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So I figured out what was causing my random miss. It turned out that the middle cylinder on the passenger side had a melted spark plug. The anode was completely gone and the electrode was in pretty bad shape too.
It was an Autolite AP765 (correct OEM platinum plug for the 4.0) that had been in the engine for about 10,000 miles. The plug wires were really old crap from autozone. The one on that plug measured 3K ohms with the multimeter.
I replaced all the plugs with autolite 765's (plain resistor plug) and installed a set of Bosch premium wires with dielectric grease on both ends.
What could have caused this? I should mention that the truck has been running great with no audible detonation. With the new plugs and wires it makes good power and drives fine. I'm just wondering how long the new plug will last.
It was an Autolite AP765 (correct OEM platinum plug for the 4.0) that had been in the engine for about 10,000 miles. The plug wires were really old crap from autozone. The one on that plug measured 3K ohms with the multimeter.
I replaced all the plugs with autolite 765's (plain resistor plug) and installed a set of Bosch premium wires with dielectric grease on both ends.
What could have caused this? I should mention that the truck has been running great with no audible detonation. With the new plugs and wires it makes good power and drives fine. I'm just wondering how long the new plug will last.
