High Long Term Fuel Trim, Advice?

[nolenium]

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.

[whitetiger]

what is your 02 sensor reading? you STFT seems to have leveled out so its probably a very small vac leak, or you could have a clogged injector too where the sytem was able to compensate. if you had a larger leak, the STFT would be pegged as well.

[nolenium]

what is your 02 sensor reading? you STFT seems to have leveled out so its probably a very small vac leak, or you could have a clogged injector too where the sytem was able to compensate. if you had a larger leak, the STFT would be pegged as well.

 

Sorry for my ignorance - my scanner is one of those universal apps so I see options for multiple banks and sensor #s for O2.

 

On our Legacies is it just "Bank 1 Sensor 1/2"? Or do I need to be looking at any other banks/sensor #s?

[nolenium]

Not too sure which reading I should be looking at - looks like my OBD scanner app has a lot of different stuff for both O2 sensors.

 

At this point I'm thinking about heading to a 3rd shop to do another smoke test, or at least maybe a confirmation that Subaru isn't pulling my leg and there really *is* some kind of issue with a solenoid on the tumble generator valve.

[JoeInOregon]

My knowledge is pretty limited with these cars....is there a reputable performance Subaru shop in town ? Or Subaru only shop, I'm really fortunate as I have two shops I trust.

 

You should do find a shop you trust if you don't trust the dealership.

 

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[JoeInOregon]

If it really is a problem with TGV, a good performance shop will be able to diagnose that and replace for cheaper than the dealer, if could find a shop that would do it, would be perfect time to get TGV deletes and a tune

 

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