Hi there, I have a 2001 mercury grand marquis LS. My check engine light turned on a while ago, got a misfire code so I replaced my spark plugs from some ngk to motorcraft. Ever since, it's been running rougher then before. I checked and know I got the right ones (although, the old ones had a much smaller gap then what my manual calls for). So my question is, can a lower quality spark plug make a car run rougher? Or would it be something else like fuel injectors? Any feedback is helpful (: thank you!
What was the exact code/s?
They actually can motorcraft or notorious for making crappy plugs these days. But of course when you change the plugs you either take off the spark plug wires or have to remove the coil on plugs and both have rubber parts that can crack and then misfire just the fact of taking them off and putting them back on can break them
The spark plugs are supposed to be gapped to manufacturers specs, no matter what the brand.
