[dyang]

Hello,

Yesterday I've changed my spark plugs with Bosch ones from NGKs, I've also changed the ignition coils. However, I realised that the fuel economy has become worse, the power has also been reduced. Today, I've checked the spark plugs and they weren't torqued enough. I accidentally torqued them 17 Nm instead of 23 Nm. The tip of the spark plugs became black and one spark plug had deposits on it. After reseating them, the engine started misfiring. What could be the cause? Did I overtighten them?

[smokinu454]

not likely you caused a miss by under tightening unless compression could escape around the plug, not likely that tightening to spec would cause it either. Id lean towards you installed a bad plug or coil. Datalog and see if there is indeed a misfire, if its on just one cylinder I would i would swap the plug and or coil to another cylinder and see if the miss follows to that cylinder. also make sure you plugged all the coils back in at their correct cylinder.

[dyang]

Originally Posted by smokinu454

not likely you caused a miss by under tightening unless compression could escape around the plug, not likely that tightening to spec would cause it either. Id lean towards you installed a bad plug or coil. Datalog and see if there is indeed a misfire, if its on just one cylinder I would i would swap the plug and or coil to another cylinder and see if the miss follows to that cylinder. also make sure you plugged all the coils back in at their correct cylinder.

Indeed, there was a misfire on cylinder 3, I also got the error mixture too lean, could that be a cause for concern? I also replaced the new ignition coils and spark plugs with the old set and I still got a misfire. Tomorrow I will swap ignition coils and then check whether there are still misfires.

[iverson03tj]

Could be injectors. You could also try resetting adaptations.