I let the spark plugs go too long on two different vehicles over the years...a 2003 2.5 H4 Subaru Baja and a 2005 4.0 V6 Ford Explorer. The symptoms were basically the same. Engines started vibrating under 2000 RPM, very low power, no acceleration.
What I'm curious about is both times, the check engine lights did not come on and no codes popped even though the engines were running like crap.
When I got the old plugs out, the gaps were huge with not much of the tang metal left. Both cars ran great after the new plugs were installed.
Why didn't the sensors/ECMs indicate anything? Not even a misfire.
Well the computers aren't that good and even though it's supposed to trip a misfire they often don't win the spark plugs wear out basically check them every 80 90 thousand Miles and if they're worn replace them
