The '95 4Runner with 3VZE engine that I got over xmass had a loose sparkplug. Yep, loose. I was doing all the standard tests and every one was OK. I hadn't tested the sparkplug wires and sparkplugs yet as I don't like to pull them unless I have replacements on hand. Next up was to get it warm to test things when hot. So I fired it up. I'm sitting there looking at and listening to the engine as it's warming. I hear the mis and can see a very regular small shake. I look further and notice one of the sparkplug wire boots is vibrating a bunch more than the rest of them. I shut things down. Grab the boot and lightly tug. It stays on. Wiggle it, and it's obviously loose. Try to turn it, it does. It would turn 1/8 turn clockwise , and much further CCW. Then I try to get a better grip to remove it and burn myself a bit. Bloody heat shields are hot. Time to wait for it to cool. Fans are helpful. OK, I pull the sparkplug wire off the sparkplug and then try to wiggle the sparkplug. It wiggles. Go to pull it, and curse at the tight spaces. Finally get it out, looks good, gap is good, clean the plug and hole and put it back in. Check spark plug wire's resistance as I now have that one off. It's within spec.. Put it all back together and test drive. Much more power, and the mis/hesitation is gone.
According to my brother this 4runner never had any tuneups in it's entire life. It also has always passed smog fine. As for how it loosened up, who knows. It even may have never been fully tightened in the first place. The loose plug was the front passenger side one. Engine has 173k miles.
According to my brother this 4runner never had any tuneups in it's entire life. It also has always passed smog fine. As for how it loosened up, who knows. It even may have never been fully tightened in the first place. The loose plug was the front passenger side one. Engine has 173k miles.