Cocktail of 3.0i Trouble Codes - Where to Begin?
 

Hey all, hope you're well. I had a P1093 code on my X5 for many months. That's the pre-cat fuel trim too rich code. I replaced both pre-cat oxygen sensors and set of spark plugs with no resolution.

I read several posts about a faulty idle control valve being the source of this problem, so I installed a brand new one in a desperate attempt to clear the code. The original had 18X,XXX miles on it and was cleaned once before, so no harm in replacement at this mileage anyway.

Here's my current list of codes, where do I begin? Haha. Smoke tested the intake, no leaks found.

P0313
P0161
P1092
P0158
P0313 PD

Wondering if this is a bad bank 2 sensor 2 oxygen sensor.

Here's the car in question, out for a blizzard cruise the other week... https://youtu.be/5CFdYNxKsK4

Start with first code listed and work down.

Are you able to view live data? Short term, long term, 02 sensor voltage, MAF airflow in g/s. I wouldn't be changing the 02 sensor before seeing what kind of live data they are reporting.

Would you mind defining each code? I'd like to help, but I don't want to look them all up.

And I don't suppose you have a BMW-specific scanner? just P-codes?

Were all these codes there previously? or did they just pop up? Was it only P1093 previously?

Check MAF g/s values first. Should be in the 3 g/s at idle with no additional power draws, i.e.: no AC, lights, radio, blower fan, etc. 4g/s is too high

Secondly check your fuel pressure, should be around 52 PI Max.

Here are the BMW trouble codes using the C310 tool:

99 Oyxgen-sensor voltage behind cat converter, bank 2
EB Trimming, oxygen sensor before cat converter, bank 1
BF Insufficient heat output, oxygen sensor behind cat converter, bank 2
F3 Misfire, cylinder 6
F2 Misfire, cylinder 5

Checked out the other readings:

Idling the car with lights on last night, voltage at air-mass flow sensor 0.9 V

Air mass reading 18kg/h while idling
Air mass reading 44 kg/h at 2,000 rpm
Air mass reading 55 kg/h at 2,600 rpm


Finally, the oxygen sensors:

Bank 1 before cat: voltage 0.11 to 0.76 V
Bank 2 before cat: voltage 0.11 to 0.76 V
Bank 1 after cat: voltage 0.11 to 0.76 V
Bank 2 after cat: voltage frozen at 0.58 to 0.59 V

Voltage appears static at the bank 2 oxygen sensor after the cat, when it should be fluctuating up and down like the other 3.

Additional info from the data stream:

adaptation, mixture, additive bank 1: -0.11 ms
adaptation, mixture, additive bank 2: -0.02 ms
adaptation, mixture, bank 1 multiplicative: 5.8%
adaptation, mixture, bank 2 multiplicative: 6.9%

At your mileage, having done a smoke test, and with those codes. I'd replace all 4 o2 sensors as a matter of maintenance. You already did the fronts, do the rears. Reset adaptations and go from there.

Voltage should not be fluctuating wildly for 02 sensor after the cat. The fact that your 02 sensor is varying the voltage leads me to think you have a bad 02 sensor but at bank 1 not bank 2.

Also your MAF 18K/hour equates to 18,000/3600 = 5g/s. 5g/s at idle is kind of high so. If you look at the video I posted, my MAF g/s was 3.6g/s at 700 rpm.
I think your MAF is over-reporting the airflow through it and the computer is trying to compensate for this data pid. You can try cleaning the MAF with MAF cleaner, don't use carb cleaner and make sure it is dried before starting the engine. Don't buy a cheap MAF from eBay or Amazon. Better to go to a junkyard and buy a genuine Siemens MAF.

Thanks, I meant to edit this post. The voltage is actually pretty static for the after cat sensors. My mistake.

Bank 1 after cat: voltage is 0.75 to 0.76 V
Bank 2 after cat: voltage is 0.58 to 0.59 V

Interesting theory, as far as I know the MAF is original, now 188,000 miles.

The MAF has been cleaned recently as well, no change. Yes, used MAF cleaner!

The car's exhaust definitely smells rich. The coil packs are also original, except one that was replaced.

The M54 engine utilizes a "Hot Wire" in the MAF. Air passing through the MAF cools the "Hot Wire" and from the voltage that is used to keep the "Hot Wire" hot the computer can determine the amount of air rushing through the MAF. Like a light bulb, the "hot Wire" eventually starts to deteriorate until it fails. Since the "Hot wire" is not getting as hot as when it was new, the computer is just assuming that a lot of air is rushing through the MAF, so to accommodate this rush of air, the computer commands the injectors to provide additional fuel to the mixture.

I've finally replaced the MAF with a new VDO sensor from FCP here:

https://www.fcpeuro.com/products/bmw...em-13627567451

I'm not sure I really notice much of a drivability difference, maybe slightly better throttle response. But maybe that is all in my head lol.

Here are the updated readings with the new MAF installed:

15 kg/h at idle
35 kg/h at 2000 rpm
44 kg/h at 2500 rpm
57 kg/h at 3000 rpm

With the old, high mileage original MAF, the readings were:

18 kg/h at idle
44 kg/h at 2,000 rpm
55 kg/h at 2,600 rpm

I'll wait for the gurus to chime in as to how much of a difference that is... next step is to replace those post-cat oxygen sensors.

Post grams/second at idle with all accessories off. (lights, radio, AC/fan, etc). Should be hovering around 3.2 - 3.8 g/s

Remember that the MAF is measuring the density of the air, so temp, humidity and barometric pressure all play a role in trying to compare readings.

If the car sits outside, check for wires chewed by animals (squirrels etc.)...

Took the readings again tonight, with daytime running lights and radio off. Everything off.

14 kg/h at idle
32 kg/h at 2000 rpm
41 kg/h at 2500 rpm
55 kg/h at 3000 rpm

Seems to be driving fine, the one after-cat oxygen sensor says no signal so definitely going to replace both.

I'm going to say that based on the info above, the new MAF has not improved the cocktail of codes condition haha.

edited correction to the percentage
3.88 g/s. vs 5.00 g/s. difference 28%
8.88 g/s. vs. 12.22 g/s. difference 37%
11.38 g/s. vs. 15.27 g/s. difference. 34%
15.27 g/s

Yep must be something else. Data doesn't lie

You are comparing the wrong data sets actually. Keeping all other factors constant, I think we would want to compare the first numbers reported. Those were the before/after readings where the headlights were on both before and after the replacement.

The data shared yesterday with the headlights off cannot be accurately compared to the numbers with the old maf, where the headlights were on. It did end up making a difference in the readings with the daytime lights left on.

4.16 g/s at idle (new MAF) vs. 5 g/s at idle (old MAF) with the same conditions, engine warmed up and daytime running lights on.

If my math is correct that represents a 16.8% change. Not insignificant, but perhaps other factors such as temperature and barometric pressure can explain that?

Does anyone know if Bentley or BMW offers operating specs or range for a MAF?

Your math is incorrect. To go from 4.16 g/s to 5 g/s is a difference of 20.19%

I also get 16.8%?

5 - 4.16 = 0.84, 0.84 ÷ 5 = 0.168 × 100 = 16.8%

Been a while since I had to do this math, but I think using the initial value 0.84 / 4.16 gives you a 20.19% increase from 4.16 to 5.

Regardless, how that is interpreted is more important. Bentley manual offers nothing with respect to proper MAF flow readings or operating parameters.

Does anyone have something from BMW or VDO/Siemens to reference?

That would be correct if you are talking about going from 5 g/s to 4.16 g/s, but if the correct reading is going from 4.16 g/s to 5 g/s you will divide by 4.16 not 5.

We know that 4.16 g/s is closer to what the Value should be so we are looking at going from good to bad.

Here's a video showing what the MAF should be at idle as well as the 02 sensors. As you can see the MAF is below 5.0 g/s. This is a known good reading.

https://www.youtube.com/watch?v=zyh_4SktmFM

Gotcha. :thumbup:

You are chasing your tail with the MAF readings. There is no way to pin down a known good reading within a range that small because there are too many variables which is also why you won't find it in the service manual.

My "Known Good" is when I had my X and decided to make a video of what these parameters should be based on no Check Engine light and No pending code or active code in the DME.

Even differences in volumetric efficiency due to camshaft timing will throw a wrench into that.

It may or may not, but unless you just like throwing parts at a problem, you need to do some empirical diagnostic. Even Overboost thought that 5.0 g/s is way too much airflow at idle for an X. Should be along the order of 3 g/s which if you look at the video I posted my "Known Good" was 3.6 g/s.

https://xoutpost.com/1200056-post7.html