My 1999 Deville (The Bop Mobile) recently started running rough.
I ran a couple of bottles of fairly expensive injector cleaner through the gas tank and the problem seemed to go away.
A few days ago when I fired it up, it started running rough again even more pronounced than before.
Code P0300 seems to be the culprit. (random misfires)
I pulled a plug and it had a white coating on it. (running lean)
I checked and replaced the somewhat clogged fuel filter.
Problem is still there.
Dead battery this morning also.
Any Ideas? The car has 78k on it.