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General E46 Forum
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Old 06-08-2017, 11:22 PM   #21
Archbid
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I'd replace the MAF. I pushed it off for a few years, and the logs didn't show anything too severe. At 150k I replaced it and immediately had better fuel trims. It is not that expensive, and at some point spending hours guessing has a cost (plus it is the easiest repair ever!).

I would also cast a suspicious eye on your brake booster. JFOJ is there a way to just plug the booster hose to isolate it and see if it is the issue?
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Old 06-09-2017, 05:06 AM   #22
jfoj
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Quote:
Originally Posted by Archbid View Post
I would also cast a suspicious eye on your brake booster. JFOJ is there a way to just plug the booster hose to isolate it and see if it is the issue?
Brake booster should be ruled out, however, due to the high Fuel Trims at cruise and the fact they do not get higher at idle, I am not thinking a vacuum leak problem here.

The problem with the brake booster is the vacuum supply hose is a hard, molded hose and it is not easy or wise to pinch off. Often you will need to remove the brake booster input check valve and then plug the check valve opening with tape or have a helper put their thumb over the valve opening and see if the Fuel Trims drop at all.
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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 06-15-2017, 09:57 AM   #23
JDA33
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Alright so I've got a log from post fuel pump install. While it did make a difference, a noticeable difference, there's still something missing. Based on what you guys said and have discussed, the MAF is probably going to need to be replaced.

Link to CSV File:

https://www.dropbox.com/s/lmog5abq4c...12148.csv?dl=0

Link to Diagnostic Report:

https://www.dropbox.com/s/br0dpz0igx...6-15.html?dl=0

Side note: Pretty sure the fuel pump I took out of the car was stock. Had the hose clamp that had to be cut off and the sealing stuff still on the cap. The thing was no longer pretty white like the new one, it was pretty much entirely brown. If so I'm pretty lucky the thing somehow didn't die on me since the car was at 192k miles.
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Old 06-15-2017, 07:45 PM   #24
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Yea, unfortunately this was not the silver bullet.

A common, reoccurring theme is with these cars that are 14-15+ years old and 150-250k+ miles is they are in need of a lot of refreshing, restoring and maintenance. What happens is a lot of things deteriorate and degrade over time and performance suffers. While everyone wants and expects a single part replacement to put the car back to "new" performance levels, this is rarely going to be the case.

As you mentioned, it appears the fuel pump was in fact original and based on your comments the replacement fuel pump did make a noticeable difference, but it does not appear to have corrected the overall concern of higher Fuel Trims and lower than expected MAF readings at idle.

In the big scheme of things fuel pump, them MAF replacement is not a bad approach because if the MAF was not needed, a quality replacement MAF is usually twice as much as the fuel pump. But the fact the fuel pump was replaced, you should not need to worry about this being a problem for many years and you have not only increased the vehicles reliability, you also probably have restored some of the lost performance and we have sometimes seen a small improvement in fuel economy.

The problem with any of these degraded sensors and parts, often they are only degraded by 15% or less and there is rarely a glaring problem. Often it takes close analysis to narrow down and rule out what appears to be working to then find out what may not be working properly.

There is still a large contingent of people that believe only in the replace once broken school, which for some is the only way the world works, but when you start dealing with cars that are over 8 years old, things start to degrade and if you expect reliable transportation for a low entrance cost, you must maintain the vehicle to try to keep up the reliability.

Back to your current issue, I would say the MAF appears to be under reporting. Most of these engines typically have MAF readings of around 3.4-4.2 g/s at idle. Off idle it is really hard to determine what is a normal value, but usually if the MAF under reports at idle, it under reports at cruise.

I have found good MAF pricing at www.oembimmerparts.com, but you can search and see if there is any better pricing.
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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 06-15-2017, 09:03 PM   #25
05SMG
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My LTFT's were nearly identical to yours and improved only slightly after my new fuel pump. I had the same situation of low g/s numbers at idle and high LT's at cruise. I ended up replacing the MAF with a Siemens VDO and that resolved my trim issues within 50 miles of driving.
Just my 2 c.
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Old 06-15-2017, 09:45 PM   #26
tks
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Had similar problems as you, replaced the Maf eventually, and problems went away.

It's not as easy as replace this and boom you're done and it's certainly not easy buying one part for $200 but when that part originally lasted 150k you get your money's worth I suppose.

I replaced everything like you and the last item, holding out for any other item to replace, I initially did not buy a Maf lol... And then it ended up being the Maf!! Cleaning didn't help either.
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Old 06-30-2017, 03:21 PM   #27
JDA33
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And then it ended up being the Maf!! Cleaning didn't help either.
Well I appreciate all the responses. There seems to be a common trend among you guys posting that had similar issues so.

I decided to pull the trigger and order a new Siemens VDO Sensor. Needed to order new brake pads anyways. I'll post up some logs after the install. Thank you again to everyone for the help

Last edited by JDA33; 06-30-2017 at 03:22 PM. Reason: Still Can't spell
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Old 06-30-2017, 04:08 PM   #28
05SMG
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Success!
Btw.....cleaning a MAF with the fancy CRC doesn't really work. Learned that from jfoj.
Enjoy those lower numbers.
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Old 06-30-2017, 05:06 PM   #29
jfoj
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Originally Posted by tks View Post
Cleaning didn't help either.
This is the problem, cleaning a MAF is generally a waste of time. The way to determine if cleaning the MAF is going to help things is to get a baseline MAF reading in g/s at idle.

Remove and clean the MAF, reinstall the MAF and then check the baseline value, if there not a 10% or greater change in the MAF reading when compared to the baseline, cleaning the MAF changed NOTHING!
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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 07-17-2017, 11:45 AM   #30
JDA33
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So the lovely new VDO MAF sensor arrived about a week ago and I installed immediately. I'll get a log of the idle and upload at some point. Only log I have currently with the new MAF installed is of turnpike driving at 75+ MPH.

Took a nice trip this weekend, about 250 miles round trip, and we are looking good. Did quite a bit of highway driving which is what would generally proc the ses light/codes. No light, no codes, and the car feels great.

It is also the first time since owning this car that OBDFusion is telling me the car is ready and would pass NJ Emissions testing. I did pass when I went a while back in this thread, but that was probably from using the CRC Guaranteed to Pass fuel additive.

On a side note I'd just like to give my continual thanks to everyone who's posted and helped me out. Now that the thing is in pretty solid shape and has come a long way I might make some kind of transformation thread. I know I always enjoy reading those, and this car has come a long way.
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