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Subaru Outback - Cold weather starting issue

My current problem is that my Outback (92K miles) has begun to not start reliably when the temperature is cold. It's a 2.5 XT (Turbo). I first noticed it following a freak October ice storm. It also happens if the car has been allowed to sit in cold weather (below 35 degrees) long enough to cool down. If the weather has been cold overnight, when I start the car, it starts ok, but after mabye 15-30 secondst the idle settles in at around a wobbly 900 rpm and the car idles very roughly. If I attempt to drive it, the car will not go above 10 mph. I can let it idle like that for a period of time, but it doesn't improve. If I apply gas while in park, it will rev no higher than 1200 rpm. However if I turn the car off and then come back maybe 10 minutes after it starts ok most of the time and then drives ok. I also get a check engine light and the cruise light The dealer says the cruise light indicated that when I have a check engine the cruise is disabled. When my dealer checked it, the codes indicated some throttle body issue. (A friend with a home diagnostic unit also checked and the problem indicated had to do with a throttle body actuator.) How that could be temperature related I’m not sure but the service manager suggested cleaning the throttle body. That was his cheapest guess. The cleaning ran $160 and did not fix the problem. So that appeared to be a cheap guess and I’m out $160 with no value to me in terms of anything being fixed. The service manager’s next two best guesses were to replace the throttle body altogether and if that didn’t work, then maybe the ECM was sending bad codes and might need replacement. When I asked what those actions would cost his estimate was that each action would run around $1000!!!!! Simply put I am not in a position to pay $1000 a whack to have that service group check their guesses. If I’m going to pay $1000, I expect some assurance that the fix will clear the problem. Or that if it doesn’t I’m not going to pay $1000 for the effort. For example, I cannot believe that there is not a way to check the ECM to find out if the one that’s in there is working right short of putting a new one in. As things stand now, the service manager suggested I “live with it”. I also did a web search and this location had a similar issue, but did not appear to be temperature related.

Any suggestion would be valuable. The website I referenced claimed to have some success with replacing a relay behind the glove box, but I can't believe that something in that location would be affected by 30 seconds of idling in cold weather. Looking ove the Cartalk web issues, I could maybe believe that a sensor may be bad, maybe a temp sensor. But I'd like some backup on that. I di dnotice that my temp report on the dash has seemed to lag real life a good bit, but I noticed that when the car was actually running ok on the road.


  • Post the very exact and specific code(s) pulled from the computer. The format is "P1234"
  • We are on our eighth Subie (3outbacks, 4 foresters & 1 Imprezza). Never had the problem AND never lived where 35F was cosidered cold!
  • I've a 02 outback 2.5ltr with 190K. I have had a similar problem usually related to cold, wet and when I park it outside in those conditions. Since I usually keep it in a garage it does not present much of a problem and I just live with it but think it would be major if I did not have a garage. Not sure what causes it; suspected cracked spark plug wires, changed them but no help. If it had an old fashioned distributor I would suspect a cracked cap, is there something in an electronic ignition that could act like a cracked distributor cap?
  • rajraj Duct Tape Specialist
    edited February 2012
    Check out , your vehicle has exact engine. I had problems starting my wife's car(05 Legacy GT) and searched here and ran across a thread about what you experience.

    There are some o-ring gaskets that sit under intake manifold that likely need replacing. Search within that site.

    update visited site related to my issue and found this:

  • I would guess the throttle position sensor may be causing the trouble. You can monitor the 1-5 volt signal to the ECU to see if that is the trouble. The voltage should vary as the throttle position changes. Try cleaning the EGR vavle also. They get clogged up over time.
  • Wow! Thanks for all the inputs.

    Rtjny99, yeah 35 isn't all that cold, but it's a range where the problem seems to crop up. In fact I'm in MA and I get grief for complaining about the lack of snow this winter.

    cigroller, I need to get back to my friend with the code reader but I'm sure one of the codes was one of the ones in thelink I posted. That code was P0638 "Throttle Actuator Control Range / Performance (Bank 1). I can repost tomorrow hopefully.

    Raj, I'll check your link as well. Thanks again.

  • I fianlly got my car back to my friend with the analyzer and the only code showing was indeed P0638 "Throttle Actuator Control Range / Performance (Bank 1)." I googled that text directly and there's a ton of discussions about the problem. I'll need to take some time to review them. One annoying aspect of what I looked at so far is one thread that presents a diagnostic approach for the code.

    The dealer never mentioned trying to diagnose, but went directly to guessing about replacing whole components, like the throttle body and ECM. Maybe I'll take it up with Subaru America.
  • edited February 2012
    As I mentioned before, I would check the throttle position sensor. The internal contacts may be dirty.
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