grantman18

The fuel economy on my '00 Sport seems low so I thought one of the more inexpensive fixes would be an ignition tune-up. After looking under the hood, however, I noticed that there aren't standard ignition wires coming from a distributor cap; there is a one-piece coil with 6 rubber boots that attach to the plugs. The service manual says these boots are not replaceable, but they appear readily available online.

Is is it possible (or worth it?) to replace just the plugs and rubber boots on the coil pack. I'm reluctant to replace the whole coil since it's over $100, which is much more than I was planning to spend on a tune up.

Any advice is appreciated.

Thanks,
Andrew

tjwalker

What is your gas mileage? The mileage for yours should be somewhere between 16-21, give or take a bit depending on efficiency, weather, fuel, and how it is driven. You will get less mileage in the winter months.

Be sure to do the math when calculating gas mileage. Miles driven divided by gallons consumed. Trying to extrapolate gas mileage by the miles driven per tank of gas is not particularly accurate.

Get at LEAST 3 samples of your gas mileage before making any assumptions. Poor mileage on a single calculation means very little to accurate analysis.

The coil pack is generally not replaced unless symptoms point directly to it.

For what you describe, (gas mileage) I would not recommend replacing it.

There isn't much more to a tuneup for an 00-01 than fresh spark plugs and air filter.

The NGK is a very good choice for the distributorless ignition that you have. Be sure it is gapped to .035

Oxygen sensors can get lazy over time (and not set a check engine light) and when they do, that doesn't help in optimizing the fuel/air ratio.

grantman18

Wow, thanks a lot for all of the info/advice. I just got my xj a couple of weeks ago, and have gone through 2 tanks of gas. The first one averaged 12.5 mpg (calculated). Granted, it is winter, and I was in 4wd for a few miles, but that still seems low for a 50/50 city/highway split. My last tank was 90% highway and still only got 14 mpg (also calculated) so I thought something might be up. I was going to change the plugs/wires because I don't know about the truck's maintenance history, but didn't realize the engine had a distributorless igintion, so I'll probably just do the plugs and air filter. Any idea what P/N the filter is?

While fiddling with fuses last weekend, my car threw a CEL for a couple of hours after I accidentally disconnected the instrument cluster. The codes (P0130 and P0136) indicated issues with both O2 sensors. Since the light didn't last long I didn't think much of it. Should I replace the O2 sensors to be safe? Just one, or both?

Sorry about all of the questions, I'm pretty handy, but new to Jeep maintenance and want to make sure it lasts as long as possible. Thanks in advance

tjwalker

Oxygen sensors have a "finite lifespan" of between 100k - 150k. If you are in this area of mileage or past it and because of your oxygen sensor codes, (sensor marginal?) I'd consider replacing them. When I go in and replace one, I usually replace both if I plan on keeping the vehicle. Failure of the other one is likely not far behind and the part isn't that expensive. But the upstream (pre-cat) one is the one that affects the fuel air ratio the most.

New plugs, new air filter and see where you are at. Any parts store will be able to fix you up there. Don't use Bosch plugs. Some have had mysterious misfires using them. I'd go NGK. Autolite and Champion are okay too for the 00-01, but NGK is the OEM plug.

4X4XJ

I've got an 01 XJ Limited and I did the same thing. I replaced the spark plugs, coils, and air filter immediately - I used the autolite plugs gapped to 0.35 (a spark plug is a spark plug there is no "better quality" for a Jeep...).

Also FLUSH YOUR COOLING SYSTEM. Change your oil with a good filter. Check transmission fluid and only change it if looks dirty or is not a good red color. Also, check for a valve gasket oil leak (very common) and see if the left side of your engine "looks wet".

Good luck!