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Banned
2004 Subaru Outback H6.30 35 anniversary edition
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249 Posts
Discussion Starter · #1 · (Edited)
Hi,

I have 2004 H6 3.0 35 anniversary edition that stalls on stops or when in reverse. It seems like it has problem downshifting (I can avoid stalling by manually shifting to 3, 2, 1 at stop signs). It also stalls if I put the car in neutral when stopping.

Shifting is rough.

Once I had this symptom I have flushed ATF and replaced air filter (just in case). Same thing.

You advice is greatly appreciated!

PS: the only other thing that is wrong with the car - perennial CEL due to low efficiency cat. converter (P0420 I believe). The problem with stalling developed suddenly. Stood in the parking lot for 8 hours. Drove off (reverse first). Stalled on second stop sign and never failed to fail since then.

PPS: To check that P0420 is not masking any new codes disconnected the battery (to reset CEL). Drove for 10 minutes. No CEL. (P0420 usually takes about 1 hour of driving to appear). From this I conclude there is no new codes thrown.
 

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On the Super Mod Squad
2002 3.0 VDC Wag + 2018 2.5 Leg Ltd
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26,945 Posts
p0420 is unrelated,...typical nag problem here and with other cars.

miles on this? any other dash lights.
 

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Banned
2004 Subaru Outback H6.30 35 anniversary edition
Joined
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249 Posts
Discussion Starter · #3 ·
I was just trying to include all info. Other than that CEL no other lights. When car stalls the usual - "At oil temperature" "Battery" and sometimes "BRAKES" comes on. 203K miles. Has been running like champ so before this started to happen (two days ago).


p0420 is unrelated,...typical nag problem here and with other cars.

miles on this? any other dash lights.
 

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Meh.
I has wagons.
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12,356 Posts
Battery or alternator perhaps.
 

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Premium Member
(formerly) 03 H6 OBW , (presently) 06 WRX Sportwagon & 2021 Honda CR-V
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18,391 Posts
does it feel odd before it stalls? wonder if the the torqu converter is not releasing???

if you were to (safely) shift to neutral before stopping, does it stall immediately, only when you hit the brakes, or not at all?
 

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Banned
2004 Subaru Outback H6.30 35 anniversary edition
Joined
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249 Posts
Discussion Starter · #6 ·
If I just switch to neutral nothing happens (though I should say I my have not had enough distance just to coast to see what happens if I just slow down to a stop that way). Stalls as I press the brakes.
 

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Premium Member
(formerly) 03 H6 OBW , (presently) 06 WRX Sportwagon & 2021 Honda CR-V
Joined
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18,391 Posts
sometimes a bad brake booster will cause stumbling/stalling.

If you are idling and step on the brakes - does the engine stall or stumble? any odd sounds form the dash area?



 

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Registered
OBW H6 VDC, Tribeca, XT6
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12,385 Posts
When stopped two things need to happen:

1. the engine needs air because the throttle is closed. Subaru controls this with idle control valves, though I've never heard of one failing on an H6 so I don't even know where they are.

Normally you clean them first to see if that resolves it, install a used one (because they're easy and rarely fail so they're cheap), or install a new one.

2. The torque converter is what allows the engine to keep running when the transmission is not. I haven't seen it either but I woudl presume there's a TC lock up clutch failure mode that prevent the torque converter from unlocking and stalls the engine.

Check your transmission pan and make sure it isn't dented as the uptake and wiring clearances between the pan and transmission are miniscule and the wiring/solenoids are easily damaged with any dent.

Some H6's had TPS issues - and they wouldnt' always throw a code. I think it was just earlier ones like 01-02 but if the sensor/intake/engine were ever swapped it could have an older one and maybe my memory is foggy and it includes new ones sometimes?
 

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Banned
2004 Subaru Outback H6.30 35 anniversary edition
Joined
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249 Posts
Discussion Starter · #9 ·
OK, just got car from stealership. The car has been there since 08/28. My pocket is $1K lighter.

They basically have no idea! This is what they did:

- replaced gasked throttle chamber (no effect)
- replaced air control valve gasket (no effect)
- flushed ATF (no effect)
- replaced transmission sensor harness (no effect)

Then they - "plugged in new TCM (transmission control module) - engine won't stall. Plugged back old TCM, no problems. Test drove for 28 miles - no problems" Flakey contact on TCM?

Well, I did get to drive new Forester, so something to show for $1K. ($600 labor, $400 parts)

additional point: they discovered that if car is set into FWD, no stalling issues were observed.
 
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