Very very bad surging on cold starts, only sometimes

I went to start up my car (stock 2008 legacy gt) to go for a ride, and the engine was very erratic during idle.

 

The car started fine was I idling at around 1,500 rpms after a few seconds it jumped up to around 2,200 rpms, then dropped to around 400 rpm about to stall, and it stayed like that for a few seconds jumped back to around 2,200, then dropped back to 400 after the engine warmed up just a little bit (Maybe a minute or 2) the idle went back to normal.

 

This is not the first time it has happened to me, but it only happens when it is below freezing outside.

 

Any advice?

Sounds like a stereotypical vacuum leak. Odd with the temperature thing, but I'd recommend taking it to a speed shop that deals with turbo cars or a shop that works on a lot of turbodiesel trucks and having them do a boost leak/vacuum leak test to see where it's coming from. It's pretty normal a car that old starts to have a few leaks.

not a great video, but it shows what is happening a little bit. Now to remind you, it only happens when it is below freezing, and only for the first 2-3 minutes of a cold start, warm starts a fine, when it warms up it's fine.

Worst case would be those big o-rings between the intake manifold and the TGV's.

 

I have heard some had to replace them on 08's.

 

I had to remove the black ones my 05 came with and install the larger orange ones. years ago.

 

You can do it by removing just what you have to to lift the intake manifold the 1/4" or so to get the old ones out and the new ones in. Just look things over and see what you need to remove or loosen. I did one side at a time. That was back in 2010 or so.

 

Another way would be to remove the TGV's from the head and other things you'd remove to get the intake manifold off as if you were replacing the engine. Then replace them on a bench.

 

Hopefully its something simpler then that.

Ah, yes, Max is probably right on here. Intake manifold gaskets failing typically exude symptoms like this in the extreme cold.

After I got my spark plugs and valve cover done this issue seemed to go away.

 

Now I gotta figure out where did all my coolant go from the time I dropped it off at the shop and picked it up? I am fuming

I would wager it's because they unplugged the battery to get access to your driver's side plugs. The issue will come back.

Possibly, but the issue didn't go away when I had to swap to a new battery.