It's hard to check spark plug wires with an ohm meter. Basically, anything above 100k is "broken" but below that is fine. If the wires are working, why do you want to fiddle with them? I have the same mileage and have never changed plugs, wires, distributor cap or anything. I hit 27+ MPG on the highway. "Ain't broken, don't fix it."
Dont play games , replace them, have you ever checked the rotor or caps carbon tracking, im sure not, replace them. Have you ever checked timing, I bet not, You will get 3-5 mpg better when you learn to care for your car.
That's a bold claim. I have never had that kind of reward for replacing anything except parts which made a car run noticeably badly, sometimes not then. Especially these days when ignition components are less critical than they used to be.
adjustment a quarter turn and the computer turns it back a quarter turn.
The shotgun approach -- replace everything in hopes that it will fix something is not very sophisticated and is certainly not economical. If your car doesn't run right, diagnose it and repair what is broken.
4 hours for rear bank plugs is a bit long. You should be able to reach all plugs from the driver side, using no more than either 3" or 6" extension (yes, just one at a time) with a spark plug socket and a standard 3/8" ratchet. No need for u-joints on the extensions. You may prefer to remove the PCV valve and hose from the manifold instead of getting the right most plug from the driver side. Shouldn't take you more than 30 minutes. The fronts ones I'd say no more than 5 minutes or
10 if you work slooow ;)
The timing belt does stretch with time reducing mileage and increase emissions. If you do your own work I'd say change it (and the pump, pulleys, seals) at 60K miles. 90K miles is a bit long.
Today's timing belts do not use steel cords. They are types of kevlar cords. Toyota had years of problems with the 5SFE belt stretching to the point of slapping the timing cover until they updated the belt around 2001(?). So timing belts can strech and they can strech baaaad.
There are of course other cord materials, like the Gates' carbon cord composit belt developed for Harley Davidson. Hardley wanted to put a wider wheel on their bikes, and instead of using metal chains Gates was asked to come up with the world's first commercially successful "carbon cord elastomeric composite belt". It's a thin belt with the strength of metal chains.
While some belts are spec'ed to go over 100,000 miles (like the Gates timing belts in Hondas), I do my own work and would change them out at
60,000 miles. $30 for a big rubber band is cheap (plus other usual parts for a timing job of course).
I have a preference for Gates Timing Component Kits. They include the idler and tensioner pulleys.
That's not surprising since carbon composites are used in place of steel wire rigging for instance, for its higher tensile/lower stretch. My point is if a belt stretches you've got bigger problems than spark timing.
That's why I like Gates timing kits. It comes with two pulleys, an instruction sheet by All Data, and an excellent timing belt. In fact, when Toyota was trying to figure what was wrong with all those timing belts stretching, they asked techs to replace with only Gates timing belts!
Yeah, the timing light does tell only what the CRANK timing is, but it won't be able to tell you if the CAM is off relative to the crank because of the stretched belt.
It's been reported that when the belt stretches to a point a tooth will land right on the ridge on the sprocket and the belt will snap cleanly at that point.
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