fevafeav Posted August 23, 2013 Share Posted August 23, 2013 ok......... so. i recently bought a 1994 twin turbo gt legacy with a stuffed primary turbo. my intention was to buy the car, fix it and then sell it on. i knew they arent the easiest cars engine wise compared to some but thought i was quite capable of fixing it as i have worked on cars for 8 years and have completed level 3 automotive engineering (still have 2 thirds to go to become a qualifed mechanic, have been slack on paperwork lol) anyway... i proceeded to replace the primary turbo. upon test driving it the CEL came on and i did a manual code check to find the dredded fault code 66 (sigh) i then did some fault finding over the next week in my spare time checking everything i could think of - maf sensor cleaned, performed diagnostic check by plugging in the green plugs under the dash and listening to the solenoids working with a stethoscope, the vacuum canister evacuating, actuators working etc etc... i had heard that the black solenoid boxs (BboD) can give trouble so swapped it with another one with no joy. cleaned and checked all vacuum lines including the one at the front that runs along under the bumper, checked differential pressure sensor, and checked for boost/air leaks. in the end found that BOTH the bypass valves were faulty so replaced them and then BOOM- primary turbo boosting with no fault code!! a while later i went out of town and on the motorway gave it a bit of a thrashing to make sure it was all good but...... found that when the transition between primary and secondry turbo occured the boost pressure dropped from around 13psi to 6-7 psi!!??!! i feel at this stage that it may also have a faulty secondry turbo....???? so for the mean time i dont operate the engine in that rev range untill i can be botherd checking it..... anyway there are a couple of other things..... the other day i noticed under boost on primary turbo the engine was missing/fuel cutting but with no check engine light? i have not yet checked the sparkplugs or coil packs as i have not had time but i dont see why it would fuel cut like it did if they were the issue.... also it seems to use a sh**load of gas compared to my rb20det nissan laurel. and i mean a s**tload. almost 3 times as much. i know that the cat has been cut out so no blockages and i havent checked o2 sensors yet as dont have the equipment at home and dont have time to do it at work. i have changed the fuel filter as the old one was old and sh**ty looking. but im wondering if maybe these faults could be related? could anyone please shed some light on this for me as im getting really sick of this car and i dont have the time to be spending hours checking things. this is the first twin turbo subaru i have ever had anything to do with engine wise and thought maybe somebody may have had similar problems that could help. sorry about the long as post lol. took me like half an hour to type up. please help:spin: Link to comment Share on other sites More sharing options...
johnegg Posted August 23, 2013 Share Posted August 23, 2013 hope this helps. ok......... so. i recently bought a 1994 twin turbo gt legacy with a stuffed primary turbo. my intention was to buy the car, fix it and then sell it on. i knew they arent the easiest cars engine wise compared to some but thought i was quite capable of fixing it as i have worked on cars for 8 years and have completed level 3 automotive engineering (still have 2 thirds to go to become a qualifed mechanic, have been slack on paperwork lol) anyway... i proceeded to replace the primary turbo. upon test driving it the CEL came on and i did a manual code check to find the dredded fault code 66 (sigh) i then did some fault finding over the next week in my spare time checking everything i could think of - maf sensor cleaned, performed diagnostic check by plugging in the green plugs under the dash and listening to the solenoids working with a stethoscope, the vacuum canister evacuating, actuators working etc etc... i had heard that the black solenoid boxs (BboD) can give trouble so swapped it with another one with no joy. cleaned and checked all vacuum lines including the one at the front that runs along under the bumper, checked differential pressure sensor, and checked for boost/air leaks. in the end found that BOTH the bypass valves were faulty so replaced them and then BOOM- primary turbo boosting with no fault code!! a while later i went out of town and on the motorway gave it a bit of a thrashing to make sure it was all good but...... found that when the transition between primary and secondry turbo occured the boost pressure dropped from around 13psi to 6-7 psi!!??! ! i feel at this stage that it may also have a faulty secondry turbo....???? so for the mean time i dont operate the engine in that rev range untill i can be botherd checking it..... anyway there are a couple of other things..... the other day i noticed under boost on primary turbo the engine was missing/fuel cutting but with no check engine light? i have not yet checked the sparkplugs or coil packs as i have not had time but i dont see why it would fuel cut like it did if they were the issue.... also it seems to use a sh**load of gas compared to my rb20det nissan laurel. and i mean a s**tload. almost 3 times as much. i know that the cat has been cut out so no blockages and i havent checked o2 sensors yet as dont have the equipment at home and dont have time to do it at work. i have changed the fuel filter as the old one was old and sh**ty looking. but im wondering if maybe these faults could be related? could anyone please shed some light on this for me as im getting really sick of this car and i dont have the time to be spending hours checking things. this is the first twin turbo subaru i have ever had anything to do with engine wise and thought maybe somebody may have had similar problems that could help. sorry about the long as post lol. took me like half an hour to type up. please help:spin: Link to comment Share on other sites More sharing options...
monkeyposeur Posted August 23, 2013 Share Posted August 23, 2013 Most of us in this forum don't have a lot of knowledge about the twin turbo set up as they are rare as a purple unicorn in the states. I'd get on sli.net for more info as there are a few tt owners over there. http://sl-i.net/FORUM/index.php?sid=4ecb1bed7496b67a4d57183f2aff027e Link to comment Share on other sites More sharing options...
Zues Marine Posted August 23, 2013 Share Posted August 23, 2013 pffff sl-i... check out uklegacy.com, they know 150000x more about the 20tt and jdm stuff than anyone on sl-i or lgt Link to comment Share on other sites More sharing options...
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