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Resolved Boost Oscillating

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CollinClay

Probationary Member
15
1
Jun 19, 2015
Anchorage, Alaska
Hey everyone, first post so hi to all. I've been searching the threads for this issue and haven't quite pinned it down yet....I recently bought a super clean 90 tsi that had been parked for the past six years, it had a new head, new turbo and a few sensors in order to get it running good enough to buy. Anyway I followed the maintenance guide and free mod page, completed everything, did a full tune up, checks on everything, found a ton of issues that I have mostly resolved except one...under WOT the turbo sounds like its oscillating or wavering, we we we we we we according the dummy boost gauge it also twitches between 8-10psi. It pulls fairly hard but it also won't climb above 5200rpm. Looking for any suggestions or knowledge...thanks!!
 
I would recommend:
  • Complete a boost leak test:
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  • If all checks out, I would inspect the compressor wheel for damage around the edges (hitting compressor housing), excessive in/out play, and excessive side-to-side play.

  • If all looks good on the compressor side, turn to the waste gate. Check to see if it sticks and check for proper operation of the actuator. You may also need to pull the o2 housing to inspect the flapper.
 
Do you have any mods to the boost controller? i had a problem with my car when i installed a boost controller and when i pushed to full throttle the car would boost and as soon as the gauge hit 9psi it would waver back and forth as if the turbo would boost then stop,boost then stop almost as if it was turning on then off. turned out to be that the boost was turned to high and the waste gate was cracking open and closing do to being adjusted wrong. try driving around and only go half throttle to 3/4 if it does not waver again then its probably just a fine tuning issue. hope this helps keep us posted
 
Ya that's what mine is doing. I'm currently waiting to do my pressure tests due to lack of funds, but the car only does it above 8-9 psi (according to the dummy gauge) its a stock setup minus the little restrictor i pulled out of the stock boost solenoid controller. I'm not sure how to adjust the wastegate or recirc valve yet so I'll read up. Now that I think about it the Wastegate is a tad noisy, Im guessing you probably shouldn't hear it at all.
 
Yup, won't even hold 1 psi, passing right through the recirc valve. I tried crushing it to help, which it did temporarily but opened up new problems so I'll put a new valve on and test again. Thanks for all the input!
 
Fixed!...well the boost leak anyway... The little pressure tester is a great tool, I've used it a few times. Thanks again!
 
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