Boost jumping from 22-18 back and forth

[justinh722]

I recently turned my boost up to 22 psi and now the boost is jumping. The needle will literally move from 22, then to 18 and then back to 22 and then to 18 and so forth. I can hear the turbo doing it so I know it's not a faulty gauge. MAP sensor reads the jump also.

I just recently set the actuator on the wastegate but at 17 psi, it held steady. I made it so I had to give it a little tug to get the arm on the actuator so It would hold it shut properly. Did a boost leak test and I only have a small leak at the throttle shaft seal that I just recently replaced with a seal I had off another TB. This seal doesn't leak nearly as bad. I'm running a 16g turbo. I'm wondering if the wastegate needs ported or if maybe my MBC is causing it. I have the stock size down pipe and I noticed a small crack on the top of the manifold that I could only feel leaking when cold. Any suggestions?

 

[dsm144]

Sounds to me like you have to many leaks to even count

 

[justinh722]

Too many what? Exhaust leaks? I have only 1 exhaust leak and a tiny air leak. I don't see them causing my symptoms.

 

[dsmrebel084]

It sounds like you have a major leak somewhere. Try and double check everything you looked over.

 

[NOSLO2PT0]

Could be some small compressor surge, but that's difficult to do with a 16G.

 

[justinh722]

Could it be my BOV leaking at high boost? I have a Greddy Type RS and I did the single spring mod to it. Maybe I'll put the other spring back in or is it possible to stretch the spring that's in it to make it stiffer? I'll do a run with the other spring in and see what happens.

 

[phunny]

Have you done a boost leak test

 

[justinh722]

Yea it's all in the original post. I checked for boost leaks once again, it's only coming from the throttle shaft seals. I was able to get the boost up to 20 with the air compressor and it was leaking from the seal. Can a throttle shaft seal leak cause this? I'm gonna try the spring out tomorrow.

 

[Nasty Dream]

Have you tried running less boost (14?), see if it sticks better? Just for testing at least.

I think it's possible the adjustment screw is a bit loose in the boost controller. Maybe you are a little further out than it is designed.

You are trying to run 17 PSI?

You should get rid of leaks. Sounds like you've got an exhaust leak which sounds like is causing boost creep, an air leak sounds causing boost leak, and who knows what else.

That sucks. It's possible to patch those up so you don't need to replace.

 

[Lofty]

I had a cracked turbo around the wastegate pull the same symptoms, just another extra tip!

 

[russell3123]

stock 16g wastegate should be fine for anything under 25psi. i would check the brake booster line for dry rot .. every one overlooks it