I've got a 91 XJ. When cold it has problems idling (whether in gear or not). After about 15 minutes the idling problem disappears. Last time I checked the plugs, the frontmost plug was in bad shape the electrode was nearly worn away, I managed to gap it, but I really should've replaced it. Could this be the problem?
I wish I knew how that one plug got so eroded while the rest looked great. I guess I'll replace it tomorrow. Autolite's your recommendation then? The other plugs looked great so I shouldn't have to replace them.
Sometimes plugs are defective from the factory. The other thing is plugs for 1 and 6 get the least amount of cooling from the water jacket. What will cause the electrodes to erode is pre-ignition/pinging and that can be caused by hot spots, carbon buildup, faulty injector. I'm betting that the sparkplug was shot and it was causing the problem.
If you replace plugs you should replace them all. They are cheap. Getting at #1 will require a swivel socket. And use a torque wrench, plugs go to 25-30 ft.lbs.
Depending on how old your rotor, cap, and wires are you should replace those too. If you need a reference here is a ref.
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I like autolite but there are others including Champion. The splitfire/iridium/ multisparkomaticmakeyoursledarocket plugs are junk.
The plug wasn't number one, it was number two (counting from the front of the vehicle, in ascending order). This plug was the ONLY plug that was different from the rest. It was a Champion 4412 and 1/4 (at least) of the electrode was completely worn away. The other plugs are all Autolite 985's. I'm thinking the stealership had something to do with this, because I normally use Autolite 985's. I'm wondering if they might have put in a used Champion 4412 for some bizarre reason. The SUV starts, but I'll have to see if this clears up my idling problem. If not, it's on to the TPS and throttle body for some cleaning.
Give the guy some time. I have a coworker who bought a new jeep and wouldn't even drive the thing in the rain for a month or so. Now he is complaining because he bunged up a skid plate taking a "shortcut" at too high a speed last weekend.
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