Hello

When I started my '04 R53 this morning, it had problem starting but once the engine started, the SES and DSC light came on. I also noticed it was also sputtering out of the exhaust. I turned off the car and tried pulling the code with my OBD II reader and a P0302 came up (cylinder #2 misfire). The DSC light went away the second time I started up the engine. In addition, it was raining here in Los Angeles for a couple of days last week. The car was sitting in the garage all weekend. Could moisture have something to do with this? So I would like to know if there is a checklist items I should check off in order when trying to diagnose the P0302 issue.

thanks

 

moisture? doubtful
check oil/coolant levels. cars do weird things without these 2 items.
next check ignition track:
ignition coil contacts/condition. If rusty, the wires are also likely rusty and will cause misfire. my recommendation is MSD coil + MSD wires. If you already have the MSD coil, I've still seen a few older MSD units fail. so dont check that off the list just yet.

check spark plugs. they should have less than 60k miles on them. the ground strap should be in tact (not missing or burned off) and porcelain near the top tip should be brownish/white in color and gap should be close to spec (increases as plug ages). It will be likely that your #2 plug will be a bit fuel fouled if the car was badly misfiring.

If these things are good, the next easiest thing to do while the plugs are out is check cranking compression. do this with a friend who has their foot on the floor. let the gauge flutter precisely 5 times and check the reading. the stock range is very wide- something like 130-190. most of them i've checked have been 160-170. You should not have more than ~10 psi difference between cylinders. If these numbers are significantly lower, your car may have suffered some engine damage. You can also perform a running compression test. do this with the schraeder valve removed from the gauge and the engine running. during each test. The maximum PSI achieved should be = 80% of your cranking compression test results.

if all these things check out, I would be looking into the fuel injectors and possibly the DME (engine computer). DMEs are very common failure in the R53.