Help! Lots of shuddering before boost!

Posts specific to the 2.0 litre Turbo engine

Help! Lots of shuddering before boost!

Postby Hurstie » Sun May 29, 2022 7:35 pm

So, i recently purchased a 2004 subaru liberty GT. the second one i have owned. the only modifications the car has are a AVO catback exhaust. i was told that it had been "tuned" however there is no paperwork and have no idea.

the problem i am running into is that at low rpm (1250-2500rpms) i have lots of shuddering, jerking, hesitation etc. The higher the gear the worse it is, and the more load the car is under inside that rev range the worse it is. once boost hits ~2500 to 3000 rpm it drives extremely smoothly with no faults. On idle it seems to be a little rough and almost sounds like it doesnt have equal length header.

i have replaced the spark plugs, cleaned all the grounds and the coil packs, used some upper cylinder cleaner in the intake manifold and ive still had no luck. fuel economy seems to be fine and nothing out of the ordinary, roughly 450 - 500 kms to a tank of 98 (mostly city and some highway).

I have no idea whats going on and ive been scouring forums trying to find a solution.

if someone could PLEASE help me i would appreciate it greatly.
Last edited by Hurstie on Wed Jun 01, 2022 12:06 pm, edited 1 time in total.
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Re: Help! Lost of shuddering before boost!

Postby Hurstie » Wed Jun 01, 2022 12:05 pm

Update:

I have just replaced the in tank fuel filter however still no change. No engine codes showing up current or history. If you drive over 2500 rpm through all gears it’s fine, however it does seem like it may be a little down on power up high. I have smoke tested for vacuum leaks and there is none anywhere. I am going in for a power run and diagnosis tomorrow so hopefully some good will come out of that. Again I am absolutely clueless to what is going on, so any help would be greatly appreciated.
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Re: Help! Lots of shuddering before boost!

Postby bigBADbenny » Wed Jun 01, 2022 6:45 pm

Potentially an avcs fault, dirty maf or throttlebody issue.

They’ll see the avcs vvt angles when they log the dyno run.

Try the google this forum link with those keywords respectively…

Hmu if you need more help. Can health check in Melbs.
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