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New to forum. Read lots of posts and unfortunately learned of PD cam lobe problems. 2004 Jetta TDI BEW. 140000 miles. Oil change with Castrol synthetic formulated for VW diesels at 7500 oci. p0101 code from Advance Auto generic code reader about 4 months ago. Replaced MAF. Code came back after about 500 miles. Started having intermittent black smoke and sound. From youtube video found here, sounds similar to "bupping" noise but I am confused that the noise will vary from undetectable throughout rpm range to a noise similar in video, especially at about 3500 rpm. Will pull valve cover off this weekend. Parked it until cam is checked. Is it possible to have varying levels of noise from cam wear?
 

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Observations of these particular symptoms if this is helpful for the forum: Commute on interstate 75 miles one way with 2 toll booths. At first toll after 20 minutes no detectable noise/no smoke during acceleration. 20 minutes later at the second toll, could hear engine noise as slowly drove thru toll and then cloud of black smoke during acceleration with whiffs of smoke at cruising speed/throttle change. In driveway, could gradually raise rpm to 3500 or so and after about 20 seconds sound would subside and essentially no smoke. The noise and smoke becoming more persistent over last 2000 miles until now. As soon as weather quickly turned to 80s and higher humidity, the smoking problem seemed to be more persistent. Temperatures cooled back to the low 60s for a week and sound/smoke largely subsided. Early on, can the ECU attempt to compensate for wear/valve lift and do so under relatively cooler engine conditions? In hindsight I should have suspected the cam much sooner---intermittent sound threw me off.

Since I ran it for awhile with noise, could the exhaust back pressure, bupping sound, cause damage to variable intake flaps, if it has them. Is there a procedure to check them?

Thanks very much for the informative writeup and videos for timing belt and cam inspection/replacement.
 
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