[Zen31ZR]

Do a compression check. When you pull the spark plugs, make sure none of them are fouled. Compression should be between 125-150 psi depending on your altitude and engine condition. No lower than 120 psi and no more than 10% deviation between cylinders. If you don't have a compression tester, one can be had from almost any local auto parts store for $16-$30. I paid $17 for mine and it works perfectly.

 

[Zen31ZR]

You're doing the compression check without the car running. You have to disable the fuel injection, and the spark, because you will still be cranking over, but you will not be running it. This will help you determine what is going on in the first 2 cylinders you say don't affect the cars running ability. You'll be able to find out if maybe the Hgs are blown or if maybe the plugs are just dead or what. If you don't have the first clue about doing a compression test then you should take it to a mechanic. A Z31 isn't really for a beginner to work on, they have their own little details you have to work around.....