those motors are notorious sludge motors and the valve covers leaking is a lot more common than you think. the first guess was coil pack after the guy says he replaced the plugs and it wasn't misfiring for a week........if it had a bad coil pack putting plugs in it wouldn't solve it for a week. putting plugs in would not have changed anything at all.

so the 3 plugs in the back are a bitch cause the intake sits right above the rear valve cover....it'd take a NOOB C tech 6 hours. some of those v6's had 3 coil packs and 3 wires, 1 wire coming off 1 coil pack times 3.

anyways, when a person/customer says it's misfiring but he replaced the plugs and it solved it for a little while then came back, it makes no sense to condemn the coil pack FIRST or at all for that matter. it makes more sense - if you understand theory and operation - that the customers car was misfiring. the misfire was because the spark plugs were fouled out, which means most likely the plug was not getting it's ignition current. well if he put plugs in and it was STILL misfiring with no improvement at all then hell yeah i agree on the coil. but since the new plugs helped it, no. it took a week for the new plug(s) to foul out. so it's obvious there's something gradually happening with his engine that it takes seven whole days for the plug(s) to foul out....could it be oil leaking down in the spark plug tube seal? maybe. could it be a blown headgasket leaking coolant into the cylinder? maybe. could it be a burnt valve or low compression on a certain cylinder for whatever reason imaginable? maybe. but ur saying if this customer's car was in your shop and you were the tech doing the diag....your train of thought would start with an intermittent short in a coil pack....btlfed i'm assuming they're leaking, i have no idea if they are or aren't, typically when i respond on general tech i give the most likely, most common thing i see at MY shop, based on the symptom/information provided i understand you're his friend and all. green91 i'm not gonna swing all over your diag because your cosigner says you're a toyota technician. logically it makes more sense to be tube seals than it does to be a coil with an intermittent short. that's my opinion

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