Hey guys, a quick question. I'm getting the infamous P0171 code, and while checking for a vacuum leak I ran across something puzzling. There's a short line that I suspect is a vacuum line, but it doesn't appear to be listed on the little diagram under the hood. It runs from the intake manifold to the end of the fuel rail, where it plugs into some round component held on with a clip of some sort. The line is fastened with some kind of single-use crimp clamps, which is why I'm not sure if it's a vacuum line or what (since none of the others appear to be held together that way). It's got a braided cover which is cracked. Is this really a vacuum line, and if so can I just replace it with some standard tubing, or is it something else? I guess it's time to bite the bullet and order the Bentley manual...

 

That would be your FPR, which sees boost and vac. Yes you can just replace it with a normal clamp set and normal hose

 

^what he said. FPR stands for Fuel Pressure Regulator. It uses the boost/vac signal from that vac line to decide how much fuel to let out of the fuel rail for your injectors.

 

Look around for all of that tubing - more may be cracked - and replace it with silicone hose. The small tubing is 3.5mm. There are lots of places you can buy the hose from but I got mine from https://www.hosetechniques.com/

 

Yeah, it's interesting: while poking around under the hood, I noticed that it's *really* clean under there, and there appear to be several recently-replaced parts. I'm wondering if the PO was really good about keeping up with maintenance, or if the P0171 has been going on for awhile and there have been some previous attempts to fix it. Anybody know how to score a Carfax report?

Think I'll pay attention to dragonrage and score some vacuum tubing and start wholesale replacement of anything that looks vintage.

 

Fwiw, when I had this code it ended up being a bad MAF.

 

The MAF may be one of the new-looking parts, but I'm not sure (just ordered the service manual last night, once I get it I'll know what I'm looking at under there!). I'm keeping it in mind, though. I think the usual suspects are vacuum lines, MAF, O2 sensor and fuel filter, so I'm checking them out in increasing order of price

 

Ya I did the same thing, start cheap when you can, just letting you know that can also be a culprit.

 

Sorry for this most basic question, but when you find whatever is the culprit for the CEL, does the light go off or do you need to have some tool like VAGCOM to turn it off?

The reason I ask is that my CEL just popped on, two days after I finished replacing the CC breather system. I may have a vacuum leak, because I noticed that a lot of my hoses were really brittle, and I may have pushed them over the edge during the breather replacement.

 

I had a CEL for a week or so that spontaneously went away, so I'm guessing once you fix the problem the light will go out. I suppose there could be some errors (emission-related, maybe?) that would require someone to explicitly reset them. FWIW, when I read my codes, my CEL went out. I'm guessing the code reader did it automagically.