chibitul wrote:
> Hi,
>
> To make sure all 4 cylinders are running, I unplugged the high voltage
> wire from each spark plug (one a a time, not all at once). Each time
> the idle RPM dropped a little bit, so I said "OK, each cylinder must be
> firing properly".
>
> However, I drove later to AutoZone and asked them to check the error
> codes, and there were NONE! not a single error code. So why there were
> no error codes? Also, with one wire unplugged, the Check Engine light
> did not come on (the lamp is OK, it comes on at start-up).
>
> All this is for a 97 Civic LX by the way.
>
> Thanks
>
what problem are you trying to diagnose? plugs are so cheap, if you
have any doubts, just replace them.

regarding codes, fwiu, you /should/ get a code from a "misfire". it's
detected by registering a change in the angular velocity of the
crankshaft and should indicate /which/ plug is misfiring. but the ecu
may not trigger a misfire code below certain revs or maybe if it's not
misfiring for very long - just guessing because idle can give erratic
crank rotation speeds hence the need to not be too sensitive and plugs
self-clean when hot, hence the need to ignore any misfire when still
warming up...

if anyone knows for sure, please post.