Tune up on '04 TJ

[David Jackman]

I would like to give my new to us '04 TJ with 4.0 inline six a tune up. It has 66k miles, and I don't know if it has ever been tuned up. I'm thinking plugs and wires & maybe a new cap.

Should I get OEM parts from Jeep, or what NAPA has to offer?

Your input is appreciated.

Chief

 

[RedTJ]

There isn't much to tune up. If you don't know if the fluids have been changed or not, that's a good place to start. Cooling systems are often neglected. If it's an automatic, fluid changes are often neglected as well. It does not have a cap, rotor or wires. It has a coil rail that bolts onto the block on top of the plugs. Pull that off, and the plugs are right there. Don't use anything weird for spark plugs. It prefers stock style spark plugs. The air filter is easy to inspect and cheap to replace. I'd check it as well. Also, look closely at the rubber and plastic lines and boots for vacuum and emissions stuff. They get old and crack, causing leaks and given the age of your Jeep, it is very likely that there are some cracked rubber boots. Parts stores sell all of that stuff.

 

[Jerry Bransford]

There is no distributor cap or ignition wiring on your '04 TJ 4.0L engine, all you need are fresh plugs David.

Be aware that newer engines like yours (without distributors) are very fussy about their plugs... you can't install just any platinum plug for example.

There are three long-lasting great performing spark plugs I've been recommending for the newer 4.0L for years.

These two will perform well for 100k miles, both are "dual-tipped" platinum plugs. Dual-tipped just means the platinum coating is on both sides of the gap, it doesn't mean it has two electrodes.
1) Autolite APP985 (not AP985!)
2) Champion 7034 (not 3034!)

This is my #1 favorite, it is iridium tipped and will perform well for at least 200k miles.
- Autolite XP985

Any of those plugs would be great choices. Just make sure not to install single-tipped platinum plugs like the Autolite AP985 or Champion 3034, they will cause idle problems and misfires that are extremely difficult to track down.

 

[Jerry Bransford]

It prefers stock style spark plugs.

Not true, the newer distributorless 4.0L engine has no more preference for stock style spark plugs than it does the correct type of double-tipped platinum or iridium spark plugs that perform just as well (usually better) but have 3-5X the life. Newer 4.0L engines are just fussier in that they won't run well on the wrong plugs like single-tipped platinums. That's where some got the mistaken belief it only runs well on stock plugs.

Benefits of the newer plugs like the Autolite APP985 and XP985 include not only much longer life that maintains its same level of performance throughout that life, but also the "fine-wire" electrode technology they use will fire more reliably in difficult combustion conditions. Like a fouled combustion chamber from some kind of an engine problem.

There's no reason to be afraid to use better technology plugs, you just have to know what plugs not to run. And some store spark plug guides definitely give bad/incorrect spark plug information. I've seen some that listed the single-tipped platinum (the wrong technology to use in newer 4.0L engines) Champion 3034 and Autolite AP985 as being appropriate for newer distributorless 4.0L engines but that's incorrect, those plugs are incompatible and eventually will cause a rough idle and misfires.

 

[RedTJ]

Does all this translate to a better running vehicle?

 

[Jerry Bransford]

Does all this translate to a better running vehicle?

Sometimes. Platinum or iridium spark plugs can't/won't cause an engine to run better, produce more power, etc. when compared to how it runs on conventional spark plugs that are the right model spark plug that is in good condition.

What better plugs like platinum & iridium tipped spark plugs do is perform well for 3-4X longer, and they will fire more reliably in difficult firing conditions like a fouled combustion chamber.

Gimmick-science spark plugs like E2's, Pulstars, etc. base their performance boost claims on comparing them to worn out spark plugs. They're definitely not worth buying, no one should fall for their misleading performance boost claims.