P300 & now P303

dblwall

Original poster
Member
Dec 4, 2011
7
Have to get this beast smogged so figured I would change the plugs and clean the throttle body. Disconnected the battery, put 41-103's in it and then went about cleaning the throttle body. Connected the battery started it back up and noticed a miss. Thought maybe it was the computer relearning but nope. Shut it off, tore it back open thinking maybe a vacuum leak but everything looked good. Cleared the P300 then went to put gas in it and finally the engine light came on. Got home, scanned again and thats when it gave me the P303.

I know coils don't usually go bad just like that. Is there anything wrong with an aftermarket coil?
 

christo829

Member
Dec 7, 2011
509
Fairfax, Virginia
It's always possible that an item can be bad off the shelf, but first, make sure the coil is properly seated.
If the problem persists, swap it to another plug. If the problem follows the coil, you'll probably get a P0300 again, as the PCM will see that
the problem has moved. If it stays on P0303, check the plug. If it moves, get another coil.

There are other things that can lead to a misfire, but since you were directly working on the plugs/coils, that's the
most likely place to start.

Good Luck!

Chris
 

Playsinsnow

Member
Nov 17, 2012
9,727
I would reseat the #3 coil and see if the problem persists. If so, then switch coils with another to see if the problem follows or remains...
 

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