FIXED: Return of the P0171 and P0174 - Page 28

sunny5280 · #1 09-10-2013, 05:14 PM

Quote:

Originally Posted by diddy0071

I hope you're kidding. The tail light just went out a few weeks ago.

Yes, I am kidding.

bcredliner · #2 09-10-2013, 06:05 PM

Here is an example of a conclusive MAF test. How To Test A Bosch MAF Sensor - YouTube

The test of unplugging the MAF is an indication, not a sure thing. This test indicates a bad MAF if the engine smoothes out when the MAF is unplugged. This test is only applicable at an idle, has nothing to do with how the engine runs when taching it up.

bcredliner · #3 09-10-2013, 06:26 PM

Regarding the bad cat suggestion some of your symptoms, like the bogging are similar to a bad cat. Many times if you get under the X listen or jiggle them a bad cat will rattle. My experience has been that the are either good or bad, they are not intermittent or change based on going or coming from work.

bcredliner · #4 09-10-2013, 06:44 PM

Regarding vacuum leak suggestions. There have been times when I have gone over the same possibilities looking for a vacuum leak and concluded there was none, checked everything else that I could be sure of and ultimately went back looking and finding a vacuum leak. I never know when I have done enough to be sure there is no vacuum leak. I am not saying you were not thorough.

bcredliner · #5 09-10-2013, 07:23 PM

One of the posts you made earlier today was referencing your video--the engine was running fine. In the video you said you had not tried hard acceleration--do you know if it ran fine under hard acceleration as well?

diddy0071 · #6 09-10-2013, 07:32 PM

Quote:

Originally Posted by bcredliner

One of the posts you made earlier today was referencing your video--the engine was running fine. In the video you said you had not tried hard acceleration--do you know if it ran fine under hard acceleration as well?

it runs fine if I slowly accelerate. if I push too hard on the pedal, it bogs.

upallnight · #7 09-11-2013, 08:17 AM

It's bogging down when you mash on the accelerator because according to the video with the gauge at the fuel rail, the pressure in the rail is going down. For some reason the pressure is going down when you mash or snap rev the throttle. The pressure should increase about 5 psi when you mash or snap rev the throttle.

I would check the vacuum line from the fuel regulator to the f connector at the intake boot. If that checks out with no leak, get a vacuum gauge, remove the line to the fuel regulator and connect the vacuum gauge and see what type of vacuum you get when the engine is at idle and what type of vacuum is present when you mash or snap rev the throttle. The vacuum should go down when the throttle is snapped rev or mash. If everything checks out then you may have a clogged fuel filter.

You can also check the fuel pressure at the rail and then remove the vacuum line to the fuel regulator either at the regulator, or at the F connector in the intake boot. The pressure should go up. If it doesn't you may have a bad fuel regulator.

bmwven · #8 09-11-2013, 08:42 AM

Maybe you are loosing fuel pressure at the fuel transfer system. Check or replace the O-Ring No. 4 in the dwg. and verify again fuel pressure

upallnight · #9 09-11-2013, 09:34 AM

Quote:

Originally Posted by bmwven

Maybe you are loosing fuel pressure at the fuel transfer system. Check or replace the O-Ring No. 4 in the dwg. and verify again fuel pressure

That fuel transfer has nothing to do with the fuel pressure in the fuel rail. That transfer is used to move fuel from the left side of the tank to the right side of the tank where the fuel pump is located. A bad fuel transfer will cause the engine to die/stall from a lack of fuel because the fuel sender is on the left side and the fuel pump is on the right side and if the fuel doesn't get transfer the fuel gauge will still read full but there is no gas in the fuel pump sump.

bmwven · #10 09-12-2013, 02:10 PM

Quote:

Originally Posted by upallnight

That fuel transfer has nothing to do with the fuel pressure in the fuel rail. That transfer is used to move fuel from the left side of the tank to the right side of the tank where the fuel pump is located. A bad fuel transfer will cause the engine to die/stall from a lack of fuel because the fuel sender is on the left side and the fuel pump is on the right side and if the fuel doesn't get transfer the fuel gauge will still read full but there is no gas in the fuel pump sump.

I disagree, there is a check valve inside the fuel transfer system that also acts as a regulator with impact on the fuel filter/regulator itself. The o.ring inside is so easy and cheap to change that if I were diddy0071 I will give a try