Rough first start 2001 Subaru H6 3.0

I have a 2001 Subaru H6 3.0. I recently brought it in to a respected mechanic to check the brakes because I kept smelling burning while driving. It turned out to be a leaking right-front axle boot, so they replace the axle and boot. When I picked the car up, the engine started rough. It has continued to do so every morning (first start) since. The engine was at the low end for oil and was due for a change, and adding approx 1 qt (10W-30 synthetic) seemed to help a bit. I’ve brought it back in, but they were unable to diagnose it, and I haven’t been able to leave it with them overnight yet, so they haven’t been able to diagnose it on first start in the morning. Also, I am in Oakland, CA, and it has been somewhat cold here the past month or so. In addition, a coworker suggested it could be that the mechanic displaced the exhaust or a spark plug wire or such, but they have since checked those and in addition say there would be no reason for them to have been in the position to have done those things. Thanks for any help, I like my car and would like to get it back running nice and smooth as soon as possible.

You should have the codes read. Some places will read them for FREE. Try Autozone or Advanced Auto Parts. Get the exact code (like P0123) not just their translation into English and post it back here. It may or may not help, but it can’t hurt.

I doubt if it had anything to do with the work done, but rather I would guess it is the lower temperatures.

I agree that the lower temperatures likely have something to do with the lower temperatures recently. But, in addition, I have a suggestion that will involve going to the dealership.

With my '02 H6 3.0, I also experienced slow starting in cold weather until the dealership downloaded an updated bit of information into the onboard computer. Since this updated system information wasn’t originally loaded on my '02 model, clearly it would not be loaded on your '01 model. So, it may be worthwhile to go to the dealership and have the system “flashed” with the latest starting program.

Thanks, I’ll give that a shot and see what happens. Maybe wait til the thunder and lightening are done though.

UPDATE: I forgot to mention that I had the oil changed in the car on 1/2/08, the same time I brought it into the mechanic after adding some oil to it. So now the car has new synthetic Pennzoil 10W-30 Full Synthetic in it. Also, the engine seems to be starting better now. I’m starting think it may have been a combination of low oil level and low temperatures, but see the reply by Joseph Meehan on 1/4 for my plans for checking it out.