CEL keeps coming back on

[mrblotto]

Greetings everyone,

The CEL keeps coming back on the '01 Jeep Cherokee 4WD. The reader code translates to 'misfire on Cyl 3'. I'll reset it, and it'll come back on in about 2 or 3 days.

My question to you is: Should I just replace the plugs and/or wires first? Or should I do 'the whole magilla' and get a new coilpack as well? The vehicle has about 140K on it. Wires/pack are original. Plugs were replaced maybe 75k ago (by me - the farthest back plug was a pita lol)

Edit: after looking at the coil pack, there appears to be no 'wires' per se lol. Just a short piece connecting the pack to the plug.

Obviously I'm thinking I should check the connections first, but just in case everything is snug.

Thx everyone!

 

[kornphlake]

I'd start by pulling the plugs, if the cyl3 plug looks damaged it's could be just the plug and you don't need new coilpacks. If the plug looks okay replacing the coilpack is a pretty good idea.

 

[bbs lm-r]

Don't wanna sound mean or anything, but it's obviously coming on because it detects a problem, clearing the code isn't gonna make the problem go away.

Checking the plug is a start. Maybe check the gap and see if there's damage to the ceramic part.

 

[Viper GTS]

When this happened on my Mustang (and plugs didn't fix it) I ended up doing a coil pack/injector pair. The parts weren't particularly expensive, & the hassle of getting it done warranted the shotgun of parts.

Viper GTS

 

[AMCRambler]

Plugs and wires on a Jeep should be relatively inexpensive and you're probably due in the normal maintenance schedule to replace these. Do the coil pack only if this doesn't solve your issue.

 

[slag]

Skip the plugs/wires and just drop in a new engine. Its the ATOT garage way.

Oh, and don't forget to "slap on the turbo".

 

[LTC8K6]

One coil pack serves 2 cylinders, right?

Seem like it's probably the plug.

 

[mrblotto]

Thx for the info AT garage peeps! I'm gonna grab some new plugs tomorrow and hope for the best! *crosses fingers*

I have no idea about how many plugs the coil pack serves. I was just going on what I see here:

linky

 

[LTC8K6]

Yeah, it looks like 3 coils for the 6 cylinders, except they are packaged as one piece. You'd think if one of those coils was bad, you'd see misfires on 2 cylinders.

 

[5150MyU]

Yeah, it looks like 3 coils for the 6 cylinders, except they are packaged as one piece. You'd think if one of those coils was bad, you'd see misfires on 2 cylinders.

You would think so but it is not always so.

 

[hanoverphist]

im still leaning towards wires, not plugs or CPacks. 140k on those wires could have them worn a bit. of course, 75k on the plugs and id probably change those just for GP also.

 

[SparkyJJO]

Yeah, it looks like 3 coils for the 6 cylinders, except they are packaged as one piece. You'd think if one of those coils was bad, you'd see misfires on 2 cylinders.

Not always true. My old car had 3 packs, 6 cylinders, and cylinder 5 kept misfiring. It was the coil. Cylinder 2 that shared the same pack was fine.


Given the age of the wires, I'd replace them all, and check the plug while you're at it. If the plug is bad, just go ahead and replace all of them while you're in there. Pack would be last.

 

[jlee]

Can you swap two coil packs and see if the problem moves?

 

[LTC8K6]

Not always true. My old car had 3 packs, 6 cylinders, and cylinder 5 kept misfiring. It was the coil. Cylinder 2 that shared the same pack was fine.


Given the age of the wires, I'd replace them all, and check the plug while you're at it. If the plug is bad, just go ahead and replace all of them while you're in there. Pack would be last.

I didn't say anything was true.

 

[SparkyJJO]

I didn't say anything was true.

Hm, true.

 

[5150MyU]

Usually on a Mopar sixpac you would have to swap wiring to fire the different coils,where as GM you could just swap coils.Not even worth it-test it like the manual says.
Be cheap and just replace number 3 plug and go from there.

 

[5150MyU]

Motor size? I6 or V8?

 

[mrblotto]

Haven't had a chance to swap out the plugs yet. I went and got them, but when I get home it's dark! *shakes fists*. Plus the other vehicle (Celica) is in the garage getting front and rear brakes after about 100K on them lol.

5150 - it's a I6. There's no 'wires' per se that I can see. Only little boot things going from the CP to the plugs. I hope to get in there soon though to swap them out!

And I dont know if you/I can replace individual coil packs. I kinda thought the link I posted a few up had all the coil packs integrated?

piccy

 

[bruceb]

Start with new plugs (of the correct brand and heat range) and new wires. If the trouble still occurs, then try to swap the coil pack. In most cases, it is simply a plug or wire on it's last legs. Note when you put in spark plugs, a dab of antiseize on the threads is a good idea. Also, be very careful to keep the wrench from hitting the porcelain. All it takes is a very minute hairline crack in the insulator and you will still get a misfire code.

 

[CraigRT]

Interesting looking coil setup..
I would still just start with plugs. Why change something that doesn't need changing? Also I've used aftermarket coils before. More trouble than they are worth. Stick with your factory one until its diagnosed as bad.

 

[JCH13]

At 140k on the wires and 75k on the plugs they both should be changed for regular maintenance.

 

[5150MyU]

One piece unit that contains three individual coils-replaced as a unit.
I would go with what JCH13 says.
You would not think you would lose half a coil, but I have seen it happen and by no means am I saying that is what is wrong.
Compression check couldn't hurt while you have the plugs out.Since you know cylinder number three is misfiring.Use OEM spark plugs.

 

[5150MyU]

As well as what bruceb said.

 

[mrblotto]

Update:
Put new plugs in yesterday (along with some anti-seize goo). Reset the CEL yesterday as well. Drove it a couple times - so far so good!

*crosses fingers*