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2010 Legacy GT Stalling When Cold


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Car starts fine, I don't notice any particular problem with idle. If I am driving before full warm up when the heater kicks on, it has started to stall when i put the clutch in and the idle drops down. Once the heater is kicked in and the car is fully warmed up, it has never happened. We parked and ate lunch, went grocery shopping, and it was fine afterwards as well. I'm going to have to start doing a full 5-10 warm-up to be safe, but I'd like to fix it because that's mostly a waste of gas.

 

 

 

I did some searching and it seems like it could be IAC, vacuum leak, or MAF, but all of my search results were on 4th gen vehicles. Has anyone experienced this issue yet on 5th gen? My car is up to 151k on the odometer.

 

 

Thanks

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I would start by cleaning the MAF and catching up any other maintenance that hasn't been performed. Have the plugs been changed? PCV valve been changed? A good inspection of all the hoses, there are dozens. Maybe even a throttle body cleaning if everything else checks out, and you may also want to check the inlet to the intercooler for oil to see if maybe you aren't having a lot of blowby picked up by the PCV system.
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  • 3 weeks later...
  • 2 years later...
Well, this saga continues, time flies when you're not driving your car much. Current update is the issue came back, they replaced a coil that was misfiring and then a damaged spark plug. They've had it for a couple weeks and have been unable to find anything wrong. It continues to stall when cold and does not throw a code. They are telling me the next step in the process is to pull the valves (engine) and it would be a $1900 cost, yikes. The car is only worth around 4,000 so that's probably a no. I am still posting here just to see if anyone else has had any issues similar to this, and if they found a resolution.
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It is plausible that the valve clearances are really low and one of the valves isn't closing completely. If this is happening, it will burn a valve pretty quick.

 

 

They claim they are finding nothing at all in compression tests showing that there is an issue with the valves but there is some potential valve issue that could only be showing up when it is cold. It just seems a bit unlikely to me, definitely not going to spend the 1900 just at the chance this is the issue.

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were they able to replicate the issue? if so they should have been datalogging to figure out what was giving it issues.

 

if you had issues with the throttle body before my gut says to look there...maybe something internal is slipping and opening too much/too little on cold starts, and when it warms up it everything expands and doesn't slip. i haven't taken one of these apart to know the inner workings of the TB, but just a thought.

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were they able to replicate the issue? if so they should have been datalogging to figure out what was giving it issues.

 

if you had issues with the throttle body before my gut says to look there...maybe something internal is slipping and opening too much/too little on cold starts, and when it warms up it everything expands and doesn't slip. i haven't taken one of these apart to know the inner workings of the TB, but just a thought.

 

 

Yes, they explained they had done extensive testing, they've had the car about 2 weeks now actually. Said my current cost is 0 dollars actually. They had two techs in the car duplicated the stall with no error issues on an live logging laptop. I am considering asking for a quote for a new throttle body and replacement PCV valve. Vacuum has been checked already as well though with no issue, fuel pressure no issue, throttle body cleaned. Plugs checked, (about 40k miles on them) They are getting valve check recommendation from some engineering service for Subaru maintenance.

Edited by TheCopyCat
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Well, throttle body is like a 660 dollar part, so replacing that on a whim isn't viable. It looks like I am stuck with the option of having them adjust the valve lashing. In some googling it is something that is done on these 2.5 DOHC engines and there are some videos on how to do it, problem is they have to pull the engine to do the work so it's a $1900 job. I am trying to talk myself into the job with more research. I really don't want to replace the car now, still seems fine other than this issue, I WFM and drive it minimally. A frustrating predicament.
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i know you don't want to throw the parts cannon at it, but you can pick up a used throttle body for $50 or so...

p/n 16112AA310

https://www.ebay.com/itm/322408598646?hash=item4b110ccc76:g:qw0AAOSwX~dWqPAh

 

 

 

 

Very tempting, but think I've decided to live with it for the time being. I checked carfax records on service and I've only driven about 11k in the last 2.5 years. Work from home life is pretty nice.

 

 

 

It just doesn't make sense that the throttle body changes temperature enough when the engine heats up that it would fundamentally change the operation. I'm considering investing in a code reader to reset CELs if I get one due to this issue.

 

The dealer quote for valve adjustment on this car was $1,920.00. Local shop I trust said they wouldn't bother taking it on, and if it doesn't fix the problem then you'd be SOL at a smaller shop, while at a dealer they'd have to liable if it didn't fix the issue.

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keep in mind that there are electronics in the modern throttle bodies - if you have cracked solder joints or damaged traces, it doesn't take much temperature to result in a pretty large change in electrical behavior (maybe going from a decent connection, to one that become intermittent) so I wouldn't rule it out - in a 2010, you are looking at an electromechanical bit that has seen 12 years of heat cycling, extended time at engine temperatures, etc. - it's hard on things!

 

 

valve adjustment is expensive because to "adjust" you need to pull the cams. What would they charge to just check the clearances?

Edited by DrD123
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keep in mind that there are electronics in the modern throttle bodies - if you have cracked solder joints or damaged traces, it doesn't take much temperature to result in a pretty large change in electrical behavior (maybe going from a decent connection, to one that become intermittent) so I wouldn't rule it out - in a 2010, you are looking at an electromechanical bit that has seen 12 years of heat cycling, extended time at engine temperatures, etc. - it's hard on things!

 

 

valve adjustment is expensive because to "adjust" you need to pull the cams. What would they charge to just check the clearances?

 

 

The thing is the throttle behaves basically the same each time. I there is a setting in the ECU code where after you start driving warm up mode ends. Once it's warmed up and you let off the gas the engine goes to approx idle, 700 rpm. When my car is cold it goes to 700 rpm and dies instantly. I was considering testing the throttle body theory with a heat gun or hair dryer to warm it up before the rest of the engine.

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