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Off_Road_Teacher 09-27-2011 08:55 AM

Spark plugs on my 2004 tj 4.0l
What's the best spark plug to use and how do u change them. I haven't seen any wires or anything

wwch99tj 09-27-2011 09:27 AM

Autolite ap985 or app985 the plugs are on passenger side of engine under a rail they don't have wires

dfry 09-27-2011 09:50 AM

The Champion 7034 is also an excellent plug. NGKs are what comes stock, if you care to go that way.

Jerry Bransford 09-27-2011 10:16 AM


Originally Posted by wwch99tj (Post 1607781)
Autolite ap985 or app985 the plugs are on passenger side of engine under a rail they don't have wires

The double-tipped platinum APP985 is a very good choice but not the single-tipped platinum AP-985, make sure not to use the AP-985 in any 2000 or newer 4.0L engine which has the current DIS (distributorless ignition system) system.

Three very good plug choices for 2000 and newer 4.0L engines include the Autolite APP-985, Autolite XP-985 (iridium tipped) or Champion 7034.

1999 and older TJ 4.0L engines with distributors aren't all that fussy about their spark plugs but 2000 and newer certainly are. :)

Wyominer 09-27-2011 10:26 AM

APP 985 (Double "P") not the single "P". I put in XP985 a month or so ago in my 06, no problems. On the right side of the engine remove the "rail" bolts, then gently work the rail up n down until the boots come loose. The rail will stay connected and you will move it around as needed. I change one plug at a time, blasting air down around the plug, loosening the plug, another blast of air (this should remove any crap down around the plug), remove the old plug. You can use canned air if you don't have an air compressor.

Check the gap on all the new plugs, .035 is the proper gap. Put some anti-seize on the threads of the new plug. What I do is use a piece of plastic tubing over the end of the plug to thread it into the hole. This makes it easier to get the plugs started and lessens the chance of cross-threading the new plug in the hole. Tighten the plug down tight, then tighten 1/4 turn. (Get it snug, then 1/4 turn). After all six are changed, put some di-electric grease on the plug tips, re-install the rail. Not being a SA, but make sure all the boots are installed and down tight, rebolt.

You will want to remove the airtube, and have a wobble or "U" joint for your rachet extension, as the front and back plugs can be had to get at.

I changed my plugs in about an hour. My Jeep had 49000+ miles, three of the old plugs had the gap out to .046 and greater. Changing the plugs made a noticable difference in start-up and idle. Good luck!

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