It usually is a vac leak, but if not, fuel filter is decent bet. Not sure of your mileage, but fuel filters can stop a car at something like 120,000 miles if not changed--they go a while. My fuel pump was replaced at 250,000 miles...and it was fine at the time.

If you get down into the engine at all, consider cleaning your idle control valve. BTW the most popular air leak seems to be the elbow on the lower intake boot going to the ICV. If you're down there, you should probably plan on replacing it in any case.

Good luck.

...and a bump

 

Hi. Thank you. I***8217;m planing to replace the filter tomorrow. But didn***8217;t MAF flow figure of 24 at IDLE strike as totally out of wack?

 

Hi. Thank you. I'm planing to replace the filter tomorrow. But didn't MAF flow figure of 24 at IDLE strike as totally out of wack?

I would log a cold start with OBD Fusion and look at the MAF values. Read this PDF on how to configure OBD Fusion and use it to run a Diagnostic Report, log parameters, and share the logs.
https://forum.e46fanatics.com/attachment.php?attachmentid=651719&d=1489505619.
This write-up is Android specific. iOS support is similar, but the menu options may be slightly different.

Regarding the MAF:
- make sure you have a genuine Siemens/VDO MAF and not a cheap Chinese knock-off
- don***8217;t clean it, not needed and more likely to damage it
- if the log of the MAF signal intermittently goes really high, it may indicate clogged cats

Regarding the P0171/P0174 codes:
- smoke test the intake and crankcase to find the vacuum leaks
- PM replace the fuel pump and fuel filter if they***8217;re > 100k miles or questionable

 

My MAF at idle reaches 5.5 g/s max with the A/C on.

325i


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Thx. Mine too.

 

I have no advice mechanically, but I just installed a new MAF sensor...since you're in Brooklyn too, if you want, you can try it out on your car to see if that solves your problem

 

Eugene, this is an incredibly generous offer. Thank you very much! PM sent

 

The first thing to do is have the intake professionally smoke tested. You have multiple vacuum leaks. The only way to find all of the leaks is a professional smoke test. Then, clear all of the codes, reset the adaptations and start over. I bet the MAF is toast. The only MAF FYI I want to buy is one made by Siemens/VDO.

 

Thank you
I plan to take it for a smoke test. Computer diagnostic place told me that according to their findings the problem is CCV valve and associated piping. I know how to clear codes, how do I reset adaptations? Yes I know I should get VDO MAF. Are Brembi or Bosch any good?

 

Update

Update:
So fuel filter was replaced yesterday; I disconnected and cleaned MAF electrical connector; MAF is the original Siemens (no VDO on it); looked at fuel pump, it's Delphi, which is a VDO sold thru AutoZone, according to a post here on E46. So it was replaced before, probably a couple of years ago. Cleared codes. Started cold today in the morning, car gave a couple of backfires. Never happened before. After that all went well. So far no codes. But when I cleared them about twoo weeks ago, it took about a week for them to pop-up again.

Values were like this:

Coolant temp: 176 F (they were practically the same from about 125 to 180)
STFT B1 17.19
LTFT B1 1.56
STFT B2 20.31
LTFT B2 1.56
engine rpm 710
MAF 3.24 g/sec

Same temperature but at 1500 rpm both short trims went down to about 12%

At 2000 rpm they went down to 5%

At coolant temperature 194 F:
STFT B1 0.78
LTFT B1 5.47
STFT B2 -0.78
LTFT B2 6.25
rpm 706
MAF 3.66

At 1500 rpm all trims stayed within 2.34% to 3.91%

At 2000 rpm - same, but MAF was 7.00 g/sec

So do I have a vacuum leak when it's cold only? Do I have to smoke it still? BTW, car runs great, and engine /tranny feel great, I can barely feel it idling at 600 rpm in drive.

Thank you

 

Update:
So fuel filter was replaced yesterday; I disconnected and cleaned MAF electrical connector; MAF is the original Siemens (no VDO on it); looked at fuel pump, it's Delphi, which is a VDO sold thru AutoZone, according to a post here on E46. So it was replaced before, probably a couple of years ago. Cleared codes. Started cold today in the morning, car gave a couple of backfires. Never happened before. After that all went well. So far no codes. But when I cleared them about twoo weeks ago, it took about a week for them to pop-up again.

Values were like this:

Coolant temp: 176 F (they were practically the same from about 125 to 180)
STFT B1 17.19
LTFT B1 1.56
STFT B2 20.31
LTFT B2 1.56
engine rpm 710
MAF 3.24 g/sec

Same temperature but at 1500 rpm both short trims went down to about 12%

At 2000 rpm they went down to 5%

At coolant temperature 194 F:
STFT B1 0.78
LTFT B1 5.47
STFT B2 -0.78
LTFT B2 6.25
rpm 706
MAF 3.66

At 1500 rpm all trims stayed within 2.34% to 3.91%

At 2000 rpm - same, but MAF was 7.00 g/sec

So do I have a vacuum leak when it's cold only? Do I have to smoke it still? BTW, car runs great, and engine /tranny feel great, I can barely feel it idling at 600 rpm in drive.

Thank you

I just fought this issue on my 04 325i with 195K on the clock. I bought it knowing it was a trainwreck. I can say without a doubt you have a vac leak. I just found that my brand new MAF was leaking where the electronics plastic weld to the body. It was a tiny leak but I had crazy high STFT like you. The only way I was able to find it was smoke test it. You'll find some smoke.

Because of age and wear and tear, I changed everything plastic on the intake side and it's 100% tip top now.

 

If your STFTs drop at higher Rpms it usually means you have a vac leak.

You went from 17% down to 3.91%.


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Hi. Thx. What confuses me, it only happens while the car is cold, in open loop...

 

You can do your own smoke test for cheap.
https://e46fanatics.com/forum/showthread.php?t=1118879

 

Monitoring fuel trims at idle and then at higher RPMs can show you that you have a vacuum leak but a smoke test is really the only way to find it (unless you have a very obvious tear in an intake boot).

I bought a Stinger Smoke Tester and used it just yesterday to find out that my lower intake boot was not clamped on properly. Went from 12% short term trim and 10% long term trim to 5% short term and 2% long term.

Like Bali showed you can make your own and it should do the trick. If you want to spend some money and already have an air compressor then I would recommend the Stinger as its a quality piece.

What is your MAF reading at idle with no lights/radio/accessories on?

 

OBDFusion report, in PDF

OBDFusion report, in PDF

 

OBDFusion report, in PDF

My recommendation...Take the time you***8217;d spend going to any more mechanics and use it to figure out how to set up OBD Fusion for logging. With that and a smoke tester solution you***8217;ll save a ton of cash and be a happy self diagnoser!

 

3.74 g/s seems fine for an idle reading so disregard my MAF question.