Akita Posted June 8, 2012 Share Posted June 8, 2012 Hi everyone. I have a problem that has been giving me trouble for years. I have a 1997 Legacy 2.5GT manual trans. I bought the car with 75k miles. It now has 125k. This is the problem: from 0-3k RPM, the car more often than not bucks/hesitates BADLY. Other times it rockets off the line especially if I am anticipating bucking/hesitation. Over 3k RPM it drives just fine. It will do this basically whenever it feels like (in the morning on startup or after driving around all day) The car has never thrown a CEL (CEL light is working). I have replaced the spark plugs, spark plug wires, EGR, front O2 sensor, and performed all regular maintenance. When I replaced the front O2 sensor, the car drove well for about a week then slowly degraded over the next three weeks until I was back at where I was before the O2 sensor replacement. I'm planning on replacing the PCV valve, front O2 sensor (again), fuel filter, and fuel pressure regulator this weekend. I'll let you know if that fixes it. In the meantime, please help! Link to comment Share on other sites More sharing options...
Akita Posted June 11, 2012 Author Share Posted June 11, 2012 Update: the new O2 sensor, fuel filter, and fuel pressure regulator did not fix the problem. Still no CEL. Any thoughts? Which engine systems could fail and not trigger a CEL? Link to comment Share on other sites More sharing options...
Willson556 Posted June 19, 2012 Share Posted June 19, 2012 I had a similar issue in my '05 LGT. It turned out to be a clogged catalytic converter in the down pipe. You could try checking that. Link to comment Share on other sites More sharing options...
Akita Posted June 30, 2012 Author Share Posted June 30, 2012 It could be the cat. Everything I've read says symptoms of a plugged cat are steady loss of high end power over time. I have the opposite problem in that 1-3,000 RPM sucks and after 3k the thing takes off. I'm wondering if it could be the TPS. Could a TPS be out of whack and not throw a CEL? Link to comment Share on other sites More sharing options...
rjh2pd Posted July 26, 2012 Share Posted July 26, 2012 Hi, I'm having this same problem. I have an 03 legacy AT. It really only happens when starting from a stop. Have you figured it out? any help would be greatly appreciated. EDIT: i just read this, might help ... http://www.ultimatesubaru.org/forum/showthread.php?t=42046 Link to comment Share on other sites More sharing options...
Akita Posted August 15, 2012 Author Share Posted August 15, 2012 Hi everyone. I wanted to update you on the problem. It was the knock sensor!! Subaru of North Reading, MA noticed a bulletin (not a recall) on '99 Legacy sedans that described my problem. Replaced the part last night and it is like driving a new car! Apparently the knock sensor is overly sensitive and will detect a non-existent engine knock and thus retard timing to compensate for the knock. The sensor is functioning as it should so no CEL. They are just too sensitive. Part was about $110. Make sure you ask if there is a superseded part number for your knock sensor. That will likely indicate Subaru has replaced the OEM part with one that is less sensitive. Fair warning: the part is pain to replace on your own!! Good luck! Link to comment Share on other sites More sharing options...
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