2006 WRX underboost issue
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This is a discussion on 2006 WRX underboost issue within the General Maintenance, Troubleshooting & Accidents. forums, part of the Tech & Modifying & General Repairs category; Hey everyone! I first want to start off by saying this is my first time posting on this forum and ...

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    Aug 2015

    2006 WRX underboost issue

    Hey everyone! I first want to start off by saying this is my first time posting on this forum and recently purchased my first Subaru. I bought a 2006 wrx In August '15 from a used car dealership. I know..I know.. a risky move. The wrx has 112,000 miles, very clean, and had a long maintenance history on carfax. I'm a Chrysler Technician and have good mechanical knowledge. I inspected the car very thoroughly, Undercarriage has little to no rust, engine bay spotless, interior 9/10, body 9/10. Had minimal mods, although put up a red flag right away. HKS vta bov, HKS Hi-power catback exhaust, and a short ram air intake. Test drove vehicle for about 30 min, no abnormal noises and drove very well. The only thing that stood out to me was that I was expecting it to have better acceleration. Before this I dailyed my Miata for the last 3 years, and this wrx felt about the same, but with more torque. So, long story short I bought it and it has been a PITA since. What I've done since buying it after realizing somethings wrong: Stock temp NGK Iridium sparkplugs gapped to .028", Fuel line feed side damper (Had knocking sound by driver side door sill area a day after buying it), Mishimoto intercooler hose kit, cleaned throttle body and new gasket, intercooler bpv gasket, intercooler y-pipe gaskets, a Perrin turbo inlet hose, replaced hks bov with a stock BPV. I also performed
    a compression and leak down test on the engine. Compression test results were 135 psi (dry) on all cylinders. Leak down test results were Cyl.#1- 7% Cyl.#2- 7%Cyl.#3- 13% Cyl. #4- 7%.
    All cylinders were leaking by crankcase blow-by. Ran vehicle up to operating temp and took oil cap off. Has a good amount of blow-by, but no smoke and just smells like oil not exhaust gases. Flipped oil cap up-side down and placed cap on oil filling hole, showed that the blow-by has a equal vacuum sucking in. I believe the engine is in decent condition and not part of my underboost issue. When replacing the turbo inlet (PITA install) I was just able to get my finger tips on the compressor impeller. The impeller had a <1/8" wobble side to side , being my first boosted car I instantly thought it had a bad turbo. After researching on the subie forums i found that it's normal due to when the engine is running the oil takes up this clearance. I couldn't get a great grip on the shaft, but from what I can tell it doesn't have any in-out shaft play. Also no whining/screaming/grinding under accel/boost. So, from there no difference has been made. After more hours of forum browsing I started looking into the waste gate/actuator. Actuator holds vacuum, moves with pressure applied, and is connected properly. Tested/cleaned boost solenoid- working correctly. Checked all vacuum lines, checked for restrictor pill and proper line routing to wategate solenoid and actuator- all good. I currently have no data-logging software at this time. I hooked up a basic scan tool from work and did some live data runs. Everything looked good except the Maf was maxing out at 120 g/sec at 5k + rpm in any gear. My understanding is it is suppose to be mid to upper 200's?? Cleaned the maf a couple time with maf cleaner, reset ecu with no difference. My next step was to get a cheap boost gauge, hooked it up and did some pulls..... 5psi-7psi in 3rd gear. 5 ish psi is 1st and 2nd. Stock is 11.5 psi? So, after more forum searching I started looking into the wastgate actuator since i'm running right around waste gate pressure, 7psi. Ended up pulling off the vacuum line off actuator and took it for a careful ride. Same result 7 psi max in 3rd gear, above 4.5k rpm. . Next step I did was remove actuator rod and wire strap the wastegate shut, and take it for another drive. Same result, so now i'm stumped. Next i'm going to do a boost leak test even though all the hoses are new. Maybe the intercooler has a hole or end-tanks leaking (had intercooler off and inspected for damage nothing found, also straightened all bent fins on intercooler). Boost gauge goes right up to 5-7 psi rapidly every time and holds steady. Vacuum is at -22 idle, -24 decel. Goes right to zero jabbing throttle in neutral. 0-60 mph takes about 9 seconds. So my ideas are a large boost leak (new hoses, steady boost and no squealing leads to no boost leak?), large exhaust leak or clogged cat (exhaust is very quiet even with hks hi-power muffler w/no baffle.) Bad turbo (no abnormal noises under boost), Engine issue (even though unplugging hose off actuator by-passes all electrical limitations like boost solenoid, ecu pulling timing). I've done a hand full of ecu resets with no improvements. I'm running 93 octane. I'd appreciate any help or tips in trying to solve this issue, Thanks!!
    Last edited by Sayre1525; 09-13-2015 at 05:01 PM.

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