Hello I have a 08 r56 with almost 80,000 miles. And I'm having a ton of issues and I really need someone to help me to decide what to do. I bought the car private party without any knowledge of any issues minus the water pump leak. Didn't seem to bad until two weeks later. Idle became rough. Through my own research I concluded the pcv valve and cover were needing replaced along with regular tune up. New coil packs new spark plugs new pcv valve and air filter and an oil change. Mini runs great for one day and then boom misfire in all cylinders and a random one on my OBD2 reader. It has not stopped misfiring but now I'm getting different codes for my passenger window, HVAC system, and some I haven't been able to figure out. The car runs CLEAN minus that. It definitely misfires on idle but I'm just so lost. Also I am aware that the therm needs replaced as well as the pump and I'm gonna do the belt and tensioner. Also prepare myself for the death rattle. I just need so help if someone wouldn't mind I am about to pull my hair out

 

How old is the battery? And I’d check for loose or corrosion on the engine grounds.

 

I believe the PCV valve, if installed incorrectly, will make the engine run a little rough too....I somehow screwed mine up and discovered that!

 

Random and hard to pin down rough running can be a PITA and tough to diagnose.

IMHO, the way to diagnose is to start with your charge pipes/air intake tubing -- that's all the piping from the front of the hood near the coolant reservoir, through the air filter and then (going counterclockwise around the engine compartment) from the throttle body on the passenger side of the intake manifold along the side of the fender and then down to the intercooler. Make sure all those are tight and not leaking. Also check the big rubberized plastic piece running between the turbo and the air filter, and check the MAF which is right there, too.

Then check the vacuum lines running to the turbo and wastegate.

Next, check the PVC line running into the back passenger side of the valve cover gasket. At 80,000 miles you should expect to replace it if it hasn't been lately. To do that you'll have to pull out a bunch of stuff including the intake manifold, so if you don't have to replace it right now don't do it yet.

Next check coils and plugs -- you can check your coils by swapping them around, usually, and view plugs via physical inspection. While you're in there, pull the valve cover and check for leaks there -- reseal or replace the gasket.

If nothing is obvious after doing all that, I'd start with checking the throttle body.

That's the order I'd look at things -- going from cheap and easy to more involved and more expensive.

If none of these work, I'd start looking at the intake valves and check for carbon build up -- these engines are notorious for it and it can be a real serious problem. Lots of threads here about how to proceed.

Get the water pump, thermostat and crossover pipe done ASAP, and make sure you check timing chain tension to make sure you don't get the death rattle. Good Luck!

 

Please have the battery and alternator tested. If one or both is weak, then misfire codes will become pronounced and will wreak havoc on interior electronics. Also, a loose battery connection will do the same thing.