Legacy25GT2005 Posted May 19, 2011 Share Posted May 19, 2011 Hoping someone can help me out with this one... 2005 Legacy Sedan 2.5GT/Turbo. About 100,000 miles total; engine was rebuilt (rings, bearings, etc) and new turbo installed about 12,000 miles ago after turbo oil starvation. Starting about a month ago: Accelerate away from full stop, acts fairly normal. Reach 20-30 MPH, then try to accelerate further by giving more gas. Nothing...happens... Engine RPM lags, mph holds steady or drops back (if going uphill, for example). Push gas pedal to floor; nothing happens. Pump gas pedal; no or little response. Eventually - 5, 10, 20 seconds later - turbo kicks in, engine rapidly revs up, mph increases dramatically. So long as I keep engine speed up and turbo engaged, all is well. Reach a traffic stop or red light and the whole process starts all over again. My mechanic checked Lord knows how many things: exhaust system good, fuel pump good, turbo good, air flow good, spark good, compression good, and so on. What are we missing? Link to comment Share on other sites More sharing options...
dwolson2 Posted May 19, 2011 Share Posted May 19, 2011 tuned? Factory? Logs? Link to comment Share on other sites More sharing options...
Legacy25GT2005 Posted May 19, 2011 Author Share Posted May 19, 2011 tuned? Factory? Logs? Stock with no modifications other than engine rebuild as previously noted. Logs? What are logs? Can I get a vote on possible bad throttle position sensor? Would that account for the symptoms? Link to comment Share on other sites More sharing options...
FocuS Posted May 19, 2011 Share Posted May 19, 2011 Logs=Data logging of ECU conditions...easy to do with a laptop and correct cabling... Link to comment Share on other sites More sharing options...
dwolson2 Posted May 19, 2011 Share Posted May 19, 2011 Stock with no modifications other than engine rebuild as previously noted. Logs? What are logs? Can I get a vote on possible bad throttle position sensor? Would that account for the symptoms? I *think* all subies can log with a regular vag com cable(OBD2 ebay cable for 20$) I think 07+ must use the tactrix for flashing. If you use a program called Romraider, which is free, you can "log" what your engine is doing, so we can actualluy see if a sensor is bad, misfire, etc.... It would tell us a lot more, or may even tell us exactly whats wrong. With out guessing Link to comment Share on other sites More sharing options...
rapture Posted May 19, 2011 Share Posted May 19, 2011 go get a tune!! awd dyno tune and buy a cobb access port. research both terms^ Link to comment Share on other sites More sharing options...
dwolson2 Posted May 19, 2011 Share Posted May 19, 2011 before tuning, he needs to make sure there is nothing mechanical wrong with his car, or he could be compounding his problems. After that, FTW Stage 2! Link to comment Share on other sites More sharing options...
dwolson2 Posted May 19, 2011 Share Posted May 19, 2011 Actually, I just read, you have a 05, so the Vagcom cable would do both logging and tuning(if you went open source or used infamous1's etune...search) Link to comment Share on other sites More sharing options...
Legacy25GT2005 Posted June 9, 2011 Author Share Posted June 9, 2011 I *think* all subies can log with a regular vag com cable(OBD2 ebay cable for 20$) I think 07+ must use the tactrix for flashing. If you use a program called Romraider, which is free, you can "log" what your engine is doing, so we can actualluy see if a sensor is bad, misfire, etc.... It would tell us a lot more, or may even tell us exactly whats wrong. With out guessing Actually, I just read, you have a 05, so the Vagcom cable would do both logging and tuning(if you went open source or used infamous1's etune...search) Would someone mind pointing me to the correct cable on eBay or other vendor, please? Link to comment Share on other sites More sharing options...
cypher0117 Posted June 9, 2011 Share Posted June 9, 2011 contact m sprank. He has a vagcom cable, and all software needed delivered for $30 Link to comment Share on other sites More sharing options...
MasAyinde Posted June 9, 2011 Share Posted June 9, 2011 This works perfectly for me: [ame=http://www.amazon.com/gp/product/B002WIN8VQ]Amazon.com: OBD2 OBD II Diagnostic USB Cable KKL409.1 VAG-COM 409: Electronics[/ame] Link to comment Share on other sites More sharing options...
TheBoostNazi Posted June 9, 2011 Share Posted June 9, 2011 any check engine lights? my first thought was a boost leak when the psi rises.. assuming all exhaust is normal and there aren't any leaks, it almost sounds like a wastegate malfunction of some sort....you say the turbo kicks in, it's obviously spooling but the power might not be generated into the throttle body. just a thought. Link to comment Share on other sites More sharing options...
Legacy25GT2005 Posted June 9, 2011 Author Share Posted June 9, 2011 any check engine lights? my first thought was a boost leak when the psi rises.. assuming all exhaust is normal and there aren't any leaks, it almost sounds like a wastegate malfunction of some sort....you say the turbo kicks in, it's obviously spooling but the power might not be generated into the throttle body. just a thought. No lights, no codes. This has all gotten very complex over the past several weeks and I can only get part of the story out just now so please bear with me. 1) some oil blowing through turbo/throttle body gasket, raw oil getting into throttle body. Replaced gasket and cleaned out oil; mechanic thought that would solve the problem; didn't. 2) insides of pre-cat (?) were rotted and clogged up. Replaced; mechanic thought that would solve the problem; didn't. 3) bad sensor (not sure which one) connector on wire harness; replaced entire harness; thought this might finally be it; wasn't 4) replaced transmission control computer with a used one just for kicks; didn't help 5) considered replacing ECU with a used one, but ran into problems with key codes not matching and so engine start locked out. 6) and on and on. I will try to post more later. As it stands right now, after an ECU reset, car runs great for about 20 minutes then suddenly starts acting up again. Reset the ECU and it's good for another 20 minutes. In my small mind, I assume this might mean that there is a bad sensor signal which is not getting to the ECU causing it to mis-calculate proper engine conditions after a 20 minute "learning period". Or possibly a bad ECU? Any thoughts on that? Right now I am thinking I would like to grab logs during the 20 minutes that engine runs great and again when it is running like crap and maybe someone here will be able to spot something. Link to comment Share on other sites More sharing options...
TheBoostNazi Posted June 9, 2011 Share Posted June 9, 2011 front o2 sensor.... when the car warms or learns, the engine starts rich then leans the fuel trim out once up to operating temp, and may not be doing it properly, faulty readings causing eradic performance. not all bad o2 sensors throw a code, some can be acting up well before a code is thrown Link to comment Share on other sites More sharing options...
Legacy25GT2005 Posted June 9, 2011 Author Share Posted June 9, 2011 just got off the phone with the mechanic...apparently the front o2 sensor was melted by engine overheating. they checked wire and the connector that plugs into the back of the engine (brown, circular ??) which i've heard that subaru has had problems with. about to airllift my car to afghanistan with me and blow it up @ the range. Link to comment Share on other sites More sharing options...
TheBoostNazi Posted June 9, 2011 Share Posted June 9, 2011 that's an easy fix. could have been worse! consider yourself lucky Link to comment Share on other sites More sharing options...
Legacy25GT2005 Posted June 9, 2011 Author Share Posted June 9, 2011 that's an easy fix. could have been worse! consider yourself lucky I am afraid you misunderstood my son's post (that last one was by him). The front o2 sensor was replaced early on in this process after it melted - see this related thread for more details on that mess http://legacygt.com/forums/showthread.php/another-blown-engine-2005-legacy-2-5gt-turbo-162696.html As it stands, my mechanic (who I really trust; all they do is Subarus) has been tearing his hair out trying to find the problem. Link to comment Share on other sites More sharing options...
TheBoostNazi Posted June 9, 2011 Share Posted June 9, 2011 interesting... well logging will help us.... Link to comment Share on other sites More sharing options...
Legacy25GT2005 Posted June 9, 2011 Author Share Posted June 9, 2011 interesting... well logging will help us.... I should be able to post some logs the middle part of next week. Thanks for your help thus far. Link to comment Share on other sites More sharing options...
1454 Posted June 9, 2011 Share Posted June 9, 2011 No lights, no codes. This has all gotten very complex over the past several weeks and I can only get part of the story out just now so please bear with me. 1) some oil blowing through turbo/throttle body gasket, raw oil getting into throttle body. Replaced gasket and cleaned out oil; mechanic thought that would solve the problem; didn't. 2) insides of pre-cat (?) were rotted and clogged up. Replaced; mechanic thought that would solve the problem; didn't. 3) bad sensor (not sure which one) connector on wire harness; replaced entire harness; thought this might finally be it; wasn't 4) replaced transmission control computer with a used one just for kicks; didn't help 5) considered replacing ECU with a used one, but ran into problems with key codes not matching and so engine start locked out. 6) and on and on. I will try to post more later. As it stands right now, after an ECU reset, car runs great for about 20 minutes then suddenly starts acting up again. Reset the ECU and it's good for another 20 minutes. In my small mind, I assume this might mean that there is a bad sensor signal which is not getting to the ECU causing it to mis-calculate proper engine conditions after a 20 minute "learning period". Or possibly a bad ECU? Any thoughts on that? Right now I am thinking I would like to grab logs during the 20 minutes that engine runs great and again when it is running like crap and maybe someone here will be able to spot something. If its not the o2, see if you can find someone else with a lgt and swap the mass air sensor. Had the exact samething on a supercharged frontier we had at the dealer I work for. Link to comment Share on other sites More sharing options...
Legacy25GT2005 Posted June 9, 2011 Author Share Posted June 9, 2011 If its not the o2, see if you can find someone else with a lgt and swap the mass air sensor. Had the exact samething on a supercharged frontier we had at the dealer I work for. I am 99% certain he already swapped the mass air sensor as well (my son would know for certain). Link to comment Share on other sites More sharing options...
1454 Posted June 9, 2011 Share Posted June 9, 2011 Then I would start looking at wiring. Like others have said, you need some good logs, I would say a solid 20-30 min drive cycle to see what the voltages are showing on each individual sensor. Then you can try to pin something down from there. I know that engine swaps, as easy as they are in these cars, can sometimes result in pinching a wire some where, which then causes problems. Also, and I doubt this is it, but check the ground to the motor. That's shouldn't be a rpm based issue, but it obviously doesn't hurt. Without "seeing" what is going on, it's hard to diagnose. Well, actually, it's hard to diagnose without have the car physically in front of you. Link to comment Share on other sites More sharing options...
Legacy25GT2005 Posted June 10, 2011 Author Share Posted June 10, 2011 Then I would start looking at wiring. My guy feels the same; he says it must be an intermittent short/ground because there aren't any options left. The engine and all components are mechanically sound, sensors have been replaced with new or swapped with known good parts, an entire wire harness swapped out (sorry, not sure which one exactly), and so on. About the only thing which hasn't been swapped is the ECU itself. I do have a bit more detail: Not certain that simply resetting the ECU is not enough to (temporarily) restore normal operation. He thinks now it is more likely the process of disconnecting/reconnecting various systems that may be responsible for these brief periods of normalcy. We picked up the car last night and my son said it ran great for most of the 5 mile/20 minute drive home but began acting up as we neared the end of the drive. I should be able to post logs in a few days. Link to comment Share on other sites More sharing options...
06_legacygt Posted June 10, 2011 Share Posted June 10, 2011 i know this sounds silly but what about a failing EGT thats reading hot? before i swapped out for my catless up pipe and my pre-cat was failing the pipe would get hot and force the ECU to pull timing like crazy....i would make boost but the car wouldn't go anywhee no matter when i had the pedal at until the pipe cooled off. maybe the EGT is saying hotter then it really is.....just a thought 2006 Legacy GT 5EAT Perrin UP, SPT CAI, OBXR CBE, Catless DP, Perrin TMIC, Stage 2 AP tune Soon after BNR 16G, Infamous Tune Link to comment Share on other sites More sharing options...
Legacy25GT2005 Posted June 11, 2011 Author Share Posted June 11, 2011 EGT sensor would not be any more silly than all the other stuff that has been looked at... Okay, guys, so I received the VAG COM cable late yesterday. I installed RomRaider and the cable's port driver on an old WinXP notebook and should be ready to go. Now what? (a sticky would help!) Do I hookup, start the data logger and then go on a 5 minute drive around the block a few times, or what? What is the protocol for generating and posting a useful log to this site? Link to comment Share on other sites More sharing options...
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