Hey, I'm new here and got my first Audi a couple months ago. It's a 2001 Audi A4 1.8T with just under 87k miles on it.

Well I changed out the oil (I used Syntec 5W-50) and put a new, slightly larger, FRAM oil filter on and didn't mess with anything else. I turned the car on and it starts to sputter and shake pretty violently but only in idle. The RPMs will jump from .5 - 1.5 pretty randomly and if it idles long enough the CEL starts blinking. Everything seems to go away when I'm driving it around though.

I'm waiting on a friend so I can go pull some codes but any ideas?

did you drain the right fluid? check your MAF and intake piping

Yeah I did and the MAF was just replaced.

a blinking engine light means misfires. since you have a 01, theres really only 2 things that can be bad. spark plugs, and ignition coils

Pulled codes for the first time and got misfires on all four cylinders, system too lean, and a bad O2 sensor. We reset the codes then messed around with the engine for a little and only two misfires this time.

Would the misfires account for engine shake? There's also a loud hissing and clunking when the car idles. Is a vacuum leak a possibility?

I know this probably wasn't a smart move when I bought the car but I never checked the various fluids and today I noticed the engine coolant wasn't green at all. It was an off-white almost milkshake looking color.

misfires cause shakes, it sounds to me like you have a bad boost leak somewhere. and coolant in these cars should be pink, and only pink

Ah alright, thanks for the information. Looks like I'm bringing it into the shop tomorrow for a diagnosis and hopefully it'll be something I can fix myself.

just stick your head in the hood and listen for a hissing noise and pinpoint it

Check your ignition control module. If you have a buddy with an A4 you can borrow theirs to swap into yours for a sec. On the 1.8T its on top of the airbox, secured by two screws and connected by two wire plugs. Mine went bad, had flashing CEL (which means the exhaust is crappy enough to foul the cat) and I spent a lot of time fixing things trying to find it. Try this before you take it to the shop and spend more money. Worst case is you find its not the ICM and you take it to the shop anyway.

kayak, 01s dont have ICMs