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Discussion Starter #1
My 99 outback was driving fine, I took it to get the exhaust fixed because the pipe between the catalytic converter and the resonator fell off like 2 weeks before. It drove fine for a couple days then it started stalling randomly while at low speeds like at intersections.


It Idles great

Now if it is in neutral/park and I VERY slowly touch the gas pedal it will rev as high as you want.
If I blip the gas real quick it will stutter and come back to idle.
If I press gas hard it will stall.

If I put the car in drive, it will drive slowly idling as long as I don't touch the gas.
If I touch gas it will stutter REALLY bad and most of the time stall after a few seconds.
If I mash the gas hard and fast it can sometimes get past the stuttering and rev up and start driving but with bad hesitation and its shifting weird.

I've replaced the MAF and Throttle Position sensor, checked all electrical plugs, made sure there were no intake/vacuum leaks, verified PCV valve was good, IAC is clean, reset ECU by unplugging battery for 30 min., and fuel filter, spark plugs, and wires are about a year old.

Also, it's not throwing any codes besides the stupid P0440 evap code it has always had.


Anyone have any ideas?
 

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05 Xt beatin' to an inch of its life
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Is this when warm or cold? Does it exhibit the same symptoms when cold started and hot started? I’d be looking at upstream O2 sensor.
 

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My 99 outback was driving fine, I took it to get the exhaust fixed because the pipe between the catalytic converter and the resonator fell off like 2 weeks before. It drove fine for a couple days then it started stalling randomly while at low speeds like at intersections.


It Idles great

Now if it is in neutral/park and I VERY slowly touch the gas pedal it will rev as high as you want.
If I blip the gas real quick it will stutter and come back to idle.
If I press gas hard it will stall.

If I put the car in drive, it will drive slowly idling as long as I don't touch the gas.
If I touch gas it will stutter REALLY bad and most of the time stall after a few seconds.
If I mash the gas hard and fast it can sometimes get past the stuttering and rev up and start driving but with bad hesitation and its shifting weird.

I've replaced the MAF and Throttle Position sensor, checked all electrical plugs, made sure there were no intake/vacuum leaks, verified PCV valve was good, IAC is clean, reset ECU by unplugging battery for 30 min., and fuel filter, spark plugs, and wires are about a year old.

Also, it's not throwing any codes besides the stupid P0440 evap code it has always had.


Anyone have any ideas?
Check your fuel pressure. Mine did the same thing when the pump was half dead. Only gave me 20psi in all situations. Never changed.

Sent from my SM-G955U using Tapatalk
 

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2002 Pair: 3.0 VDC Wag & 2.5 Limited Sedan
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I wonder if whatever is causing the p0440 can not tolerate a quick stab at the go pedal.

but I also like the front o2 sensor, but I would hope it would cause a minor misfire or some other code(s).
 

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Discussion Starter #5
Is this when warm or cold? Does it exhibit the same symptoms when cold started and hot started? I’d be looking at upstream O2 sensor.
It doesn't matter if it's warm or cold

P0440 code always appears a couple days after an ECU reset, it has had that code for like 6 years and always drove ok.
 

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05 Xt beatin' to an inch of its life
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Pull the fuel pressure regulator and make sure it hasn’t completely failed internally. If you’ve had that code for years it’s diaphragm could be toast and now will not allow the engine to run normally. Also, its possible, if they did some welding, they could have spiked the ecu.
 

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Discussion Starter #8
Found the problem, the actual MAF connector was bad, ordered a used one off ebay and wired it in. Car runs now.

I have an issue now where the car will just randomly turn off, usually at stop, sometimes while driving it will lose power and come back, speed doesn't matter.
Turning the A/C on or turning Cruise control on makes it worse.
 

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05 Xt beatin' to an inch of its life
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Appreciate the report back on the diagnosis! That sounds as simple as a loose negative battery terminal connection. However, with what was done and what you've found- given the age, your ecu may be on its way out. It sounds like electrical problems may be unending... Further diagnoses over the internet will not be very fruitful in my guestimate. You'll need a decent multimeter and access to the factory diagrams and the technician's steps. Or, deep pockets and willing to pay someone who can troubleshoot. Good luck! Let us know what you come up with please.
 
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