What are the best spark plugs for my Jeep Wrangler TJ 4.0?

mots said:
Doesn't look bad at all from what I can tell...hard to see inside the male part of the connector to see what is in there. Do you see any rust or corrosion? If it doesn't help by cleaning out the connector, at least you gave the easy stuff a try first! The one code you were getting suggested a problem with the injector circuit.

I have been wondering what the typical longevity of injectors on a TJ is. It may differ by year. I'm sure mine are still original at 103k and at 13 years old. I don't have any issues, but have been wondering when I might expect to have issues due to typical age and mileage. It also depends on other factors as well, such as the type of fuel used over the course of it's life. While all fuels have a minimum amount of detergent required these days, some fuels have more\different detergents added and have differing amounts of ethanol blended in.
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So let me run this by you and Jerry if he reads it....was talking to a guy today about my misfire situation and he brought up the possibility of a cracked head...does that sound plausible to you guys? Of course I’m almost clueless is this department so anything sounds about right...right about now. It does do a ticking when I crank it up like I read TJs will do when the lifts need to be replaced and the guy today mentioned replacing those when I replace my head gaskets. Whatcha think?
 
mots said:
Doesn't look bad at all from what I can tell...hard to see inside the male part of the connector to see what is in there. Do you see any rust or corrosion? If it doesn't help by cleaning out the connector, at least you gave the easy stuff a try first! The one code you were getting suggested a problem with the injector circuit.

I have been wondering what the typical longevity of injectors on a TJ is. It may differ by year. I'm sure mine are still original at 103k and at 13 years old. I don't have any issues, but have been wondering when I might expect to have issues due to typical age and mileage. It also depends on other factors as well, such as the type of fuel used over the course of it's life. While all fuels have a minimum amount of detergent required these days, some fuels have more\different detergents added and have differing amounts of ethanol blended in.
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Also do you think using seafoam could help my issue considering all that I’ve done and checked to this point?
 
Did you already change out the injector then? If not, I’d be inclined to trust the CEL code you are throwing after clearing the codes and replicating the issue. If it still is also throwing the injector circuit code as discussed, along with misfire code, then I’d focus on that injector before worrying about anything else. If you have done all the other things recommended, and finally replacing the injector fixes the injector circuit code, but the misfire code and your issue still remains, then have a mechanic perform a compression test to check the health of the engine.

Seafoam won’t fix an injector circuit malfunction issue...so make sure you listen to what the codes are telling you. That would be a last resort.
 
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mots said:
Did you already change out the injector then? If not, I’d be inclined to trust the CEL code you are throwing after clearing the codes and replicating the issue. If it still is also throwing the injector circuit code as discussed, along with misfire code, then I’d focus on that injector before worrying about anything else. If you have done all the other things recommended, and finally replacing the injector fixes the injector circuit code, but the misfire code and your issue still remains, then have a mechanic perform a compression test to check the health of the engine.

Seafoam won’t fix an injector circuit malfunction issue...so make sure you listen to what the codes are telling you. That would be a last resort.
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Haven’t ordered the new injector but I will in about 20 minutes when I finish giving this baby a bottle. I also ran this over on a Facebook TJ group page and a lot of guys are saying to replace my crank position censor also.
 
Cal said:
Haven’t ordered the new injector but I will in about 20 minutes when I finish giving this baby a bottle. I also ran this over on a Facebook TJ group page and a lot of guys are saying to replace my crank position censor also.
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Let us know how you make out in the end...we are kind of derailing this thread from what it was intended, LOL (sorry guys!). To me, it seems like the CPS would cause issues in the other 5 cylinders besides just cylinder #3, and you would likely see some sort of CPS related OBDII codes when you scan (if the CPS was the problem). What are the theories as to why it is only happening in cylinder #3 and how would it relate to the Injector circuit malfunction for #3? Doesn't make sense to me. My advice is to stay the course of what the PCM is telling you. Clear the codes (get a cheap device that can read and clear) and try correct what the codes tell you, for the ones that keep coming back before replacing anything else. If you keep getting the "P0203 - Injector Circuit Malfunction - Cylinder 3", then this is very likely the cause for the very specific Cylinder #3 misfire that you initially reported. If you have seen different additional codes since then, or if one of the initial codes has gone away and not come back after what you have done so far, then that will be valuable information as you troubleshoot further. Stay the course and you will get her fixed up!
 
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mots said:
Let us know how you make out in the end...we are kind of derailing this thread from what it was intended, LOL (sorry guys!). To me, it seems like the CPS would cause issues in the other 5 cylinders besides just cylinder #3, and you would likely see some sort of CPS related OBDII codes when you scan (if the CPS was the problem). What are the theories as to why it is only happening in cylinder #3 and how would it relate to the Injector circuit malfunction for #3? Doesn't make sense to me. My advice is to stay the course of what the PCM is telling you. Clear the codes (get a cheap device that can read and clear) and try correct what the codes tell you, for the ones that keep coming back before replacing anything else. If you keep getting the "P0203 - Injector Circuit Malfunction - Cylinder 3", then this is very likely the cause for the very specific Cylinder #3 misfire that you initially reported. If you have seen different additional codes since then, or if one of the initial codes has gone away and not come back after what you have done so far, then that will be valuable information as you troubleshoot further. Stay the course and you will get her fixed up!
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Switched out the #3 injector this weekend and the Jeep is running smooth now! I’ve drove it several times and every time I stop for 10-60min and get back in it to see if it’s going to start the idling like it’s been doing and it just cranks right up and drives smooth. Fingers crossed it just continues and I didn’t jinx it. Haha.
 
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Cal said:
Switched out the #3 injector this weekend and the Jeep is running smooth now! I’ve drove it several times and every time I stop for 10-60min and get back in it to see if it’s going to start the idling like it’s been doing and it just cranks right up and drives smooth. Fingers crossed it just continues and I didn’t jinx it. Haha.
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That’s great, good work!
 
My Jeep always has the p0138 code due to having the upper cats gutted. A while back i was having power issues and found one of the cats was clogged so cheap fix I gutted the uppers. It’s been driving 100% fine since then. I just replaced the spark plugs because I figured it was time. My Jeep has 125k miles so not too crazy for a 4.0.
 
BRaguse said:
@
Jerry Bransford

What about the Champion Iridium # 9034, would you recommend them. I have a 2006 65th Anniversary Edition.
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I'm sure Jerry will chime in. If the 7034 Champions are good (double platinum), then the 9034 should be even better for longevity since the center electrode tip material is Iridium (the ground electrode is is still platinum just like the Autolite XP985's).
 
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Thought I'd share a photo of my double platinum APP985's after 110,000 miles and were never taken out and re-gapped on my 2002 Wrangler 4.0. After all, it was this post that convinced me to buy new iridium XP985'S.
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The top one, cylinder #6 has a .08 gap! Also notice #3, had a bad injector. And it was still running good, no codes, till the injector failed and threw a p0203 and p0303. Running great now with a new Mopar injector and new iridium XP985's. Definitely put some anti size on those new XP985's as they will probably be in there for a very long time.
 
The primary benefit of platinum and iridium plugs is longevity rather than performance. Fuel mileage won't increase any appreciable degree. Neither will horsepower. They can, however, remain out of sight and out of mind for a very long time.

One of my vehicles is a 2005 model that calls for platinum plugs and a 105,000 mile change interval. Later model years of the same vehicle with the same engine call for iridium plugs and the same 105,000 change interval. Although there is no question in my mind that platinum and iridium plugs have a very long service life and are a definite benefit in a modern low maintenance engine, I am hesitant to leave plugs in that long in a jeep I-6 that sees severe use and has a less efficient design evolved from tractor motors.

For later TJ's the manufacturer specifies NGK ZFR5N plugs with a 30,000 mile change interval. Since I drive my jeep about 7,500 miles each year that works out to replacing plugs every four years. This doe not seem too frequent a chore for me, especially because I would have fresh plugs every four years and know that the gap is correct rather than only once every 14 years/105,000 miles by using platinum/iridium plugs for their intended service life.

The factory specified NGK ZFR5N and platinum/iridium plugs cost about the same per mile (using a realistic 105,000 miles rather than some pie in the sky number like 200,000 which has been bandied about by one prolific poster on the jeep forums without any credible substantiation). This leads to the conclusion that double platinum/iridium plugs are great for TJ owners who hate to work on their engines and/or who can't or won't check plugs at 30,000 miles (or ever), but are of no particular advantage for those who like to spend time under the hood and keep tabs on the condition of wear parts such as spark plugs.

NGK ZFR5N, Autolite APP985/XP985 and Champion 7034/9034 are all good plugs. All will work well in a later model TJ I-6 engine. Choose the one that best fits your style of maintenance and comfort level with extended service intervals.
 
I just replaced what appeared to be the original plugs in my ‘06 TJ today, one old plug was gapped at .055 and the rest were between .065 and .075. I replaced them with the Champion 7034 plugs. Oh yeah, about 65,000 miles on the Jeep
 
So the question still stands. What are the best (or most cost effective) plug wires for a TJ? I need to replace the ones in my 98 and am waiting for the combined wisdom of this group before proceeding. :)
 
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SgtMajor138 said:
So the question still stands. What are the best (or most cost effective) plug wires for a TJ? I need to replace the ones in my 98 and am waiting for the combined wisdom of this group before proceeding. :)
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Might want to post this in a new thread, it will get more attention that way :)
 
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Here's the deal. Jerry's Thread is spot on regarding which plugs to use, pre and post 2000. I switched over to the Iridium Plugs, (at Jerry's suggestion) a while back. I had been running Bosh dual tip Platinums for roughly 75k without an issue. The Iridium's are just BETTER ALL AROUND. The 4.0 DIS ignition works well with them, (no issues starting or driving). Gas mileage as some have pointed out will not increase. But that's fine, I'm not Jeep'in for gas mileage. I went with the Autolite XP985s. Can't say how others will do. But the Autolites are working just fine. Price for the Iridium plugs is more than any other. But it's worth it, for a few bucks more per plug to get something that'll go at least 100k, but possibly even 150k or 200k. I think if I get 150k I'll be real happy.

Good Luck and if your thinking to replace your spark plugs in your TJ, don't hesitate to get the Autolite XP985's.
 
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SgtMajor138 said:
My apologies! I certainly was not trying to hi-jack the thread in any way. Someone asked in an earlier post about plugs and wires (like peanut butter and Jelly; they sort of go together).
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Oh no, I didn't intend to come across as rude. I just meant to say that you'd probably get more attention in a new thread. Sometimes questions can get lost in these long posts :)

Admittedly I don't know the answer either, as I have coilpacks on mine.
 
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