So I did something stupid. One night I came home late, my buddy dropped me off. I noticed that my interior lights were on. I decided to start my car to recharge the battery. I figureed I’d give it some time to run and went inside. I fell asleep and the car ran all night and into the afternoon (just idling).
Despite my fathers ranting and ravings, my car ran fine… for awhile. After a few weeks, when I started up in the morningd the engine temperature sensor on the dash would take awhile to get off of cold. A couple days later, it began to run rough and the check engine light would flash. We changed the thermostat and the coolant temerature sensor. The car is still running rough and the check engine light is still going on. We had had the car hooked up to a computer, but our mechanic said that it didn’t show anything conclusive. What do you think we should do next.-- Thanks-- Matt
Hook it back up to a computer(auto parts do this free many times) and post code(s) here. You are shooting in the dark throwing parts and ideas at it.
A steadily illuminated CEL means that the engine should be checked as soon as it is convenient.
A flashing CEL means that something is seriously wrong and that the vehicle should not be driven anywhere except directly to a repair shop.
As to what is causing the problem, there are a myriad of possibilities, but allowing the engine to idle for an extended period of time is probably not one of those possibilities unless perhaps it led to fouled spark plugs.
Since this is clearly beyond your mechanic, I think it is obvious that you need to seek someone more experienced with Subarus in particular, and with diagnostic work in general. In this situation, the dealership may be your best choice, given your mechanic’s lack of expertise.
Bear in mind that whatever is wrong will not get better and can actually result in a cascading sequence of problems with ever-mounting repair costs. Also, the engine is probably using more gas than usual and is emitting more pollution than is normal.
There is no reason to defer the necessary repairs and there are scores of reasons for doing it now.
I don’t think the extended idling caused the problem. Cars with cooling systems in good order should be able to idle for a LONG time without damage. Did the engine overheat while you slept?
Without knowing what the trouble codes were it’s hard to even guess what the problem might be. Did your mechanic tell you what the codes indicated?
“Nothing conclusive” is not a trouble code I’m familiar with.
Are you sure about what the lights mean? I probably should mention that the lights flash then go out… there isn’t consistent flashing… I thought I read in the book that steady light as the one that indicated bad news
yeah I guess Im going to have to go to the Subaru dealer… the guy said that he had a Snap on machine that doesn’t pick up all of the subtler trouble codes
Let your mechanic off the hook. He’s really telling you that he doesn’t know what to do. The excuse is just to save face.
A good mechanic can be found outside the dealership. Some people get it into their minds that a dealership, for a particular make, has better mechanics for that make. 'Tain’t true; but, you do have to ask around to find a good mechanic/diagnostician.
Yes, I am sure. I would suggest that you read your Owner’s Manual, which is fairly clear on this topic.
I probably should mention that the lights flash then go out… there isn’t consistent flashing…
Yea you should have. 
yeah sorry about that… its all fairly moot now, as of this morning the CEL is on constant
Yeah, our regular body man usually refers people to this guy… the other thing is b/c like I said above the light had been goin off after driving for a little while, when I went there the light had not been on when the mechanic hooked it up, I might give him another shot today now that the light is on constant now
the code he got was a PO304 Misfire Cyndiner #4 Detected, I changed the spark plugs 10,000 miles ago. He said when he looked under troubleshoot it mentioned the EGR valve (anyone know the likihood of that being the problem? and how much it would cost for the part… none of my local auto part store sell it)… the also unplugged the valve and I saw that the engine acted pretty much how it does in the mornings- same sort of rough shaking… there were also other codes that came up, seemingly as a result of unplugging the EGR valve- P0100, P0101, P0115, P0125, P0201, P0202, P0203, PO204… lastly when he was looking at the 4th cylinder, he got shocked in a place he said that there shouldn’t be a shock and thought perhaps something was going on with the coil that shouldn’t be… Any knew insights you guys can provide will be great— you’re previous ones have been invaluable already