Spark plug Bosch or Motorcraft
Bosch iridiums, these for longevity, copper ones have better spark if your concern is performance
Today I installed new spark plugs and the misfiring situation has improved significantly but is not completely gone. If I pull up the RPM too quickly the misfire counter goes up.
I just replaced my oem densos with some Bosch plugs that were labelled as being pregapped 1.1mm. I wanted them to be 1mm and checked with a gauge and Lo and behold they were already at 1mm. Whacked them in and improved my fuel consumption immediately.
I took it back in after setting the DPR to 2.5± 2.5 mA, checking again for any vacuum leaks, tightening down all the exhaust components, and changing out the spark plugs (again). I also checked the O2 sensor, it was fluctuating between .1v-.7v continuously.
I do run Motorcraft plugs because they seem to crack a little less than the Autolites.
Just got a Jetta again - 2010 Limited Edition just shy of 100K miles and I've got one problem with it. From a cold start, usually in the morning, the 1st 10-15 seconds run rough before settling down to idle.
I have never seen any real large difference in NGK, Denso, and Champion if the proper heat range/type plug was used.
I'm not a fan of the old platinum Bosch design or regular autolite.
I've heard for many decades how bad Bosch spark plugs are and I figured the coils would be just as bad, if not worse.
Bosch spark plugs are junk.
This is why I don't use Bosch plugs. It goes back to the quad fire plugs with a platinum center electrode that would fall out.
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