FIXED: Return of the P0171 and P0174
 

It is me again! So driving my beautiful X5 home last night, and the dreaded P0171 and P0174 popped back up, along with the same symptoms as last time. Loss of power, driving slow, the works.

I replaced the fuel rail, and fuel filter along with the fuel pump last time. I ordered a replacement fuel rail because I had broken the schraeder valve on the old one, from someone on ebay, so the part was used, I figured it wouldn't cause any problems. As for the fuel filter, a brand new MANN was put in. The fuel pump however was used from a dismantler. Now, I'm not saying the fuel pump was the best condition, but being as it was the issue last time, I am thinking the thing took a shit again. Before doing any of that though, I am going to review both the MAF sensor and the DISA valve (because let's face it, I need to diagnose this thing properly with the same diagnostics as last time), and the DISA was used, so I hope it isn't that. But, overall, a little bummed as my car usually doesn't have any problems.

Problem has been fixed:

Apparently, the vehicle had a kink/damaged fuel line from the fuel rail to the filter. The fuel line leak was causing the intermittent pressure issues, and the kink was causing the poor acceleration. the kink is fixed, but the line is damaged and needs replacing. Unfortunately, it is a special order part which takes anywhere between 1 week to a month to arrive through dealerships. I have since found the part needed (13537548988 on REALOEM) online at bmwminifactorydirect.com, but am waiting for them to ship it (Maybe it will take a while with them too) I spoke to the mechanic and asked if it was at risk of damage if running as is. He said there is no real threat as long as I don't drive heavily nor far. He recommended I stick to my 3 mile commute only until the part arrives for replacement. So for now, the vehicle is back 90%, just needs the hose, but runs great and has no other problems. Just wanted to give closure to some of you.

Adrian, trace your steps and see if anything got unplugged or chaffed - when you worked on something you may have moved wires, they might be touching somewhere that they should not...

keep us posted - we will pull you through... :thumbup:

What could possible be unplugged that is causing this? Everything was working good for a few weeks.

some of the BMW plugs are notorious for looking snuggly latched but in reality not fully engaged. over time, with engine vibration and road bumps, something may have come loose...

the other possibility, a wire that was once properly routed, was dislodged from its path and now is shorting to chassis or interrupting the line...

of course, there is a possibility that items that you have replaced may have failed again - i recently replaced a collant tank that was leaking at the seams with a spanking brand new OE tank from a dealer, just to find couple of days ago that the new MF!!! is leaking at the same seams... and that was a virgin original tank!!! of course i will replace the newly leaking tank, but WTF?!, i bought that new tank in May, and less than 3 months later it is pissing my coolant away!!!!

So what could I possible start looking for? MAF sensor plug, DISA valve plug, fuel pump plug, fuel injector plugs?

you are correct, those are the things that you worked on, and would be a good thing to start...

the car is in distress all the times now, or the problem comes and goes?

Well I was driving it, and all of a sudden I lost power. if I gently pushed on the gas pedal it would accelerate steadily, and I could go up to 55-65mph, but it slowly started losing power to the point where it gave me a light (the yellow cog) and I got the pending P1071, P1074 codes. I turned the car off, turned it on, and it turned on just fine. I gave it gas and it gave me great RPMs, then slowly, started doing the same thing, and chocking when I would floor the gas.

tell us more about the moment when it goes from normal to bad - you said gradually it loses power? or, there is an event, like you try to overtake traffic, like merging, or you turn on AC and then something happens...

you should be able to retrace your footsteps rather faster this time, as you already know where the MAF is, how DISA looks like and if the fuel pump is working or not... i sure hope it is one of the older things that you did last time, as opposed to something new acting up...

and hopefully we will have folks with more expreience with juicy parts chime in as well

Rent the fuel pressure gauge and connect it to the engine when the engine is losing power again and check the fuel pressure. This time don't crank on it so hard that you end up breaking the shraeder valve housing. Have a fire extinguisher handy just in case.

Well I basically came to a complete stop at a stop sign, and as my usual lead footed self :dunno: I accelerated to continue on my way, but I felt the car strained. I turned on Torque on my dash and saw that the engine load was at 60% with 2k rpms, not normal. It seemed like if I layed off the gas and gently pushed on it, it would accelerate slowly, but steadily. If I floored it, it would stay at the same low speed and kinda stutter. The A/C hasn't been used since I got it running again because it went bad (I had another thread about that)