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Old 01-18-2015, 08:29 AM   #1
888
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Member#: 269396
Join Date: Jan 2011
Location: Brookville Ohio
Vehicle:
2001 Legacy L wagon
Green

Default Cold idle stall and slight dash light flicker

Car is a 2001 Legacy 5MT with 127k on the 2,5 engine. What it does is stall when cold the first time or two I come to a stop. Just drops like a stone past where it should recover and idle. Once warming up, it drops a little past idle and recovers, once warm it idles like a kitten.

I've looked at some of the reference posts and it appears there are some recommendations for this problem, such as temp sensor, plugs and wires, fuel system cleaner, fuel filter. I've changed the fuel filter, added some Lucas fuel system cleaner, and ordered NGK plugs and Denso wires.

My only remaining question is how sensitive the Subaru fuel injection system is to vacuum? On a Bosch (early Volvo for example) FI system, it is extremely sensitive to vacuum and this could be a small crack in a vacuum line that closes when it gets warm. Any time I bought a Bosch FI car, I always replaced all the vacuum lines on general principles.

Second, I've noticed that the CEL pulses slightly at warm idle (750 rpm) when I use the turn signal or step on the brakes (brake lights on). CEL is on for 02 sensors for some reason I can't figure out, details elsewhere. Battery is 12.66V at rest, haven't checked the alt output yet but it should be decent if the battery is maintaining 12.66.

Maybe this is normal and I never would have noticed it if the CEL wasn't on, haha. I've seen something similar on my Cummins truck that has a sensitive ammeter. Anyone else notice this on their Subaru? Problem/no problem?

Thanks

Joe
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Old 01-18-2015, 10:18 AM   #2
g-heap
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So CEL is on for 02 sensor?
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Old 01-18-2015, 01:20 PM   #3
888
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Quote:
Originally Posted by g-heap View Post
So CEL is on for 02 sensor?
Yes, details here:

http://forums.nasioc.com/forums/show....php?t=2690983
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Old 01-18-2015, 04:56 PM   #4
g-heap
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Can't say why the CEL is still on about O2 sensors, since you replaced both. One time I had CEL on for O2 sensor, and replaced the front sensor (the "Air/Fuel Mixture Sensor") with NGK model and CEL went away. I understand Denso should work also, but maybe try swapping out with NGK?

Since the engine had been replaced merely with 100k on it, who knows what the issues were.

Only thing I can tell you is about slight flicker. When the turn signal is flickering, other lights on the dash may dim slightly in rhythm - nothing unusual.
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Old 01-18-2015, 07:46 PM   #5
888
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Quote:
Originally Posted by g-heap View Post
Can't say why the CEL is still on about O2 sensors, since you replaced both. One time I had CEL on for O2 sensor, and replaced the front sensor (the "Air/Fuel Mixture Sensor") with NGK model and CEL went away. I understand Denso should work also, but maybe try swapping out with NGK?

Since the engine had been replaced merely with 100k on it, who knows what the issues were.

Only thing I can tell you is about slight flicker. When the turn signal is flickering, other lights on the dash may dim slightly in rhythm - nothing unusual.
Thanks on the flicker question. I've heard and read all kinds of stuff on the 02 sensors. Denso is OEM and the main thing I read is that non OEM don't work. I didn't see NGK as being OEM but I could be wrong, it's kind of an expensive test. I want to read the codes again after some daily driving and go back through the wiring and see what happens.

I was hoping for some input on the vacuum question, I can just replace the lines, it's not expensive and fairly easy to do. I've seen stuff like this before out of Bosch CIS cars so I wanted to ask the questions.
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Old 01-18-2015, 08:17 PM   #6
g-heap
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Yeah, it's not such a bright idea. Those sensors aren't cheap, and you can't simply test and return them if they aren't the culprits.

Hope someone more knowledgeable will chime in.
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Old Yesterday, 11:06 AM   #7
888
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2001 Legacy L wagon
Green

Default

I've had more seat time on the car back and forth to work in the dark and I've noticed a few more things about this "flicker problem" mentioned previously.
I can see the pulse from the blinkers slightly dimming the dash lighting and exterior lights (when it's dark).
Same with the brake lights, I hit the brake pedal and I can see the dash and exterior lights dim slightly.
I pulled in the garage last night after a long trip and noticed that there was a slight unevenness in the intensity of lighting from DRL's on the back garage wall while the car was idling. Nothing other than maybe the HVAC fan on setting 1 was active, no other lights on.

The battery remains strong even though it's been cold and I use the lights and radio and HVAC fan every time I drive it. I haven't checked the alternator output yet but I would think the battery would run down if it wasn't.

I really don't know how Subarus work but is this something like a voltage regulator going bad? Are they integrated into the alternator, serviceable on the alternator when in place, remote/separate from the alternator?

Maybe a bad ground on the front headlight harness?

Bad ground on the battery? loose ground?

The positive cable has been replaced, in case that matters.

Any thoughts/suggestions?

Thanks!
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