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

mastergunnera8 said:
ODPA going in, cant find a mopar sensor (discontinued), so its gonna be a Echlin.
Click to expand...
Re-use the MOPAR in the existing OPDA unless there's a specific reason you need to replace it. As for never-seeze - I personally put it on the coil rail bolts, but that's just me. A career in a marine related field has that ingrained, rightly or wrongly. YMMV and all that...
 
  • Like
Reactions: mastergunnera8
Jerry Bransford said:
Either of those gapped to .040 would be fine for your newer TJ.
Click to expand...

Amazon has a note on the Iridium XP-985 "Gap: .035" Amazon also knows I have a 2005 TJ. Having never bought spark plugs from Amazon before I'm curious, is that them telling me what the correct gap is for my vehicle or if that is them saying that the XP-985 comes gapped to .035?
 
Captain Phoenix said:
Amazon has a note on the Iridium XP-985 "Gap: .035" Amazon also knows I have a 2005 TJ. Having never bought spark plugs from Amazon before I'm curious, is that them telling me what the correct gap is for my vehicle or if that is them saying that the XP-985 comes gapped to .035?
Click to expand...
.035 is the specified gap for a lot of engines including our TJ 2.5 and 4.0 engines.
 
  • Like
Reactions: Captain Phoenix
Jerry Bransford said:
Either of those gapped to .040 would be fine for your newer TJ. The iridium XP-985 will just outlast the APP-985 by about 100k miles to get no less than 200k miles or wear.

Make sure to not use a tapered style spark plug gapping tool on iridium or platinum plugs, they'll damage the coating. Use the type with the gapping tool that bends the electrode, like this one has on the left-hand side.

View attachment 223618
Click to expand...
Took your advice here this week Jerry and replaced champion plugs with the App plugs. The only reason I did this was I got a random misfire code. The Jeep was driving great however. Anyway , changed em and desire me believing the everything was great before after changing idles quieter and smoother. So thanks and looking forward to them lasting.

ps the maker advises against adding any anti seize and quotes the material the plugs are made of these days makes this unnecessary
 
LJtheunicorn said:
Just added the xp 985 to my amazon cart for $6.38. Will be tackling these after I take it to the shop and have the rear main seal replaced. Thanks again for all the helpful information on this site!
Click to expand...
Does yours have a slow leak at the rear main seal? What did they charge you? Need to get mine done and wondering price range.
 
Captain Phoenix said:
Mine has what the previous owner thought was a slow leak from the rear main seal but my mechanic thinks it's a valve cover leak that's running down and dripping off the rest of the engine by the rear seal.
Click to expand...
Well that sucks in general. Good luck hope it is a cheap and inexpensive fix.
 
Chief Brohician said:
Does yours have a slow leak at the rear main seal? What did they charge you? Need to get mine done and wondering price range.
Click to expand...
They quoted be around 500 for the rear main. Haven’t done it yet. I switched to high mileage oil and am going to replace the valve cover gasket and see if that fixes it first. Planned to do it a couple weeks back and then texas froze over and haven’t had a chance since.
 
  • Like
Reactions: chrisjohns38, Jerry Bransford and Chief Brohician
I ordered plugs..xp985 for my 4.0 Wrangler. When I found out they were coming ten days later,I tried to canx but they were already shipped. I couldnt wait so I bought the plugs at Advance.. So today they came but they are AP985 not XP985.. Im glad I didnt wait. So now im wondering should I uase the AP985,s in my 2004 Grand Cherokee 4.0?? Or should I send them back? Thx
 
I got mine changed out this weekend on my new to me 2002 TJ.

6A6D20B3-7DEF-4719-80E4-38760178C661.jpeg
 
  • Like
Reactions: Chief Brohician and Chris
xackley said:
A P0301, misfire cylinder 1, could be fuel, air, or spark. Pain to diagnose. Dump a can of SeaFoam or B-12 into a full tank of gas, run it 20 miles and pray.
Let it idle for 15 minutes, pull plug 1 and 2. If 1 is lighter, not enough gas or too much air. If darker or wet, probably missed or weak sparks.
You should also do a compression check even if the Sea Foam cures it. All cylinder readings should be close.
Click to expand...
Misfire might be because of the vapor lock, not ignition if it happens when engine is hot.
 
Fun fact- Our Jeep’s can run on lawnmower spark plugs! (with some small possible misfires)

I recently had my engine replaced and ordered some OEM NGK spark plugs from Amazon and had them drop shipped to my repair shop. Somehow the plugs inside were misboxed or returned. Long story short, my engine ended up with 2 NGK plugs and 4 Champion RC12YC (super common Briggs and Straton lawnmower spark plug). The Jeep ran great for a hundred miles or so then I had a small misfire in cylinder 2. My plan was to replace the plug with a new one and retest thinking I had a failed or contaminated plug. That’s when I found the champion plug in cylinder 2 and a couple others. Replaced all 6 plugs with the OEM NGK plugs. Definitely runs a little smoother now.

If you’re stranded and in need of some spark plugs. Go borrow a few lawnmowers and you’re set!
 
  • Haha
  • Like
Reactions: Chief Brohician and Zorba
Jerry Bransford said:
The later model 4.0 engine (2000 and later) is what is known as a DIS (Distributorless Ignition System) which is far fussier about what spark plugs it likes to run well on.
Click to expand...

Hi Jerry,

Thanks for this. I wonder what the answer would be for the early-model 2.5L engines? Like my 97.

Of course if that has already been answered somewhere in the eight pages of comments, just let me know and I'll go find it.
 
SSTJ said:
Hi Jerry,

Thanks for this. I wonder what the answer would be for the early-model 2.5L engines? Like my 97.
Click to expand...
Yes that was answered but an Autolite AP-985 or Champion 3034 would be good choices that would give something like 100k miles worth of good performance. The iridium-tipped Autolite XP-985 would be good for more like 200k miles. There are other brands like NGK that have equivalent plugs that will work fine too, though I would avoid Bosch in a Jeep engine. For some reason, likely heat range related, Bosch spark plugs don't work well for us.
 
  • Like
Reactions: SSTJ
Jerry Bransford said:
Yes that was answered but an Autolite AP-985 or Champion 3034 would be good choices that would give something like 100k miles worth of good performance. The iridium-tipped Autolite XP-985 would be good for more like 200k miles. There are other brands like NGK that have equivalent plugs that will work fine too, though I would avoid Bosch in a Jeep engine. For some reason, likely heat range related, Bosch spark plugs don't work well for us.
Click to expand...

Great, thanks!
 
  • Like
Reactions: Jerry Bransford
Top Bottom
Back