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Discussion Starter · #1 ·
Hello all, back again for the folks that know more about subies than I do.

In the last few months my '13 Forester XL has thrown me for a loop. It began in the winter throwing p0420, figuring my O2 sensor was the suspect I changed it out with a OE Denso and everything seemed fine. A week later it began lunging and pulsing terribly while under normal driving conditions(for me is mostly mountain 45/55 and some highway 60/70mph). Now it runs terribly, cleaned my MAF every oil change, makes no difference. Fuel consumption has gotten ridiculous I only average 13ish mpg, car shuts off at stop lights/signs, but I've noticed pumping brakes can help keep it stuttering long enough to tap accelerator a few times and keep it running. When I start it up in the mornings 80% of the time of I leave it to "warm up" in a couple minutes when I come back out it's shut off, each trying as of you simply turned the key off. I'm speculating but it seems to have a serious fuel/air mixture issue.

I've thought that possibly sure to the original engine burning so much oil my cat is stopped up ( dealer swapped short block about 50k miles ago). I tried getting the dealer to replace cat and both OF sensors due to pull consumption but they tell me it's not covered. I'm at a loss here, has anyone ever dealt with this or something similar? Thank y'all for your time in advanced.

Hunter
 

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2017 Forester 2.5i CVT
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Some suggestions you can try. Have you inspected your belts? The new EPDM belts don't crack, but the belt gets thinner and the grooves worn and wider until it could be slipping but without squealing much. This can cause stalling as your alternator flow is weakened. I changed mine at 94000 miles and was shocked when my headlights got brighter and my gas mileage went up. But mine is a single Serpentine, I think your car has two...
Sometimes partly clogged CATS can be freed up by a high percentage PEA fuel system cleaner, I prefer CRC Guaranteed to Pass as costing half what Cataclean does, but try either one put in right before filling a near empty tank, run down to 1/8 tank next.
Lastly get a decent moderately priced scanner in the $50 to $100 range and see what it tells you, you may for example detect misfiring not severe enough to trigger a check engine light but compromising performance. My Ancel 410 is cheap, but it tells me a whole lot of usefull things. Good luck and let us know.
 

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Discussion Starter · #3 ·
Some suggestions you can try. Have you inspected your belts? The new EPDM belts don't crack, but the belt gets thinner and the grooves worn and wider until it could be slipping but without squealing much. This can cause stalling as your alternator flow is weakened. I changed mine at 94000 miles and was shocked when my headlights got brighter and my gas mileage went up. But mine is a single Serpentine, I think your car has two...
Sometimes partly clogged CATS can be freed up by a high percentage PEA fuel system cleaner, I prefer CRC Guaranteed to Pass as costing half what Cataclean does, but try either one put in right before filling a near empty tank, run down to 1/8 tank next.
Lastly get a decent moderately priced scanner in the $50 to $100 range and see what it tells you, you may for example detect misfiring not severe enough to trigger a check engine light but compromising performance. My Ancel 410 is cheap, but it tells me a whole lot of usefull things. Good luck and let us know.

Sorry its taken so long to get back in here. I have since this last post, replaced Serp belt and tensioner, MAF ( with OE denso), air filter, and cleaned MAP all in vain. I borrowed a friends Zurich scanner and i have several sensors that are all over the place. My fuel trims are out of control with STFT running a pretty steady lean ~ -28 and LTFT running either an exact copy of STFT or ~ -0. MAP is all over the place but mean average of 8, MAF appears to be somewhat normal( due probably to being a brand new sensor) To put it bluntly this thing runs like poop and im passed the point of frustration with it. Last week taking my kids to school trying to pull off from a stop sign( after putting foot into the accelerator) it just shut off and I had to shift to nuetral, restart, drop in drive and go ASAFP. I', reaching witts end with this thing.
 

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2001 Forester S, 4EAT
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Vacuum leak is something to look at as you say pumping brake pedal seems to help.
 

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Discussion Starter · #5 ·
I had suspected that initially hooked it up to smoke machine at work and didn't find anything also shot about half a can of chlorinated brake cleaner around different suspected spots and never got any rise in RPM. That's what is driving me nuts about this thing, nothing makes sense 🤬
 
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