I've got an 03 wrx (completely stock) and the engine often has rough idle after I start up. It usually happens when the engine is cold and I'm starting for the first time. Is this normal? Sometimes it is extremely rough like the whole car shakes (esp. when cold) other times it just vibrates a little. Anyone have the same experience?

 

What octane do you use? Have you checked your spark plugs recently? You may need to replace a fuel injector. Have you taken your car to the dealer or to an auto parts dealer, like Checker, in order to have your OBDII codes read?

 

The rough idle is totally normal. My 02 has done this from day one, and I bought it with 11 miles on it. You're using a forced-aspiration engine with three catalytic convertors, so at idle the engine is generating a lot of backpressure and not quite getting as much air as it gets while you are moving.

I love the rough idle, personally. For some reason I can't quite explain, I find it "cute." Plus, it reminds me of my dad's 911 turbo (another forced-aspiration boxer engine).

 

I always thought 911s were smooth (6cyl boxer "inherently balanced")... guess not. I think my 03 has had rough idle since day one also. Interesting.

Btw, my 03 has 5k miles on it so i don't think there should be octane issues and such. Thanks for the suggestions tho. :P

 

My dad's 911s all ran a little rough for the first few minutes after a cold-start; probably because they were grey-market (actually German Porsches) and weren't used to crummy American gasoline grades. They had a "blub-blub-blub" header sound for the first few minutes as well, until they got totally heated up. When you have a primarily air-cooled engine (the turbo had an oil cooler) it is designed to use heat to aid the combustion and exhaust process, and likes to be a specific temperature.

BTW the only rough idle you should worry about (IMO) is one that actually causes your revs to change. If your needle holds steady at 1500 (cold start) or 750 (warmed up) and doesn't wiggle, then you are fine.

 

Thanks for the tip!

 

happens to me 2

 

Nothing to be worried about. This is very typical of our cars.