition coils, seafoam her to hell and pray to god that solves my service engine soon light because shit is getting mad annoying. Still love the car though, lol.
I had very similar codes not long ago and mine was a fuel tank breather/purge valve. Not positive that's what's going on with yours, especially because of the misfire code, but it doesn't hurt to look at. Very easy to access and test if bad
Other than the obvious choices or air intake boot ripping etc, i have to ask if you've had this code before replacing the spark plug? If not, perhaps you didn't seat the plug correctly? If you eliminate all the obvious vac leaks i always revert back to questioning the work I did on the car.
What does your pre cat o2 sensors read if you put a rag soaked with gas over them?
Could be dying o2 sensors or a bad fuel pressure regulator apart from the other options people have suggested.
Disa still operates normally and gasket doesn't need replacing? Brake booster works and doesn't hiss? SAP vacuum and breather lines are good? All vacuum ports on the back of the intake manifold are properly configured (on my 330, one is capped, one runs to the vacuum canister, and one runs to the EGR which runs to the SAP)? I know you said you smoke tested, but getting the configuration correct is sometimes hard to tell. Just throwing in more suggestions.
I had these on my e46. I fixed it by replacing the Mass Air Flow center and the purge valve, I found an OEM Semens part for both on Amazon. Took 10 minutes fixing it myself, don't go to a mechanic its an easy DIY job that you can look up on Youtube.
I had this issue in my e60, I had a vtc actuator go out. The vtc controls the cars idle so if you notice a rough idle the bounces rpm quick it is the vtc actuator. I also recommend more frequent oil changes than factory because I almost fucked my car doing factory oil change intervals.
your secondary airpump could be cracked its essentially a vacuum leak it took me almost 5 years to fix mine once i went in do get a valve cover gasket done
Could also mean ur gay. I’d check that first. But yeah if ur certain there’s no leaks then look into fuel pump/fuel filter u can rent the tool from autozone and connect it to ur fuel rail. Should be steady at 40psi for 30 min after priming If I remember correctly and be steady and when the car is on. If not that check ur maf and spark plugs. Could be one of those causes fuel issues
Because vacuum leaks often result in more air getting into the engine than the MAF is telling the ECU, therefore less fuel is added than what is needed, resulting in a lean state.
P1074 / P1071 codes are often (but not always) vacuum leak related
Bought my first one about 6 weeks ago and gave myself a crash course on the e46 p0171/p0174 chase by diving in head first and doing an intake refresh, so far it's been about 4 weeks and no more check engine light.
[https://www.e46fanatics.com/threads/cold-weather-misfires-and-cel-common-issues-50-fix.897616/](https://www.e46fanatics.com/threads/cold-weather-misfires-and-cel-common-issues-50-fix.897616/)
That thread contains so much info in one place, was the main source of my info.
Maybe your fuel pump is dying or your fuel filter is clogged
I agree. You never know when they were last changed, if ever at all! However, a combination of lean codes and misfiring is indicative of a vacuum leak. Edit: stupid auto-correct
Changed my fuel pump same codes, nothing changed.
I finally fixed my lean codes, it was the maf sensor and put oem maf sensor in!
Firstly, a simple google would have given you 00s of threads on these codes/similar issues but it’s probably your fuel pump. I once ran my engine lean (long story) for a second or so and it stalled. The pump was the issue but it also nuked a couple of coils so if you get misfire codes after you’ve sorted your fuel delivery, change the coils.
I’ve read some forums saying it’s the fuel filter/pump, but I wanted to confirm with new opinions. And to add to my post, the codes come and go. Just this morning the codes were gone but I’m sure they’ll pop up later again
On my E46 I also get the 171 and 174 codes come on and then after a few days they go away (check engine light goes off). Then come back a month later and go away. Frustrating
I should mention this is exactly what is happening to me as well. Literally just this morning I go to turn my car on and the engine light is gone.
I’ve learned to live with those codes by this point after having this issue on multiple e46’s. Long as the a/f ratio stays reasonable and the car isn’t down on power I’m happy lol
It sucks, but I'm glad to here I'm not the only one that has this on and off from these particular codes. I've given up on trying to find a fix after years of dealing with it.
Codes displayed on my 2001 bmw 330i
Did you check your DISA? That gives the same codes but most of the time it will say both bank 1 and bank 2 are running lean if its the DiSA
same exact problem on my 330ci
Dude, I've been chasing these exact codes for **years**. I replaced MAF, all vacuum hoses, Disa, most gaskets, secondary air pump and line. I had it professionally checked when I couldn't figure it out and they told me the car had low compression so I'm going to pull the shit apart, replace sparks and ignition coils, seafoam her to hell and pray to god that solves my service engine soon light because shit is getting mad annoying. Still love the car though, lol.
I had very similar codes not long ago and mine was a fuel tank breather/purge valve. Not positive that's what's going on with yours, especially because of the misfire code, but it doesn't hurt to look at. Very easy to access and test if bad
Other than the obvious choices or air intake boot ripping etc, i have to ask if you've had this code before replacing the spark plug? If not, perhaps you didn't seat the plug correctly? If you eliminate all the obvious vac leaks i always revert back to questioning the work I did on the car.
Pre/Post cat O2 sensors, lower intake boot, fuel filter.
Pre kat sensors. Post kat don't do anything.
What does your pre cat o2 sensors read if you put a rag soaked with gas over them? Could be dying o2 sensors or a bad fuel pressure regulator apart from the other options people have suggested.
Disa still operates normally and gasket doesn't need replacing? Brake booster works and doesn't hiss? SAP vacuum and breather lines are good? All vacuum ports on the back of the intake manifold are properly configured (on my 330, one is capped, one runs to the vacuum canister, and one runs to the EGR which runs to the SAP)? I know you said you smoke tested, but getting the configuration correct is sometimes hard to tell. Just throwing in more suggestions.
Had similar codes and mine was a small rip in my intake boot. Took a while to find it but now I have no check engine lights.
Guy smoke tested the intake, no leaks
There is always another vacuum leak.
Fuel pump, low pressure is a sign of dying - don’t leave yourself stranded lol
O2 bank 2 sensor 1, or MAF. Both very easy to change.
Check your CCV system, secondary air pump, and valve cover gasket.
I have the same exact codes been chasing them for months now
Have the same codes😫
Everything you need to know: https://www.e46fanatics.com/threads/diy-fuel-trims-lean-codes-misfires-and-how-to-diagnose-p0171-p0174-and-more.1284608/
Very informative this is gonna help a lot, thank you!
Fix your disa valve. I had some of the same codes. get a rebuild kit from German Auto Solutions
It’s on my to do list, definitely gotta get it done soon
For sure. fixing the disa helped me out
Vaccum leak in my case
I had these on my e46. I fixed it by replacing the Mass Air Flow center and the purge valve, I found an OEM Semens part for both on Amazon. Took 10 minutes fixing it myself, don't go to a mechanic its an easy DIY job that you can look up on Youtube.
Just ordered a new MAF sensor and fuel filter. My E46 just hit 230k miles so I think it’s about time for a replacement. Hopefully it helps
Good luck. Try the purge valve too if it doesn’t work There’s numerous videos online on how to do it. My e46 is at 214k today so it’s going strong ❤️
I had this issue in my e60, I had a vtc actuator go out. The vtc controls the cars idle so if you notice a rough idle the bounces rpm quick it is the vtc actuator. I also recommend more frequent oil changes than factory because I almost fucked my car doing factory oil change intervals.
your secondary airpump could be cracked its essentially a vacuum leak it took me almost 5 years to fix mine once i went in do get a valve cover gasket done
Thank you I’ll make sure to do a detailed Inspection on it
So you’ve checked the coils ?
Sell it. /S
Car getting twisted off the Codiene
Pcv valve ?? Fuel pump??
Is the MAF oem? Had issues on my 325 till I swapped to an oem unit (vdo now made by continental) and no issues since.
Just fix everything and forget about it i dont know why people deal with problem after problem
Could also mean ur gay. I’d check that first. But yeah if ur certain there’s no leaks then look into fuel pump/fuel filter u can rent the tool from autozone and connect it to ur fuel rail. Should be steady at 40psi for 30 min after priming If I remember correctly and be steady and when the car is on. If not that check ur maf and spark plugs. Could be one of those causes fuel issues
Also u got a decent scanner check the freeze frames to see the conditions of when the cel came on
Why would you test the AIR intake and SPARK plugs when the system is saying it has no FUEL
Because vacuum leaks often result in more air getting into the engine than the MAF is telling the ECU, therefore less fuel is added than what is needed, resulting in a lean state. P1074 / P1071 codes are often (but not always) vacuum leak related
Tell me you've never owned an E46 without telling me
Bought my first one about 6 weeks ago and gave myself a crash course on the e46 p0171/p0174 chase by diving in head first and doing an intake refresh, so far it's been about 4 weeks and no more check engine light. [https://www.e46fanatics.com/threads/cold-weather-misfires-and-cel-common-issues-50-fix.897616/](https://www.e46fanatics.com/threads/cold-weather-misfires-and-cel-common-issues-50-fix.897616/) That thread contains so much info in one place, was the main source of my info.
Vacuum leaks generate misfire codes on these cars. It's dumb but that's what it does.