Spark plugs and tune-up questions

[grabeb]

Bought this 01 Jeep TJ Sport a little over year ago. It's kept me somewhat busy with little things suspension, rear brakes, now power steering pump is slated for swap. She's pretty much bone stock for now as my teen drives it. She has about 125k miles and the only error is a fuel system code, which I'm trying to figure out as time permits.

In any case, I figure I should replace the plugs, but looking for what I should be running. It looks like I have an Autolite XP985 in my Amazon list from a year ago as I never have gotten to this. I also have some NGK V-Power plugs in there. I can't recall why I chose to save both of those and even if they are the best fit. Recommendations?

I've changed air filter, PCV valves, obviously oil, rebuilt almost the entire front suspension system as it had some wobble at 65. I've also noticed I have some Chrysler Combustion Chamber cleaner saved in there was well. Is that also something that I should be doing to this?

 

[Jerry Bransford]

You can't beat the XP985 which easily has an >200k mile life of good performance per tests via electron scanning microscopes. NGK is a good brand but conventional non-platinum/iridium plugs only last half their normal life due to the waste spark ignition system used in newer 4.0 engines that fires the spark plugs twice as often on every stroke instead of just on the combustion stroke.

 

[machoheadgames]

I like to stick to the ones in the owner's manual and just change them when needed.

 

[Jerry Bransford]

I like to stick to the ones in the owner's manual and just change them when needed.

Do you stick with everything the factory installed? Conventional spark plugs only last half as long in newer 4.0 engines due to the waste spark ignition system firing them twice as often. It's proven that better technology plugs like the fine-wire center electrode in better platinum and iridium tipped plugs are better at consistent ignition in difficult combustion situations and they last 4-8X as long on the newer ignition system. But if you want to change your plugs as often as conventional plugs need to be changed with the waste spark ignition system that came out with the coil rail be my guest.

 

[machoheadgames]

Do you stick with everything the factory installed? Conventional spark plugs only last half as long in newer 4.0 engines due to the waste spark ignition system firing them twice as often. It's proven that better technology plugs like the fine-wire center electrode in better platinum and iridium tipped plugs are better at consistent ignition in difficult combustion situations and they last 4-8X as long on the newer ignition system. But if you want to change your plugs as often as conventional plugs need to be changed with the waste spark ignition system that came out with the coil rail be my guest.

Lol, no, I don't stick with everything the factory installed. For spark plugs I do.

All I did was make a recommendation, much like you did. I'm well aware of how long spark plugs can last. I've run the 985s myself. I'd rather just run the stockers at this point and change them when they should be changed. I'm also well aware of how the DIS works and know that they wear out plugs twice as fast. It's still not a difficult or painful job.

 

[AjRagno]

With nearly 400,000 miles between 2 TJs (2001 and 2005) I’ve tried maybe 5-6 types of spark plugs. I’m currently using the OE NGK plugs. They may not last as long as other plugs but they do perform well.

 

[TheBoogieman]

I’m currently using the OE NGK plugs. They may not last as long as other plugs but they do perform well.

Extra HP and MPGs?

 

[AjRagno]

Extra HP and MPGs?

I’ve tried APP985s in both TJs a couple of times. They either set specific cylinder misfire codes or P0300 each time except the most recent. I most recently ran APP985s for about a year. They never set a code but it always felt like a miss at idle.

I considered the XP985s but went back to the NGKs about a month ago. The power is fine, smooth idle and acceptable gas mileage.

 

[Jerry Bransford]

I’ve tried APP985s in both TJs a couple of times. They either set specific cylinder misfire codes or P0300 each time except the most recent. I most recently ran APP985s for about a year. They never set a code but it always felt like a miss at idle.

Those issues are more typical from the AP985. I ran the APP985 for years with never a hiccup.

 

[AjRagno]

Those issues are more typical from the AP985. I ran the APP985 for years with never a hiccup.

Yes, I kept trying the APP985s because so many recommended them. I have, however, run the single platinum AP985s without issue.

Funny thing about these Autolite single vs double platinum plugs is if you check reviews, a lot of people with coil on plug TJs have posted of experiences similar to mine.

It’s so easy to replace plugs on the 4.0L that it can be difficult to resist trying something else but I think I’ll stick with NKG for awhile.

 

[Jerry Bransford]

Yes, I kept trying the APP985s because so many recommended them. I have, however, run the single platinum AP985s without issue.

That's backwards. There's even a TSB warning against the use of single platinum tipped plugs like the AP985 or Champion 3034 which is known to cause misfires and bad idles in newer 4.0 engines with the ignition rail/waste spark ignition system that was introduced in 2001.

Were you applying antiseize to the threads of the APP985 plugs and perhaps not or not as much antiseize to the threads of the AP985?

 

[AjRagno]

That's backwards. There's even a TSB warning against the use of single platinum tipped plugs like the AP985 or Champion 3034 which is known to cause misfires and bad idles in newer 4.0 engines with the ignition rail/waste spark ignition system that was introduced in 2001.

I understand what you’re saying but my experience has been otherwise.

 

[TJonfire]

Lol, no, I don't stick with everything the factory installed. For spark plugs I do.

All I did was make a recommendation, much like you did. I'm well aware of how long spark plugs can last. I've run the 985s myself. I'd rather just run the stockers at this point and change them when they should be changed. I'm also well aware of how the DIS works and know that they wear out plugs twice as fast. It's still not a difficult or painful job.

What is the NKG spark plug number? Is it 3459 ZFR5N?

 

[machoheadgames]

What is the NKG spark plug number? Is it 3459 ZFR5N?

That seems correct. The 2001 service manual says RC12ECC, which in my digging turns up a Champion 438 as the factory plug. The NGK part you list seems to be the appropriate equivalent from NGK.