I got myself into a completely stock manual 2009 LGT with low mileage (73000) over the summer. Trying to work out the kinks and getting it caught up on maintenance (plugs, timing belt etc), popped a lean P0171 a couple months back. At the time, my little OBD scanner was returning high numbers on both short and long-term fuel trim (well above 10%).
Replaced the MAF, as 2 smoke tests from different shops came back with nothing. That *did* take care of the CEL, and now the car’s *short term* trim is A-OK (hovers between 0-5%).
Still having awful LTFT - anywhere from 15-25%. Symptoms:
- poor gas mileage
- severe reduction in power (everything seems “wheezy” or “gaspy” if that makes sense)
- The trim *does* get back into normal range when not at engine idle.
I did end up taking it in to Subaru to take a look. They told me that the issue is a problem with a solenoid on one of the tumble generator valves. I balked initially due to the price quoted, but also because they weren’t super honest about a spark plug issue the car was having at the time.
Still had a limited extended warranty on the car at the time, but the company refused to cover the TGV replacement “because it’s an electronic part [the solenoid] that is malfunctioning.” (warranty covered the manifold itself but apparently not connected electronic parts, even though Subaru’s recommendation was replacement of *both* TGVs)
Really looking to vent and see if anyone has any advice. Thanks to y’all I’ve seen that it’s *probably* still a leak somehwere? And if not, that it could potentially be the PCV valve or one of the O2 sensors? Or Subaru was being totally legit and it truly is the tumble valves. I’m just hesitant to jump straight to their fairly pricey recommendation.