Paul Bruchal Posted March 5, 2012 Share Posted March 5, 2012 Which are the best for 90' 4.0? NGK E3 ETC? Link to comment Share on other sites More sharing options...
Geonovast Posted March 5, 2012 Share Posted March 5, 2012 You should be good with anything with a copper, single spark. Link to comment Share on other sites More sharing options...
Paul Bruchal Posted March 5, 2012 Author Share Posted March 5, 2012 I'm not saying your wrong, but why is that better? Link to comment Share on other sites More sharing options...
Pete M Posted March 5, 2012 Share Posted March 5, 2012 because other guys have had issues with the fancy ones. the jeep engines just seem to like plain ol' copper. :D Link to comment Share on other sites More sharing options...
dave92cherokee Posted March 5, 2012 Share Posted March 5, 2012 The most reliable ones in our engines from 87-98 are the traditional champion copper plugs part number 4412 which are discontinued so now they're just 412. For the 99+ group alot of people use NGK iridium I believe due to the changes in the ignition system. These 4.0's we have prefer to be old fashioned and these new fancy v power, +2, +4, all that causes problems with engines resulting in detonation, knock, and other issues as well. Link to comment Share on other sites More sharing options...
dasbulliwagen Posted March 5, 2012 Share Posted March 5, 2012 Being in a Jeep dealership we see these problems too with the fancy spark plugs in 4.0's just get the coppers, youll be fine, and the engine will be happy. Link to comment Share on other sites More sharing options...
'87 fuel-miser Posted March 5, 2012 Share Posted March 5, 2012 just went through this with my 4cyl / 4 sp ... plain 'ol ac copper ! don't waste your $$$ on expensive ones ! :thumbsup: Link to comment Share on other sites More sharing options...
carnuck Posted March 8, 2012 Share Posted March 8, 2012 Autolite or NGK for me Link to comment Share on other sites More sharing options...
FrankTheDog Posted March 8, 2012 Share Posted March 8, 2012 Stock champions every time. Never any trouble. Every time that I tried something else it has ignition issues. This was with several 4.0's from 88's to 99's in MJ's, XJ's and ZJ's. Link to comment Share on other sites More sharing options...
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