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Discussion Starter · #1 ·
My mileage has recently dropped a few MPG on my 98 Trooper with the 3.5 L, and the mechanic says that the spark plug wire/boots are worn, allowing some arcing to the head. He also says that the only way to replace them is to by 6 new coils, which include the long boot that goes to the plug (about $200 x 6!).

There's got to be a better way. Does anyone have any experience with this problem?

Thanks in advance,
Brian Meyer
 

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My big question would be:

How does he know it's arcing? Unless he's saying it's arcing on the top of the coil (unlikely)

The only way this could be seen is if there is eveidence inside the chamber where the plug boot goes into. If this is true it's the first time I've heard of such madness.

And the boot and the coil do come apart. Maybe St. Charles Isuzu can get you just the boots. 1-800-727-8066.

Joe
 

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I agree with Joe. Those little wires are low voltage until they get to the coil paks, so they can't arc. The only high voltage part is under each pak, which is pretty well protected and usually in good shape unless previously damaged during plug replacement.
 

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Find another mechanic. As said above - no way he would be able to know this for sure and the new setup being used these days isn't likely to have this problem.
 

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My co-worker has a 2003 Mitsu Lancer; they have almost the same setup where the coil is over the spark plugs on two of the cylinders.

He started having problems with the engine where the engine would start to hesitate a little.

He looked at his spark plugs and he noticed that one had a crack on the ceramic part of the spark plug. He replaced it with a new spark plug and everything went ok.

After a short time the problem return. After checking the sparkplug it had a crack again. After checking with a mechanic, it looked like the boot had a crack in it that was causing the arc in the spark plug chamber.

They replaced the coil and the problem when away. I saw the boot with the coil attached and the crack in the boot is very hard to see.

I also think that the gas consumption problem might be else ware unless your noticing problems with your engine.

I also started to get bad mileage on my Trooper; it had dropped to an average of 14-15 mpg. Last month my check engine came on and reported that one of the 02 sensors was bad. I replaced two of the o2 sensors and after driving it for a while it looks like its getting better gas mileage. I will be replacing the other two next month just to complete the swap.
 

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Yeah that would be my other tip. Take the 8mm bolts out of the coil packs. Then pull the coil pack off of the plug. Inspect each one of them bend the rubber boot in different directions to see if you can find a crack.

I know the boot and the coil pack come apart. You really should be able to buy just the rubber boot, not the whole coil pack. If not maybe a junkyard trip is in order.

Joe
 

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I am having a Cyl 2 Misfire code. I had it tested by Autozone. Those guys first told me that it's the Spark Plugs and that I should only use the Denso Iridium Spark Plugs ($12.99 x 6) for my Rodeo. They swore that I would see a difference and that the light will go away. I have bought those and saw absolutely no difference. My CEL is still on. :x

I went to another AutoZone since there are about 4 in my 15 mile range. One Mechanic was very knowledgeable. He unplugged the wire that connects to the Coil of the 2nd Cyl and there was no difference in the way my Rodeo worked. He then unplugged the one for the Cyl 6 and the engine sounded like it was very low on power. I then swapped the Cyl 2 coil (bad) with the Cyl 6 coil (Good). Now the CEL showed Cyl 6 misfire.

You can buy the coils for $89 at AutoZone.

Good Luck.[/b][/b][/b]
 
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