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Old 03-16-2021, 08:19 AM   #26
Elbert Bass
Scooby Specialist
 
Member#: 283429
Join Date: May 2011
Chapter/Region: South East
Location: Down yonder.
Vehicle:
2016 Fuji Sunfire 03
Silver

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Quote:
Originally Posted by jimmy12345678 View Post
Okay, still having issues with my Subie, which I'll explain below.

It's still making the rattling noise at high RPM's, but now on a recent road trip the car would barely climb a hill, I had to pick up speed and play with the gears to keep up my speed enough to climb any steep grade, had to use my flashers a couple times because the car just wouldn't keep up with traffic. Did manage to make it home. It set a MIL approximately 45 miles from home after poor performance and fuel economy for the entire trip (around 19 mpg, whereas last summer we averaged around 29-30 under similar driving conditions). I also noticed that the car would "surge" when I'd manually shift into 4th gear at times and it still wanted to rev high and had no power in 2nd gear, and next to no power in 3rd.

The codes stored in the PCM were a current P1153 O2 sensor circuit/range performance B1S1, a pending P1153 and a P0171 system too lean code. Just got back home this evening so haven't had time to diagnose anything yet, but my "gut" is telling me it's a failing fuel pump based on the driveability issues.

I'm still at a loss. Will be doing some diag work tomorrow but what do you guys think of this new development with this issue?
So now you have a lean code? I don't see mention of that before - is this something new? So it is possible it is spark knock from a very lean condition. I had mentioned checking fuel trims before. Your lack of response on that led me to believe they were acceptable.
Did you get freeze frame data from when the P0171 set? are both long and short term trims high positive numbers?

Yes, fuel pump is a possibility. You will need to check fuel pressure to verify. It may not be evident at idle and only show low pressure during the rattle under load. In fact, I have seen water in fuel filters cause that. Fuel flows fine under normal load but as soon as you increase demand for fuel flow (accel up hill or heavy load) the water in the filter media will only let's so much fuel through and pressure drops. The amount of water won't be much, could be accumulation of moisture over the years from condensation in the tank. It doesn't take much to soak the filter and block fuel flow.
That is the drawback with a single ended fuel supply and a "lifetime" filter in the the tank on the pump assembly.
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Last edited by Elbert Bass; 03-16-2021 at 11:00 AM. Reason: adding info
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