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

[BlueRidge304]

@Cal TSB=Technical Service Bulletin

Have a look here:

https://wranglertjforum.com/threads...idle-after-restart-following-a-hot-soak.2345/

 

[mots]

Well I looked at your pic above, and I can see the insulation where I placed the arrow here. There was a TSB I read that was causing misfires when/if the insulation wasn’t present. Since you have it, no worries!

Thanks @BlueRidge304

 

[RedrumRH]

I got these Autolite XP985, as recommended by @Jerry Bransford. Work great! Used some anti seize, hand tighten, then about a 1/4 turn.

 

[RedrumRH]

*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.

I am also noticing a little more pep after a week.

 

[Jerry Bransford]

Well I looked at your pic above, and I can see the insulation where I placed the arrow here. There was a TSB I read that was causing misfires when/if the insulation was present. Since you have it, no worries!
View attachment 52973

Thanks @BlueRidge304

The insulation for the TSB actually wraps around the #3 fuel injector.

 

[Cal]

Just got back from AutoZone and it ran a P0203 and P0303 and suggested the most likely solution be to replace the ignition coil and spark plugs so since I replaced the spark plugs I guess the ignition coil is the next step.

 

[mots]

Just got back from AutoZone and it ran a P0203 and P0303 and suggested the most likely solution be to replace the ignition coil and spark plugs so since I replaced the spark plugs I guess the ignition coil is the next step.

Hmmm, not sure I agree with the coil. How many miles are on your Jeep?

My thought process would be:

1) Two codes, both for cylinder #3:
P0203 - Injector Circuit Malfunction - Cylinder 3
P0303 - Cylinder 3 Misfire Detected

Same cylinder shows issues, injector wiring circuit/signal issue in #3, causes misfire on cylinder #3.

2) I think there are 3 coils in the TJ ignition coil unit, and I think the middle coil services both cylinders 3 and 4 (someone correct me if I am wrong). If cylinder 4 has no misfire or circuit malfunction codes, then it probably won't be the coil.

See pic here (coils service two cylinders each):

3) Double check the insulation on cylinder #3 as per the post @BlueRidge304 linked. Make sure it has proper insulation. It is likely hot in AL, so even more so to double check that that sleeve is on there. After reading @Jerry Bransford 's post, it is not just the layer of insulation that my arrow in the pic points to. It is a sleeve that needs to be fitted properly if you don't have one. I have a '05 where this was fixed at the factory (05-06), so I hadn't looked at this issue very closely until now.

4) Double check the fuel injector wiring harness connector for injector 3. It might be loose or there might just be corrosion. Clean up the connector with electrical parts cleaner. Blow dry and use some dielectric grease on the connector when you plug back in.

5) If the misfire persists, injector 3 mail actually be faulty and may need to be replaced. I think you can test resistance of the injector circuit with a multi-meter (show been with a certain Ohm range if the circuit is sound).

 

[Cal]

Hmmm, not sure I agree with the coil. How many miles are on your Jeep?

My thought process would be:

1) Two codes, both for cylinder #3:
P0203 - Injector Circuit Malfunction - Cylinder 3
P0303 - Cylinder 3 Misfire Detected

Same cylinder shows issues, injector wiring circuit/signal issue in #3, causes misfire on cylinder #3.

2) I think there are 3 coils in the TJ ignition coil unit, and I think the middle coil services both cylinders 3 and 4 (someone correct me if I am wrong). If cylinder 4 has no misfire or circuit malfunction codes, then it probably won't be the coil.

See pic here (coils service two cylinders each):
View attachment 53057
3) Double check the insulation on cylinder #3 as per the post @BlueRidge304 linked. Make sure it has proper insulation. It is likely hot in AL, so even more so to double check that that sleeve is on there. After reading @Jerry Bransford 's post, it is not just the layer of insulation that my arrow in the pic points to. It is a sleeve that needs to be fitted properly if you don't have one. I have a '05 where this was fixed at the factory (05-06), so I hadn't looked at this issue very closely until now.

4) Double check the fuel injector wiring harness connector for injector 3. It might be loose or there might just be corrosion. Clean up the connector with electrical parts cleaner. Blow dry and use some dielectric grease on the connector when you plug back in.

5) If the misfire persists, injector 3 mail actually be faulty and may need to be replaced. I think you can test resistance of the injector circuit with a multi-meter (show been with a certain Ohm range if the circuit is sound).

Welp....the coil rail did not fix the issue. Haha but at least that’s new and further narrows down the issue. So I guess the next step is to replace fuel injector #3, right? Wrong? Fuck I’m just ready for this check engine light to go off and it to start running smooth again.

 

[mots]

Welp....the coil rail did not fix the issue. Haha but at least that’s new and further narrows down the issue. So I guess the next step is to replace fuel injector #3, right? Wrong? Fuck I’m just ready for this check engine light to go off and it to start running smooth again.

Did you already do my steps 3 and 4? I would definitely do those steps first before replacing the injector.

 

[Jerry Bransford]

Welp....the coil rail did not fix the issue. Haha but at least that’s new and further narrows down the issue. So I guess the next step is to replace fuel injector #3, right? Wrong? Fuck I’m just ready for this check engine light to go off and it to start running smooth again.

Have you thoroughly read all of the posts in this thread?

 

[mots]

Did you already do my steps 3 and 4? I would definitely do those steps first before replacing the injector.

Have you thoroughly read all of the posts in this thread?

@Cal any updates on working through your problem? I was hopeful on my steps 3 and 4 above to save you from installing an injector.

 

[Cal]

@Cal any updates on working through your problem? I was hopeful on my steps 3 and 4 above to save you from installing an injector.

Yea man thanks for checking in. I got a new heat shield and insulation for injector 3, installed and then drove around for 30 min or so and it drove smooth. I got out at the park and then went to get back in l, cranked it and it started back with the same ole idling hard and check engine light. I’ll sohble check the wiring but it looked fine to me.

 

[mots]

Yea man thanks for checking in. I got a new heat shield and insulation for injector 3, installed and then drove around for 30 min or so and it drove smooth. I got out at the park and then went to get back in l, cranked it and it started back with the same ole idling hard and check engine light. I’ll sohble check the wiring but it looked fine to me.

Ok was hoping that was the issue. Were the codes the same? (very important to check) Sometimes connectors get corroded, so maybe you’ll find something there once disconnecting that injector. If you find corrosion (white gunk), clean with electrical parts cleaner, dry out, and reconnect using some dialectic grease to keep moisture out. Definitely seems like something is shorting out once it gets hot, so if it isn’t a corroded connector to the wiring harness, it could be the injector interval circuit shorting out.

 

[Cal]

Ok was hoping that was the issue. Were the codes the same? (very important to check) Sometimes connectors get corroded, so maybe you’ll find something there once disconnecting that injector. If you find corrosion (white gunk), clean with electrical parts cleaner, dry out, and reconnect using some dialectic grease to keep moisture out. Definitely seems like something is shorting out once it gets hot, so if it isn’t a corroded connector to the wiring harness, it could be the injector interval circuit shorting out.

Yea I was hoping that would solve my problems also but at least I’m taking steps towards figuring it out and making my engine better in the long run with everything I’ve done so far. My wife and I are watching Jack Ryan right now but I’ll check for the white funk before I go to bed. I’ll keep ya posted.

 

[mots]

Yea I was hoping that would solve my problems also but at least I’m taking steps towards figuring it out and making my engine better in the long run with everything I’ve done so far. My wife and I are watching Jack Ryan right now but I’ll check for the white funk before I go to bed. I’ll keep ya posted.

Cool, keep us posted. I gotta check that show out since we have Prime, some friends at work are watching it too. The wife and I are getting ready to continue watching Ozark season 2 in a bit, highly recommend that one if you have Netflix. Enjoy!

 

[Cal]

Cool, keep us posted. I gotta check that show out since we have Prime, some friends at work are watching it too. The wife and I are getting ready to continue watching Ozark season 2 in a bit, highly recommend that one if you have Netflix. Enjoy!

Checked my wires and plug for injector #3 and it’s snug down on it and the wires look pretty clean so I guess the next step is to replace then injector as a whole? I’m pretty close to taking it to the mechanic and letting him fix the issue. I’m just tired of not being able to drive my Jeep. Haha

 

[mots]

Checked my wires and plug for injector #3 and it’s snug down on it and the wires look pretty clean so I guess the next step is to replace then injector as a whole? I’m pretty close to taking it to the mechanic and letting him fix the issue. I’m just tired of not being able to drive my Jeep. Haha

So you actually disconnected the #3 injector harness connector and looked at the pins and sockets? This is where the corrosion would be, inside the connector. Just want to be sure we are on the same page.

 

[Cal]

So you actually disconnected the #3 injector harness connector and looked at the pins and sockets? This is where the corrosion would be, inside the connector. Just want to be sure we are on the same page.

I did not, thanks for clearing that up for me. Here are some pictures I just took...

 

[mots]

I did not, thanks for clearing that up for me. Here are some pictures I just took...

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.

 

[Cal]

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.

Yea the Sahara has 92k miles on it and it’s an 01’. I think my final go at it is to change out the injector and see what that does for me. They are 32 bucks on RockAuto. If that doesn’t fix it then off to the shop it goes.