Rep Power: 0

My 99 civic ex is idling rough, and the check engine light is flashing. It is throwing error codes P0300, P0301, P0302, and P1399. This all happened extremely abruptly.
I pulled spark plug wires while the engine was running, and cylinder 3 gave no appreciable change in performance. The engine got bogged down when removing the other three.
Should I start with a compression test on cylinder 3?
Start with cap and rotor or the entire distributor?
Can this be caused by valves or a head gasket?
Thanks

 
Rep Power: 518

No.
IF you are going to do a compression test, perform the test on all 4 cylinders. Unless #3 comes up empty during its test LOL

(Dynamic compression test: I can usually tell just by the sound of the engine cranking if a real compression test is warranted or not.)

Only if there's an ignition problem related to those parts.
When you pulled the plug wire off #3, was it sparking? Test.

Note: aftermarket reman distributors are crap.

I would not even guess at that, until I have done the compression tests and see what those results are.


Yes, but not my first suspect

Pulled spark plugs out to inspect yet? (you gotta pull all of them out for the compression test anyway)
What does #3 look like? What do the others look like?



Did this sudden poor running occur while you were driving along?
Or did it just start out running badly one morning? (mouse chewed injector wires? LOL)