Odd Starting Problem

[samandw]

My 1994 Legacy Mi wagon has 207k on it and has been remarkably reliable for the entire time I've owned it. Recently, it's started acting strange on cold start though.

It will start fine, then idle down to almost nothing and sound like it's going to die. Feeding it throttle causes it to pop and stumble for a couple seconds before it revs up. Within less than a minute, it's running normally. My lame state (WA) recently switched to that E10 garbage so I'm wondering about that, and it's been throwing a code 12 "Starter switch or circuit" and 23 "Pressure sensor" code as I recall. I'm pretty sure the code 12 is due to my habit of engine out coasting and bump-starting, but who knows. Any thoughts?

[Legacy777]

Does it do this every time you start the car, or just on cold starts.

If it's just on cold starts, I'd suggest replacing the coolant temp sensor. They're about $20 from one of the online subaru parts dealers.

[SubaruNation]

maybe change the oil and O2 sensor?

and +1 to the temp sensor.

yeah that E10 will def do it.
stuff is bad news

[white91wagon]

My 91 NA wagon does this same exact thing. It gets pretty annoying after awhile. I'll start it and instantly after i have to give it a little gas to keep it running. Then after about 30 sec's or so it idles fine.
I live in washington also and have been running 89 octane gas. When i first bought the car about 2 years ago and it didn't start doing it till about 4 or 5 months later. I have also switched engines since then, and this new engine does the same thing. I think it is a problem with our fuel. I work at the local napa in leavenworth WA and i've seen many problems relating to fuel latly. That stuff is no good i hope people start realising it soon. But it could also be a sensor 2 idk.

[Legacy777]

My Legacy used to have a similar issue when it was still an auto. One a cold startup, if I started it up, and didn't touch the throttle for a little while, it would be fine. However if I touched the throttle, it would kind of sputter, and then the rpm's would jump back up.

I never really figured out what the culprit was. It was kind of hit and miss at times. It went away when I did my AWD & 5spd conversion.

[samandw]

It's got a newish O2 sensor and recent oil change. It doesn't do it every time, just now and then. But when it happens, it's ONLY on a cold start. Is the Coolant Temp sensor tied to the temp gauge? Because according to the gauge it's warming up as I would expect. Sometimes it'll also get stuck on a high idle when it's warm, and only idle down if I come to a complete stop for a few seconds, I wonder if that's related . . . or maybe it's just crap E10 fuel . . .

[evolutionmovement]

No, they're two separate sensors, but they're both on the metal coolant tube under the intake manifold.

[Legacy777]

If you don't know the age of your coolant temp sensor, I'd suggest replacing it.