Spark plugs and engine warm ups
- Thread starter RaymondT
- Start date
Nick Honeycutt
New Member
So I recently did my plugs in my 02 tj, put some autolite platinums in and on initial startup after replacing them the jeep sputtered a bit.. is that normal after changing plugs.. first time for everything lol
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I don't know if it's normal, but if it happened once and went away, I wouldn't worry about it at all.
Nick Honeycutt
New Member
Nick Honeycutt
New Member
The AP985 was the wrong choice of plug for your 2002 4.0L engine. So is pretty much any Bosch, they just don't run well in our Jeep engines. A Bosch engineer said it was probably because they don't offer as wide of an assortment of heat ranges with their spark plugs as more mainstream spark plug manufacturers like Autolite, Champion, and NGK do.
The Autolite AP985 was the wrong choice because you have a distributorless 4.0L engine which has a "waste spark" ignition system. What you should have gone with was the Autolite APP985. The AP985 is a "single-tipped" platinum plug which means its platinum coating is only on one side of the gap. That causes misfires with a waste spark system. The APP985 is a dual-tipped which means it has the platinum coating on both sides of the gap which is what your waste-spark ignition requires when running a platinum plug.
And yes I understand some spark plug guides include the AP985 as a compatible plug for your model year. They're just not always correct.
Or you could go with the Autolite XP-985 which is iridium tipped and fine with your ignition system. The iridium gives the plug about 200k miles of good performance, the platinum coating will give about 100k miles of good performance.
So to avoid confusion, I'd go with either the Autolite APP985 or Autolite XP985. I'm running the XP985 myself but the APP985 would be a great choice too.
Next time you can just type the answer I was asking for, that image was confusing to an old guy like me.
The Autolite AP985 was the wrong choice because you have a distributorless 4.0L engine which has a "waste spark" ignition system. What you should have gone with was the Autolite APP985. The AP985 is a "single-tipped" platinum plug which means its platinum coating is only on one side of the gap. That causes misfires with a waste spark system. The APP985 is a dual-tipped which means it has the platinum coating on both sides of the gap which is what your waste-spark ignition requires when running a platinum plug.
And yes I understand some spark plug guides include the AP985 as a compatible plug for your model year. They're just not always correct.
Or you could go with the Autolite XP-985 which is iridium tipped and fine with your ignition system. The iridium gives the plug about 200k miles of good performance, the platinum coating will give about 100k miles of good performance.
So to avoid confusion, I'd go with either the Autolite APP985 or Autolite XP985. I'm running the XP985 myself but the APP985 would be a great choice too.
Next time you can just type the answer I was asking for, that image was confusing to an old guy like me.
Last edited:
Nick Honeycutt
New Member
Sorry.. I should have lol.. so is it ok for now that I did that? Do I waste 20 more bucks and go get a different set?
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The AP985 will eventually start causing misfires and bad idle issues. It's up to you whether you want to replace them with the right APP985 or XP985 plugs. To me, $20 is no big deal when it means my engine will run properly for a longer period of time. I would call the $$$ you spent for the AP985 a waste, I wouldn't call the $20 for the new APP985 or XP985 plugs a waste.
Nick Honeycutt
New Member
Ok really appreciate the input and help!
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PStov98TJ
TJ Enthusiast
While we're discussing plugs, caps, and rotors, would this be a good rotor for the 2.5l? https://www.napaonline.com/en/p/ECHMO31
I've found a store that sells caps with brass contacts. And thank you @Jerry Bransford for the countless recommendations on XP985's as well as finding a source for the OE ignition wiring.
I've found a store that sells caps with brass contacts. And thank you @Jerry Bransford for the countless recommendations on XP985's as well as finding a source for the OE ignition wiring.
If it's brass that looks good. Distributors and rotors with brass contacts are getting hard to find.
PStov98TJ
TJ Enthusiast
You can say that again. Almost everything has aluminum contacts that I've seen. I wasn't sure if it was brass or not. The description doesn't say. Guess I'll have to go down to the store tomorrow and look.
PStov98TJ
TJ Enthusiast
How often is a cap and rotor replacement recommended? I know wires should be replaced around 75k miles, and plugs depend upon which ones are installed.
I need to look closer I saw a video that showed rotor cap as square, they didnt show taking off then someone posted something to the effect that they stopped using a rotor....? Sorry not a mechanic so learning as I go. I did order the autolite xp 985 plugs you recomended so tks!
Older engines used round distributor caps and rotors inside them that spun around to connect the spark voltage to each of the spark plug wires. Newer engines do all that electronically so pretty much all engines now have abandoned the old-school round distributor caps and rotors. The 4.0L engine did away with the round distributor cap around 2000. The 2.4L engine never had a distributor cap. I don't think the 2.5L engine ever got rid of the round distributor cap before being replaced with the 2.4L engine.
PStov98TJ
TJ Enthusiast
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