Cfarris87

Hey guys, I'm having some pretty bad boost issues and thought I'd try here first before throwing a ton of cash for diagnostic fees etc. I just replaced the turbo inlet pipe because it was collapsing under boost but I'm still having some issues. Under accelleration once boost is built it has a lot of stuttering/popping above about 15 psi and then kicks into limp mode until you let off and completely spool down. Also boost will build up to 23-25 psi very frequently, which is very scary for a motor with 190,000 miles (tuned to 18). I'm not too familiar with the turbo systems in these cars and haven't seen anything online that really matches up with my current problems. Could it be a wastegate or n75 isuue? Any help would be GREATLY appreciated. I just bought a FR-S and really need to get this car up for sale. Thanks!
Hopefully you can kind of tell what's going on in these.

Cfarris87

Bump, anyone?

roadyTT

How's your MAF? Pretty old?

Power5

Blowoff or recirc? I tried putting a blowoff on mine so many years ago, but car always went to safe mode because it did not see the air that was blown off. So long ago that I don't remember exactly how it acted, but I had to turn off the car and turn it back on to get it to go to regular boost again.

iflywoe

did you run the lines and see if theres a leak?

Shomare

Does the turbo have lots of power still or does it feel gutless (gutless could be bad turbo)? Smoking any (bad turbo, might be able to be rebuilt with factory kit)? Does the car have no power off the line and then hammer hard all of a sudden when boost is high (pressure and vacuum leaks can cause this, use a smoker at very low pressure to find them, and bump up pressure slowly as you fix the leaks)? Does it feel good but drop power at near full boost (could be bad recirculation valve, get the 71 model for cheap or go nuts and get a custom one, but the 71's are more than fine for stage 1)? Any high pitched squealing noises under boost (bad turbo, and the spindle and fins are probably running out and hitting the exhaust housing portion of the turbo)?

Have you had anyone check the car with a vagcom type setup to see if it has triggered any codes, those are extremely helpful and key in your troubleshooting. I bought the Ross-Tech vagcom adapter for $250 so I can consistently monitor my car for problems since I am keeping the car long term.

Let us know

Mister Bally

If that is your original turbocharger, I would suspect it. Remove and have your original rebuilt by a reputable shop if you are keeping the car long term.

If you were to take the car to an Audi dealer, the diagnosis would be "Replace turbocharger" due to the issue you are having along with the mileage.