Very random overboost.

The vacuum can is in good condition and adjusted properly. About two months ago I went into limo mode, and it was from overboost. I believe the vanes are slightly sticky. I started to drive more aggressively and it seems to have gone away for a couple months. Took several 1000 mile round trips. Car was running like a top doing 70-100mph on a 800-1000 mile trip this past weekend. On my way back home I felt it go i to limp while accelerating in 3rd in a traffic slowdown. Restarted the car and was fine for the rest of the 160 miles back. My question is what is causing this very random and far spaced out overboost. I could drive aggressively now for two thousand miles and it could be perfect and then boom. It happens. 2002 Golf tdi.

This happens to me too on occasion. Yours does sound like sticky vanes. My maf has a faulty clip so I slide it on as tightly as I can and it usually works. I dont throw codes just loose boost for a time, then back to normal.

What can I do? Italian tune up.

Italian tune up is preventative. I do it whenever possible. I was going nuts with that technique since I didn’t want to buy a new turbo. Then I got some unwanted recognition for my driving habits and decided to sprayed easy off into the exhaust side of the turbo and that made it so I could get up hills but I still got overboost so I replaced the thing. Getting under the car to spray skin melting chemicals is not fun, and it might not work.

Mine literally has only been doing it once every 3 months for the past 6 months. I drive all through the white mountains with no problems. Wasn’t til I got back to Connecticut on flat ground in traffic that it did it.

This could be vacuum related. Check each component and the booster hose for leaks.

Watch doing Italian tunes if you are frequently overboosting.

my 01 was over boosting due to sticky vanes. We were on vacation in Texas on long rolling hills doing 70 mph. It did it 3 times in one day and once on a really steep hill. When i got home a few weeks after, i decided to do an Italian tune up. I down shifted into 3rd and stepped into it, then my IC blew the bottom off when it spooled up. Exciting stuff. i removed the down pipe and used seafoam. Then worked the actuator lever by hand until it didnt stick anymore. Worked for almost 1 yr. I just did an tune up a few weeks ago and went into limp. this was at 4000 rpms in 3rd for prolonged period of time.

FYI

Just did the Seafoam cleaning to the 01 Golf over the weekend. The car is boosting fine again. Its a little smokey till the Seafoam burns off.

Most of the time, it will end up needing a new turbo if you cannot get it cleaned out. Driving the car "spirited" often will prevent it from ever happening in the first place.

Another, less common, but possible, is an N75 valve that is not able to release vacuum quick enough due to debris inside, but that is usually from a rusted out VNT actuator.

I had a weird thing a month or so ago... I kept getting over boost and although the nut on the actuator arm needed a wrench to loosen it, I lengthen it a couple of turns and the problem went away. I still have the occasional over boost/cough but it usually only happens when the engine is not warmed up to operating temp.