Cal
TJ Enthusiast
Post a photo of the passenger side top of your engine so we'll both know what you have ignition system-wise.
What are the best spark plugs for my Jeep Wrangler TJ 4.0?
- Thread starter Jerry Bransford
- Start date
OP
You have an ignition coil rail and no ignition wiring. Just install good spark plugs like the Autolite XP985, Autolite APP985, or Champion 7034. My first choice being the XP985 (iridium tipped) good for 200k miles. The other two are platinum tipped and good for 100k miles. Your particular ignition system is fairly fussy about which spark plugs it will run well on.
Cal
TJ Enthusiast
*Update* on Autolite XP985's (Iridium Plugs)…...so I've had these babies in for about a week now. I driven maybe 100 miles so far. Without a doubt I'm getting slightly better response and better gas mileage. I'd say you'd have to be really "plugged" :thumbup: into your Jeep to actually feel the performance difference.....but it's there, believe me. As for gas mileage, well since it's only been a week and 100 miles, the only real evidence I have to go on is my fuel gauge and how it reads. But I know it well enough to know, it isn't dropping as fast. So I've got to be doing better on mileage.
Bottom line, these plugs are more expensive. But your not going to have to do a change for a long time. I like to check the status of my plugs every 30k to 40k miles anyway. So I'll let you know how their wearing/looking at that point.
The Bosch Plus 2 Plugs I had in there, had a little carbon deposit after many years. But I have to admit, they were not the right plug for this application. Just feeling a performance difference is enough for me to say, "Yeah it's worth it". Spend the money....these plugs are worth it.
Bottom line, these plugs are more expensive. But your not going to have to do a change for a long time. I like to check the status of my plugs every 30k to 40k miles anyway. So I'll let you know how their wearing/looking at that point.
The Bosch Plus 2 Plugs I had in there, had a little carbon deposit after many years. But I have to admit, they were not the right plug for this application. Just feeling a performance difference is enough for me to say, "Yeah it's worth it". Spend the money....these plugs are worth it.
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I installed these plugs last month after having a misfire code and poor idle. My TJ runs great now & no codes!
Wagon Man, if you remember, let us know after you put them in and drive around a little what you think of them. That's a GREAT deal at Autozone!!
i bought the xp985 as recommended here it will be at least a month or two before i swap them out
Cal
TJ Enthusiast
Hey Jerry so my Autolite XP985 Sparkplugs should be in on Monday, any advice on replacing them myself? They come pre-gaped so that’s done and I found a pretty good video on YouTube but I imagine changing plugs is pretty doable for a novice like myself....right? Haha
OP
Cal
TJ Enthusiast
OP
Pretty simple then, just make sure all of the rubber boots get properly seated fully down over the spark plugs. If that sounds like a no-brainer lol, it is but it's not exceptionally hard to miss one. I'm guilty of having one miss the plug without noticing until I started the engine with a very bad miss lol.
Shine a light down inside the boots and make sure all the clips are in good shape and look alike.
Hand thread each spark plug in at least several turns to insure they won't cross-thread. Using a wrench too soon is to invite stripped threads. Use a 3/8" ratchet wrench to tighten them. Use of a 1/2" ratchet greatly increases the chance of overtightening or stripping the threads. Using just one hand on a 3/8" ratchet drive to tighten each plug "real snug" will be fine.
A very small carefully applied dab of common antiseize on the threads kept away from the electrodes wouldn't be a bad idea
Finally, regapping the plugs probably will not be necessary but if you do, you can go to .040 vs. the factory .035 due to your coil rail's slightly hotter spark.
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Cal
TJ Enthusiast
You’re the best Jerry. Thanks a ton.Pretty simple then, just make sure all of the rubber boots get properly seated fully down over the spark plugs. If that sounds like a no-brainer lol, it is but it's not exceptionally hard to miss one. I'm guilty of having one miss the plug without noticing until I started the engine with a very bad miss lol.
Shine a light down inside the boots and make sure all the clips are in good shape and look alike.
Hand thread each spark plug in at least several turns so insure they won't cross-thread. Using a wrench too soon is to invite stripped threads. Use a 3/8" ratchet wrench to tighten them. Use of a 1/2" ratchet greatly increases the chance of overtightening or stripping the threads. Using just one hand on a 3/8" ratchet drive to tighten it "real snug" will be fine.
A very small carefully applied dab of common antiseize on the threads kept away from the electrodes wouldn't be a bad idea
Finally, regapping the plugs probably will not be necessary but if you do, you can go to .040 vs. the factory .035 due to your coil rail's slightly hotter spark.
Cal
TJ Enthusiast
Ok, Jerry, I replaced the spark plugs with success and the Jeep was running great and smooth and now the check engine light has come back on and it’s running really hard again like it’s misfiring. Now it did this a few weeks after I got it and I had the codes ran and they were P0202 and P0203. Do you think it’s the rail causing the misfire or the fuel injectors?Pretty simple then, just make sure all of the rubber boots get properly seated fully down over the spark plugs. If that sounds like a no-brainer lol, it is but it's not exceptionally hard to miss one. I'm guilty of having one miss the plug without noticing until I started the engine with a very bad miss lol.
Shine a light down inside the boots and make sure all the clips are in good shape and look alike.
Hand thread each spark plug in at least several turns to insure they won't cross-thread. Using a wrench too soon is to invite stripped threads. Use a 3/8" ratchet wrench to tighten them. Use of a 1/2" ratchet greatly increases the chance of overtightening or stripping the threads. Using just one hand on a 3/8" ratchet drive to tighten each plug "real snug" will be fine.
A very small carefully applied dab of common antiseize on the threads kept away from the electrodes wouldn't be a bad idea
Finally, regapping the plugs probably will not be necessary but if you do, you can go to .040 vs. the factory .035 due to your coil rail's slightly hotter spark.
OP
Very doubtful it's the spark plugs or coil rail. For two different injector codes that occurred simultaneously, I'd suspect something common to the injectors and of those possibilities, I'd suspect the fuel injector wiring harness. Check the harness near the back of the valve cover where there's a threaded stud sticking up that the harness passes next to. There are a lot of instances where the the fuel injector wiring rubbed through on the threads of that stud and started shorting to ground. No guarantees but that'd be where I'd start looking. Check the connectors too.
Cal
TJ Enthusiast
Now I just gotta decide if I want to drive a rough idling Jeep up to autozone to have the codes ran to make sure it’s the same codes it was before.
Cal
TJ Enthusiast
What’s TSB? I looked at all of the wiring and it all seemed well enough to me (no corrosion or looks of shorting) but what the hell do I know? Haha.