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I have a '01 Beetle Sport with a 1.8T. I am getting a P0171 code. I repaired the cracked power brake booster line and the cracked/soft PCV line. I have checked for other vacuum leaks with a hose attached to a stethiscope. The only thing that shows up is a pressure leak where the PCV line attaches to the lower block (I can hear pulsing from this area). Would this be enough to set a P0171 code?
 

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Anything, is possible, any vacuum leaks should be repaired and bad hoses, parts replaced (then, after the repairs; recheck your fuel trim levels); do you have a scan tool and can you view live data?


As noted, in the Ross Tech Wiki; there is a long list of possibilities, have you checked your fuel trims (+ or - 10% being considered in the normal range), MAF readings and done a fuel pressure test? These are defintiely; the common causes and tests can be done yourself, to rule these possibilities off of your list (process of elimination):



fuel pressure testing:


Vacuum leaks are common on the 1.8T; a smoke test or other methods can be a way to find leaks. At almost 19 years old; we are seeing, many 1.8T new beetle's with weak fuel pumps and they can throw a lean code but not much else (a bad fuel pump; will not throw a code, aside from a lean code or if the fuel pump relay is failing, one for that).

Most auto parts stores; will have a fuel pressure test kit, available for free rental and it is not hard to perform this test. Give us some more info; on the history of the car, how it is running and the results of your repairs, testing... we can go from there. Thanks.
 

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Thanks for the response. I had a better look at the crankcase breather elbow and can see that it is cracked, so I'll order a new one. While I'm waiting, I'll check the fuel pressure and the fuel trim numbers. (I was going to check the fuel trim last week. but I didn't feel that it would be safe to looking at the scanner while driving in bad weather.)
As far as how the car runs, it seems to run perfect. I just get the CEL that turns on. I can clear the code (P0171 is the only fault) and it will come back within 2 days. As far as previous history, I'm afraid that I'm not much help there. I just bought the car last winter, as a wreck, and just put it on the road this spring.
Thanks again and I'll post more results when I get them.
 

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OK, here are some results: I replaced the cracked crankcase vent elbow, as well as the dipstick tube that broke while replacing the elbow. I hooked up my scanner and drove it. A test of the Mass Airflow sensor(WOT @ redline) showed approx. 135g/s after I did the math to convert it from lbs/min that my scanner reads(which seems good). After driving approx. 50 miles home, my Long Term Fuel Trim had crept up to 21.3%. Short Term Fuel Trim was fluxuating around -3% to +10% depending on weather I was accelerating, decelerating or holding steady. I hooked up a fuel pressure guage today and had 35psi at an idle. The pressure would respond to vacuum changes when I reved the engine(psi raised when opening the throttle, dropped when throttle was released (which seems good).
My next step is to build a smoke tester and see what my results are.
 
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