Running RICH... Not me, the engine!

[fernando306]

I wish it was me, but it's engine that has been running rich.
Spark plugs are brand new, OEM bosch. New air filter as well. The car starts and runs fine for the most part, little uneven / hesitation occasionally, but not much.

Just scanned and would love to hear what you guys think, at least where to start troubleshooting.
Video of OBD Fusion reads: https://youtu.be/kiHXwIfMZes

Can you help?

Thanks a lot!

[328 Power 04]

I would verify fuel rail pressure at idle. It should be right under 51psi up to 51psi. At higher rpm, it should be right around 51psi, this is the 3.5bar that your fuel pressure regulator should be regulating.

[fernando306]

Sorry for the newbie question, I've never measure fuel pressure before, could use some tips.

Would this kit work well?
https://www.amazon.com/BETOOLL-0-140...s%2C185&sr=8-3

Quick research found this, should I expect the same?
https://www.youtube.com/watch?v=axxl98lToN8

[Muzz258]

The Other item to check is your MAF. Make sure that it still the Siemens VDO MAF your car came with and not an aftermarket knock-off.

The MAF should be measuring around 3.5 g/s at a hot idle.

[fernando306]

The Other item to check is your MAF. Make sure that it still the Siemens VDO MAF your car came with and not an aftermarket knock-off.

The MAF should be measuring around 3.5 g/s at a hot idle.

Thank you my friend. The MAF is reading exactly that!
Have you guys seen my fuel trims? It's at the first few seconds of the video.

[Muzz258]

An over reporting MAF can cause rich conditions. With the MAF telling the DME that the amount of air that is entering the engine is more than what there actually is. The pre-Cat O2 sensors see less oxygen that is expected, a rich condition. The DME then reduces the fuel to fix the readings at the O2 sensors. This gives negative fuel trim numbers.

Checking the MAF value at hot idle is an easy check and your MAF is spot on.

I have read about a test for the MAF, but have not tried it yet. That is to Monitor the MAF in g/s and to plot/chart, that's right, graph paper and pencil or using Excel to chart the results. The test is to slowly increase the rev in the engine, let them settle and take the MAF reading. Raise the engine rev's again and take another reading. Do this is say 500 rpm increments up to 3,500 rpm. When you plot the results it should show a straight line.

[fernando306]

Hey my friend,

Thanks for the fast reply, you've been very helpful. I'm going to graph is ASAP and report back.

[fernando306]

Sweeping from 1000 to 4000 RPM, this is what the MAF looks like:

1020 RPM = 1.01 lb/min or 7.63 g/s
1487 RPM = 1.53 lb/min or 11.56 g/s
2058 RPM = 1.75 lb/min or 13.23 g/s
2488 RPM = 2.38 lb/min or 18 g/s
3071 RPM = 2.82 lb/min or 21.3 g/s
3546 RPM = 3.65 lb/min or 27.6 g/s
4003 RPM = 4.06 lb/min or 30.7 g/s

What you think?

[Muzz258]

...

[fernando306]

Hey Muzz, thank you my friend for the graph. I agree, especially because under reporting would make it lean, not rich.
O2 sensors look fine too. The negative fuel trims are on both banks, so I am skeptical of a leaky injector. Fuel pressure tested just fine too. Damn, what else could it possibly be?

- - - Updated - - -

Clogged CAT maybe? Just throwing it out there...

[Clearancediver]

Idle question, but I have an ‘04...

Have you cleaned your idle control valve? This might clear up the occasional hesitation you say you are experiencing.

Not sure it has any effect on the running rich issue.... but you never know.


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[fernando306]

Muzz, today I was replacing the expansion tank in it and decided to clean the MAF. Well, as soon as I look at it, I discover it is a CHINESE maf.

Idle question, but I have an ‘04...

Have you cleaned your idle control valve? This might clear up the occasional hesitation you say you are experiencing.

Not sure it has any effect on the running rich issue.... but you never know.


Sent from my iPhone using Tapatalk

I haven't, yet. But sure it's worh a try!

[fernando306]

Guys,

I have a super chinese knock off MAF, like those $20 bucks from Amazon.
Would like to replace it. Do I need the GENUINE BMW, or this VDO from FCPEuro would do the trick?

https://www.fcpeuro.com/products/bmw...566983#reviews

[Muzz258]

VDO is a good MAF.

[Muzz258]

As an after thought, When you get the new MAF, redo the test on it. I'm happy to plot the results on the same graph to see if there is a change.

[fernando306]

As an after thought, When you get the new MAF, redo the test on it. I'm happy to plot the results on the same graph to see if there is a change.

Great. I've placed the order, and I'll report back as soon as I put it back in the car. I really hope it fixes the awkward throttle response.
I'll be happy to redo the test, thanks for graphing it. I hope the new one looks more linear.

[Muzz258]

Hi,

Did you ever get the new MAF fitted? I've been doing a bit more MAF testing lately and need a good set of M54B30 New MAF test results to validate some assumptions. Trying to get a process and expected results that I can share on the forums.

I have found that the best test results come from a Scanner with some sort of Logger. The OBD Fusion smart phone app works well. I have also been including the 4 fuel trims in my logging as this help validate the MAF data.

If you have some test results that you could share, that would be great.

Regards

Murray

[colb]

No one has mentioned a vaccum leak as a cause for rich/high fuel trims, despite the suspicion pointing towards the Chinese Maf as a cause it would be worthwhile searching for a vaccum leak across the engine between the Maf and the exhaust. Leaks anywhere within the system will result in high fuel trims as the car tries to richen the mixture to compensate what it sees as a lean mixture due to the extra air the exhaust sensors are seeing. The car will add up to 20% more fuek to richen the mixture before giving up and setting an EML on the dash. If you cannot find any air leaks visually then I would reccomend a smoke test which will search out any leaks and ID them for you. When smoke testing you will need to look all over the engine checking out all inlet and vaccum rubbers and pipes including all the plastic pipes and their joints on the CCV system. Pay particular attention to the dipstick hole if you have one, the rubber O ring in there fails. Also give the plastic valve cover a good look over for smoke, had a mates car with high fuel trims and that turned out to be cracks in the plastic valve cover. Would not have found that without smoke testing.