P0171 P0174 Check Engine Light CEL

[JPuma]

Originally Posted by racebmwm3

Not sure if you’ve measured continuity in these wires but this is what I got:

Wires 1 & 2: 4.669 kOhms
Wires 2 & 3: 10.58 kOhms
Wires 1 & 3: 3.763 kOhms

I havent, but I think the issue there is just worn pins not making good conductivity, or possibly the crimped wire strands in the insulated wire breaking over wear and tear. A video I watched of one user sources his problem to bad connectivity in the connection plugged into the DME. I've check and cleaning mine on that side too.

[JPuma]

Originally Posted by andrewwynn

Is that the measurement off the MAF?


Sent from my iPhone using Tapatalk Pro

After racebmwm3 posted the stats of each MAF he tried I decided to circle back on the used OE MAF I bought to retest since replacing the wire seems to fix some issues for me. I had a newly purchased MAF from VDO in since 2019, but before that I bought a used Siemens MAF because I broke my original one (oops). I was skeptical the used OE MAF wasn't working right because of wire issue.

My fuel trims are amazing now after the normal test drive I take. My car doesn't vibrate as much which is another issue I have. Can be a placebo to me so ill keep an eye on that. Was planning on replacing my motor mounts because of this vibration.



Up next is a piston soaking, just waiting for ACDelco additive. Going to check my pressure before and after. Will make a new post for that soon.

[racebmwm3]

Originally Posted by andrewwynn

Is that the measurement off the MAF?


Sent from my iPhone using Tapatalk Pro

Measurement on the harness. But you’re right, I should probably measure the MAF as well.

[racebmwm3]

Update:
Got the Amazon MAF and installed, but doesn't seem to have changed the situation. New MAF reading similar to old MAF.

I still cannot get decent fuel trims. I disconnected the battery to try to reset everything, but I am still not getting proper fuel trims. Things mostly fluctuate but have never been within the right ranges.

The last time I tried testing, I was getting STFT Bank 2, then both STFT pegged at exactly 15.60, then they dropped to both negative after some time.

Still throwing CEL.

I am totally stumped at this issue. Not sure what to try next.

[JPuma]

Originally Posted by racebmwm3

Update:
Got the Amazon MAF and installed, but doesn't seem to have changed the situation. New MAF reading similar to old MAF.

I still cannot get decent fuel trims. I disconnected the battery to try to reset everything, but I am still not getting proper fuel trims. Things mostly fluctuate but have never been within the right ranges.

The last time I tried testing, I was getting STFT Bank 2, then both STFT pegged at exactly 15.60, then they dropped to both negative after some time.

Still throwing CEL.

I am totally stumped at this issue. Not sure what to try next.

If MAF looks good, check your fuel pressure, I think you mentioned you did. how's injectors?

What is your LTFT at idle after warming up. Do you have a tool to clear your adaptations? when you pulled your battery and tried again did LTFT clear and start at 0.0?


BMW_E39_Oxygen_Sensor_And_Fuel Trim[1].pdf

[racebmwm3]

Originally Posted by JPuma

If MAF looks good, check your fuel pressure, I think you mentioned you did. how's injectors?

What is your LTFT at idle after warming up. Do you have a tool to clear your adaptations? when you pulled your battery and tried again did LTFT clear and start at 0.0?


Attachment 83659

No idea how to tell if the injectors are bad or not. Fuel pressure was tested in Post #1

I pulled the battery, shouldn't that clear everything?

I did clear everything with the ODBII tool as well, or I thought I did.

LTFT's after some testing were 11.70
STFT's were running all negative

https://share.icloud.com/photos/0ffZ...1uBE86opDALUBA

[JPuma]

Originally Posted by racebmwm3

No idea how to tell if the injectors are bad or not. Fuel pressure was tested in Post #1

I pulled the battery, shouldn't that clear everything?

I did clear everything with the ODBII tool as well, or I thought I did.

LTFT's after some testing were 11.70
STFT's were running all negative

https://share.icloud.com/photos/0ffZ...1uBE86opDALUBA

I don't think pulling the battery will clear the adaptations. I use INPA. Your LTFT is suggesting you have a big air leak or bad gas flow. Driving or letting it run should adjust it over time if the MAF was an issue, but it doesn't look like changing the MAF had an effect.

https://www.bimmerfest.com/threads/a...-values.39418/

Did you check the back the of the intake manifold, there is a rubber going over a vacuum port. Then a small hose going to secondary air. How's the rubber boot and the little arm attached to it? How about CCV? or the vent hoses going to CCV? Top one from valve cover?

[racebmwm3]

Originally Posted by JPuma

I don't think pulling the battery will clear the adaptations. I use INPA. Your LTFT is suggesting you have a big air leak or bad gas flow. Driving or letting it run should adjust it over time if the MAF was an issue, but it doesn't look like changing the MAF had an effect.

https://www.bimmerfest.com/threads/a...-values.39418/

Did you check the back the of the intake manifold, there is a rubber going over a vacuum port. Then a small hose going to secondary air. How's the rubber boot and the little arm attached to it? How about CCV? or the vent hoses going to CCV? Top one from valve cover?

I smoke tested multiple times. Didn’t see anything leaking anywhere. Rubber nipple under back of intake is fine. CCV is good. Replaced whole system couple years ago with updated version. I’m not sure what you’re referring to regarding small hose, rubber boot and little arm. Hmmm

[andrewwynn]

Smoke test was done on intake. I think also on valve cover (If not do so).

A very sneaky vacuum leak is where the oil dipstick tube goes into the engine block.

My gut is saying that something is amiss with FPR. It uses vacuum from intake as feedback loop to drop actual fuel pressure when there's high vacuum. If that's not working properly the fuel pressure may drop too much. Also I've never seen over 50.5 at idle so the numbers you reported seem way too high.

That said, if the fuel pressure is high and your still are getting positives fuel trim it suggests the injectors.

You can remove and clean old school injectors. Some shops will do this service. The cleaning machine will have clear walls to see the injector spray.

[racebmwm3]

Originally Posted by andrewwynn

Smoke test was done on intake. I think also on valve cover (If not do so).

A very sneaky vacuum leak is where the oil dipstick tube goes into the engine block.

My gut is saying that something is amiss with FPR. It uses vacuum from intake as feedback loop to drop actual fuel pressure when there's high vacuum. If that's not working properly the fuel pressure may drop too much. Also I've never seen over 50.5 at idle so the numbers you reported seem way too high.

That said, if the fuel pressure is high and your still are getting positives fuel trim it suggests the injectors.

You can remove and clean old school injectors. Some shops will do this service. The cleaning machine will have clear walls to see the injector spray.

Yep I smoked tested everything. No smoke coming from anywhere. Removing the oil cap during the test released pressure and smoke so I know I was doing something right. I pulled the dipstick when I was smoke testing and I could hear the pressure release up thru the oil. No smoke was escaping anywhere. CCV is relatively new. All good hoses. No leaks.

I’ve just figured out how to reset adaptations on my scanner. Resetting things brought the LTFT to 0. STFT started high but are coming down as I sit here and idle.

https://share.icloud.com/photos/039L...1b7Mu4Ur_00DNw