Ok fellas, here we go. I am having some serious hesitation issues with my 04 wrx with 67k miles. When I get out of vacuum and into boost, it feels like Im pulling a trailer. I hit full boost and I go nowhere. It used to only happen a lil, now it happens 90% of the time, in every gear. Sometimes it won't happen and it will pull hard and normal. Here is the history:
Car had a TBE for about a year running stock boost..zero issues
Car was demodded and ran full stock for about 6 months..zero issues
A week before deciding to keep her, I feel a TINY bit of hesitation under full boost
A week later, I put the TBE back on..problem worsens slightly
Over the course of the past month, it has gotten bad.. to the point where sometimes a few backfires come out of the exhaust.
No CELs at all this entire time. No smoke whatsoever. No funny smells. No oil in coolant. I have, however, noticed a different noise coming from my fuel pressure regulator. When I turn the key and the fuel pump primes, a "swoosh/light gurgle" comes from the FPR. I put my finger on it and can feel it moving in union with the noise. Now here's the thing, I can't remember if it did that before. I don't ever remember hearing it like that.
What I've done so far:
Changed plugs to BKR6Es
Visually checked coilpacks and they look perfect
Did a compression test. Results: 155, 155, 155, 160
New vac lines to from turbo to BC to WG actuator
Checked stock BPV, perfect..zero leaks.
Replaced air filter
Cleaned MAF thoroughly and cautiously
Visually checked intercooler, looks fine.
Removed and reinstalled intercooler, making sure that every harness, clamp, etc.. was perfect.
Visually checked turbo inlet and BPV return hose..look fine
Ran through 3 tankfulls of 93 Octane gas, zero issues with gas
Checked grounding points..all tight and clean
Looked at the FPR..no leaks..no smell of gasoline, clean connections
What I haven't done/suspect:
I havent done a pressure test
I havent done a leakdown test (really dont think I need to)
I havent checked the injectors (they are stock and have never been touched)
I havent checked the fuel pump (my biggest suspect right now)
Now, I know some may say I need a tune, but I ran like this for a long time without issues. I do need a tune and will be getting one soon, but I need to resolve this issue before then. This problem only happens when I enter boost. At 0psi and vacuum, the car is perfect. In second gear I can get it to break out of hesitating by getting off the gas and back on a lil, then it seems to push past the hesitation and pulls free and hard. It idles like a charm and when it doesn't hesitate, it runs super smooth. If i can think of anything else, Ill post up right away.