Your "MAF" test is bogus. Your engine will run all day long without a MAF sensor. Just not efficiently.
Try a new air filter. Then look for leaks in vaccum lines.
Maybe have the system fogged to find a leak.

 

But again after I cleaned the MAF they disappeared, so wouldn't that tell me that if the codes came back again that it's just the MAF that should be replaced?

 

Follow this video exactly:

https://youtu.be/AsgB9eBl58I

What's the history of the fuel pump and filter?
A brand new Siemens/vdo maf cost ~$115-160 on fpceuro, but that's the last thing to change

 

Do a smoke test- you will definitely have leaks and they have to be dealt with. Remember to look behind the engine cover for the check valve hose.

Once you have replaced rotten rubber, just replace the MAF. It really isn't that expensive

 

...you will definitely have leaks and they have to be dealt with.

I think we do a disservice to our fellow owners when we tell them what the definite problem is. Although these two codes, P0171/0174, are the most common we see in these engines, the cause widely varies. Telling someone 'you will definitely have leaks' - is just WRONG. It can be a vacuum leak but it can also be many other things. The only way to know definitely, is to do a smoke test.

I chased these two codes for a bit myself and haven't seen either in more than 1100 miles - since I replaced my DISA that failed a vacuum check. Checking your DISA for vacuum won't cost anything and it takes just a few minutes.

 

The MAF is always the LAST thing to look at for lean codes, yet for some reason it's always the first thing some people think of. There is so much info here on finding intake leaks, just do some reading.

 

I suspect that is correct, but seriously at the age of these cars, just replace the damn thing if it is original and then you have eliminated it as a factor. They do wear out.

But I still think it is nuts to do such precise diagnostics if you have original MAF and hoses. All you have to do is squeeze any of the vacuum hoses and feel how brittle they are, and to replace them one by one doesn't make sense.

Replace all the vacuum hoses, replace the MAF, replace the O2 sensors (presuming they are original), clean the ICV, check the brake booster. There isn't a good reason not to provided you can afford the $150 for the MAF. They are all wear items, and if the codes remain you have dramatically reduced the complexity of the diagnostics.

 

Forget the "MAF Test" and cleaning the MAF. The MAF's on these engines do not get hydrocarbon fouled by the CCV/PCV/Crankcase vapors. Cleaning the MAF on these engine is a waste of time, cleaner and money. If the MAF is under reporting, you are not going to clean it, you will need to replaced it. DO NOT replace the MAF with a $50-$75 MAF, you need a genuine Siemens/VDO MAF from a reliable supplier, but not the dealer.

If you have Lean codes, post the Freeze Frame data so it can be reviewed.

Vacuum leaks are VERY common on these engines as they age and few of these engines do not have vacuum or crankcase air leaks at this point in their life. As for the DISA leaking vacuum, it is possible will cause Lean codes, but the leaking diaphram by itself should not cause a Lean condition because the hole is very small. If the DISA flap is freely spinning on the shaft is can cause strange behavior.

I would rule out all the basic problems with vacuum leaks first before worrying about the MAF, BUT a cheap Asian counterfeit MAF may be currently installed and this could be the source of some of the Lean conditions.

Suggest you read this thread: Solve your misfires, lean codes, rough idle - http://forum.e46fanatics.com/showthread.php?t=897616

 

Hi

I am having similar codes, instead of spinning another thread positing here.. hope that is quite okay



prior to touch MAF I have changed

1) VCG gasket
2) spark plugs
3) CCV
4) cleaned MAF twice or thrice
5) no smoke test done, but have did oil cap one I do not have any suction assuming (I know this is not appropriate) there is no vacuum leaks
6) Vacuum line for F connector to fuel filter has been replaced.
7) this does not belongs to this diag, but i have replace PS reservoir, hoses come and go from/to it along with pump

After all replaced above I went and bought this Delphi MAF but that did not helped..

my current issues are
1) p0171 and p0174

2) low millage 14.5 miles/gal local 17 gal on highway (prettY Bad)
3) small vibe/jerks right after start up
4) MAF , old N new one' showing 2.8 Grams/Sec reading at idle, I do not understand this..

any direction highly helpful.. running out of plates this month.. if you know good place around PLANO TX who does smoke test let me know.

 

Hi



I am having similar codes, instead of spinning another thread positing here.. hope that is quite okay







prior to touch MAF I have changed



1) VCG gasket

2) spark plugs

3) CCV

4) cleaned MAF twice or thrice

5) no smoke test done, but have did oil cap one I do not have any suction assuming (I know this is not appropriate) there is no vacuum leaks

6) Vacuum line for F connector to fuel filter has been replaced.

7) this does not belongs to this diag, but i have replace PS reservoir, hoses come and go from/to it along with pump



After all replaced above I went and bought this Delphi MAF but that did not helped..



my current issues are

1) p0171 and p0174



2) low millage 14.5 miles/gal local 17 gal on highway (prettY Bad)

3) small vibe/jerks right after start up

4) MAF , old N new one' showing 2.8 Grams/Sec reading at idle, I do not understand this..



any direction highly helpful.. running out of plates this month.. if you know good place around PLANO TX who does smoke test let me know.

Imho you still have a vacuum leak. Low MPG and your codes point to it.

Are you able to clear the codes with a scan tool?

 

Its Delphi MAF, yes I need to take to some local shops.. and they are charging 90 bucks for the same, I should be getting 1 on eBay for that amount ...

https://www.amazon.com/gp/product/B00V8R7F3O/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1

 

On the forums, the general consensus goes that aftermarket sensors on an E46 are a no no. You should only get a Siemens/vdo maf. It's currently $180 at fcpeuro

For smoke testing: forum.e46fanatics.com/showpost.php?p=18233704&postcount=4

 

I agree with trying the simple / cheap things first. First time I had these codes I was part swapping for 4 months with no luck - even built a smoke test tool. Decided to take it to a reputable independent and he told me to run 2 full tanks of shell 91 and if they don’t clear come back. That’s how I learned these cars do not like ethanol additives. Second time it was a vacuum leak easily found by visually inspecting the common problem areas... One part and I was done.


Sent from my iPhone using E46Fanatics

 

I've got the same two codes. Damn. Not sure if I should start my own thread, or, add to this one. I think for now I'll add to this one. Please let me know if it is better to start a new one.

I have a 2002 330cic. I've owned about 6 years. It is a summer only fun car. Has about 85k miles on it. I suspect it was a well maintained summer fun car most of its life. I only have records for parts of its life. After taking it out of storage this spring (started and ran fine) I took it on a drive. All was fine till I hit the highway and got service engine soon light. Read codes p0171 and p0174 - lean codes. I reset them, and all was fine for several weeks. Car runs and drives fine, no loss of power or misfire that I could detect by seat of pants. Then yesterday I was on the highway again, and the light came back on. I'll attach screen shots from OBD Fusion phone app.

I reset codes again, and they have not come back. I suspect they might if I take a highway drive.

I opened the hood for a visual inspection. I thought maybe a mouse or something had set up house. No obvious damage or signs of rodent (I've had that problem before - mouse/chipmunk nest under hood).
Knowing the next obvious step is to do a smoke test I thought maybe using one of the F-connector hoses might be a good place to introduce smoke, so, tried to pull it off. I could not get that thing out of the intake tube. I assume I just have to try harder. Just pull twist pull, right? Then I realized that would not be a good place, since smoke would just come out air filter intake. Intake boot looked good, no cracks, still flexible. Maybe somebody has already replaced it. Even so, before I remove it I I will have spares on hand. That lower boot looks like a real pain in the ass to get out. Will require removing DISA, which means at minimum I will also have to find a source for disa O-ring.

I'm working my way through this post
http://forum.e46fanatics.com/showthread.php?t=897616
I'm not sure how much of it is relevant since I'm not having cold weather problems or misfires. I guess the first obvious step is to just try and smoke test it. This weekend I'll try to cobble together a smoke tester. I have rubber gloves, a tube, and a cigarette. Maybe an obvious hole will be revealed.

I guess I need to also figure out how to log things using OBD fusion. I think I have instructions someplace. Are there particular logs that are most useful?

My thinking with this car if I touch something plastic or rubber I should probably plan to replace it

I have to have the car inspected in a few months. It will not pass with CEL light on, or readyness monitors set. I'm also a little concerned about running a car with lean codes . . .

 

If I recall jfoj's statement correctly, lean codes during cruising are either a degraded maf or degraded fuel pump

 

Maybe I should just search out a source of non-ethanol fuel and give that a shot ? I do add techron once a year.

 

dknightd,

Best to start your own thread on your specific issues.

BTW, FORGET about non-Ethanol fuel and/or Techron, mechanic in a can is not going to solve this problem.

I have to make some assumptions here.

You mentioned this is a Summer only fun car. So I assume the car sits for long periods. So I would run most of the current tank of fuel out of the tank, refill and see what the LTFT do while cruising. If no major improvement with fresh fuel and the Fuel Trims do not drop significantly, then there is still a problem. Lean codes at highway speeds are either due to an under reporting MAF and/or a soft failing fuel pump. I also have to assume the fuel filter has been changed, however, it is really considered a "Lifetime" filter and it is a huge filter, but I would recommend the filter be changed at 75k miles.

Do not bother trying to "clean" the MAF, it will not help. The MAF's on these engines is not subject to crankcase gasses like some MAF's and they do not get contaminated with anything that can actually be cleaned off.

If deciding to replace the MAF, Siemens/VDO ONLY, NO Bremi, No Bosch, No other names. You need to purchase from a reliable source like: FCPEuro, ECSTuning or OEMBimmerParts as there are PLENTY of counterfeits on the market and there is nothing more frustrating that spending money on a replacement part that you assume and think works, but at the end of the day perpetuates the problem and you spend more time and money trying to solve the same problem and finally find out a counterfeit part is the cause of your headaches.

 

I should probably replace my fuel pump as PM at 85K miles. But I don't notice a problem when accelerating hard, which I assume is when the fuel pump is working the hardest. Fuel filter was replaced at about 40K miles according the records I have. Apparently it is part of BMW maintenance II every 60k miles. If I'm going to replace the fuel pump. I might as well replace the filter. If I'm going to replace intake tubes, and so have to remove disa, I should probably replace it (or at least have a spare oring handy) I might as well replace oil seperator and tubes at the same time since I'd have decent access. Time and money . . . Not fun
I think I run though a tank of fresh fuel (though I did use stabil in the fall when I parked it) and go from there.
Maybe I'll take the risk of running fuel level below 1/4 tank! Just have to make sure I have some spare fuel handy when I do it.
Maybe a smoke test will revel an obvious leak - that would be nice.

jfoj is there a OBD Fusion log that would help diagnose failing MAP?

 

The fuel filter is NOT part of Inspection II as I recall, there is no suggested replacement interval from all of the documentation I reviewed.

If the filter was replaced at 40k miles, it is probably fine for now. Soft fuel pumps do not show up under hard acceleration believe it or not. Not a bad idea to PM it, $115 from FCPEuro for a Siemens/VDO pump/sending unit assembly on your doorstep last I checked.

But the MAF is likely under reporting. There is no easy/foolproof way to condemn an under reporting MAF when it is only under reporting by 5-10%. You decide based on Fuel Trim values other than the idle reading of the MAF, but often under reporting MAF's appear fine or close to fine at idle but then are problems when cruising.

The problem line is the car is OLD, it needs all the plastic and rubber under the hood replaced. It has nothing to do with mileage, it is more an age issue. Rubber lasts 8-10 years before it deteriorates quickly. While your car may or may not have multiple problems, Lean codes at cruise are going to be due to an under reporting MAF and/or a soft failing fuel pump with the MAF actually being the more common cause from experience, but often I suggest replacing the cheapest part first if you plan on replacing both.

Vacuum leaks impact cruise Fuel Trims very little, they can, but they are mostly irrelevant compared to the MAF and fuel pump.

 

jfoj thanks for you insight

 

Be careful, the leaks may not be from the valve cover gasket, but may be from cracks in the valve cover!

When the valve cover is replaced the 15 grommets must be replaces as well as these are what puts the "clamp load" on the valve cover gasket.

http://forum.e46fanatics.com/showthread.php?t=1021219

http://forum.e46fanatics.com/showthread.php?t=1053359&page=2&highlight=

http://forum.e46fanatics.com/showthread.php?t=1053359

http://forum.e46fanatics.com/showthread.php?t=1224156

 

What he said is true, but you should also be looking for vacuum (intake) leaks where there is air entering the intake at a location that is after the MAF. The MAF measures air entering the intake and reports the results to the computer, which then uses this information to set the fuel delivery schedule -- fuel injector timing. Assuming the MAF and fuel pump are working properly -- jfoj's suggestion is that they are not, which can be completely true -- then if there is air entering the intake that has not been through the MAF, then the result will be a lean condition. All I am suggesting is that you need to be sure you have no breaches in the intake that allow air to enter that has not been measured by the MAF. The list of usual suspects includes the bellows that makes the bend between the MAF and the throttle body. This bellows is whatever the diameter of the MAF is, so about 3 inches. Remove it and inspect the folds for cracks, replace if you find any. You can also do a smoke test where you connect a smoke machine to the throttle body, open the throttle plate and see if smoke comes out of any of the hoses connected to the intake.

The only reason I point this out is because the MAF and the pump are costly items, but the duct work that carries air to the engine, and the hoses that go out to provide vacuum to various valves is cheap, and prone to failure. Cheap and easy before expensive.

 

Folks a quick question

my apologies on my previous post, I said 02 sensors are leaking, but I learn those are Fuel Injectors. and will they leak, good part is fuel is not leaking....

if VCG and CCG are leaking (for instance) when we try to open a oil cap, it will be hard to open, is not it?

in my case that is not happening.. I can simple open when engine is running no resistance or suction...

 

On my car, I could open oil fill cap pretty easily with engine running. There was a slight drop in idle speed for a few seconds (which I assume is the ICV adjusting to huge vacuum leak). I have not smoked tested yet, so am not sure if I have other leaks or not.

 

OK I think I have logging figured out. I took it for a drive to test logging, and to see if I could get readiness monitors set. I got all monitors set except CAT. I think I'm allowed one test to be not ready for testing in NY

Here is the log file
https://www.dropbox.com/s/xkt6k5ayairrhe8/CSVLog_20180525_210702.csv?dl=0

Some notes:
0 sec, cold start then idle in driveway
182 sec, back out of driveway and start driving to highway
346 sec, highway onramp (I can accelerate gently on this one)
498 sec, exit highway onto cloverleaf
590 sec, had to accelerate to reenter highway in other direction
739 sec, highway ends
845 sec, warm idle in driveway

One thing I noticed LTFT was more or less constant throughout drive. About 11%.
Some things seem to change only every 4 seconds (is that normal? could it have been because I was also monitoring in real time?)
At idle, turning on/off lights or AC changed MAF reading. The variation in MAF reading during warm idle was mostly due to me turning AC and lights on and off.
It looks like with no load MAF is reading about 2.8 g/s. With lights and AC on about 3.5 g/s
From what I've read these values are probably a little low, pointing to a under reporting MAF, or a pretty big vacuum leak.

Today I hope to rig up a smoke tester, unless DW has other plans for me.
Thanks for your help

 

Looks like I have a tear in the lower intake boot.

I think I'll order upper and lower boot (genuine BMW?) MAF and fuel pump (both Seimens/VDO ?) and just do it all.

It looks like that lower boot might be a pain. Can it be done without removing DISA? If not perhaps I should also get disa repair kits since I'll have it out anyway, and it probably at least will want to have a new gasket when reinstalling.

edit: maybe I should do PCV system while I'm in there. It is a summer only car, so valve itself is probably OK, but I'm guessing at least the lower hose is getting old (the upper hose you can see actually feels fine). I suppose I might as well do it all at the same time. I plan to keep the car for several more years . . . Thoughts?

edit2: this does not look like it will be fun. I just have to remind myself I only have to do it once Unless I keep the car for 10 more years.

 

I replaced my lower intake boot without removing my DISA. It was difficult but it can be done. I had a variety of tools to help remove the hose clamps including small stuby flat blade screwdriver, long flat screwdriver and a 6 or 7mm socket (I forget which) that fits on the hose clamp.

 

I just went through the whole ordeal with P0141/P0144 on our 325 sport wagon. Keep in mind that a lean condition can be caused either by too much air or not enough fuel. We've owned this car for about two years and since the day we got it, it would occasionally throw either one or both of these codes. And even if it hadn't turned on the MIL, it generally would have these codes in the pending register. It started stumbling or bogging once in a while so I dived into it and found and fixed a couple of vacuum leaks and replaced the MAF sensor as a precaution. I checked the fuel pressure and it was fine. The problems persisted.

A couple of days ago it just completely packed it in - it was difficult to start and made no power whatsoever. So I went back to basics, attached my fuel pressure gauge and got a reading of zero. The fuel pump had packed it in. I replaced it, and the car has been flawless ever since. It has no codes, either latched or pending. This is a first.

I sectioned the old fuel pump and found that the commutator had a groove several millimeters deep cut by the brushes, and the brushes were worn down to almost nothing. After having played cat-and-mouse with this problem for well over a year, this gave me confidence that I've definitely found and fixed the problem. The car has about 160,000 miles on it.

YMMV, obviously, but keep my experience in mind.

 

Fuel pump problems are nothing new, see this thread and the pictures of worn out pumps: Fuel pump failures - http://forum.e46fanatics.com/showthread.php?t=929501

Anyone smart will just PM the fuel pump at year 8-10 if they do not want to deal with substandard performance and walking. Sure some of the pumps last longer, but it is just tick, tick, tick, tick before it starts to fail and then leaves you stranded.

It is really worth $115 to worry about it?? Towing cost most people way more than $115 plus the disruption and other hassles.

 

Especially because unlike many other repairs, IT IS SO EASY!
Only easier high-impact repair I can think of is MAF replacement.

 

Occasionally on a cold start I experience what I can describe as a stunted ignition (p1701 & p1704 present). If I clear the codes it starts fine until they come back after a short drive on the highway. Could this be symptoms of a failing MAF? Only other symptoms with codes present would be a small surge in power upon acceleration.

Additional notes: previous owner had k&n intake system installed. There is a K&N sticker with a number imprinted on the ECM in the drybox. I have replaced the upper intake boot, air box, and air filter with oem parts. I inspected the lower intake boot no cracks. I’ve attached some pictures. Anything here throwing red flags?
Thanks!

Sent from my iPhone using E46Fanatics

 

FWIW I replaced upper and lower intake boot (lower was torn). Put in a disa repair kit with new o-ring, and new MAF. My problems seems to be gone. Long term trims about 1-2% (not sure if they will continue to adjust). MAF now reads 3.5 -4.5 depending if AC is on. All ready monitors set (including CAT). Fuel pump will be my next PM, it is sitting in the box, might as well do it after I burn off a little gas. I think I let the CCV sit in the box for awhile - it looks like a pain to replace and my hoses appear to be all intact for now.
It could be just replacing the lower boot would have fixed it. It was a pretty good sized leak.