I just got a 90 Cherokee Laredo 4.0 straight 6 with 34,000 miles. It was an island car and drive very infrequently over the past 22 years. I've been slowly going through it (oil change, cooling system flush, fuel filter change, air filter change). It has a sputter when idling. Any suggestions?

 

How long since basic tune up stuff has been done? Plugs, wires, cap, that sort of stuff?
If it sat a lot, a can of Techron in the tank to clean the injectors might not hurt either.

 

Cap wires and rotor look brand new. I took off the cap to check out the inside, everything looked good. Plugs is my next move. The jeep heads at the parts store said jeeps love NGK so that's what I'll go with.

 

Your parts store guys sound pretty good, lol. Plain old NGK, no need for the fancy stuff is exactly right.

You'll find several write-ups by Cruiser54 and others pertaining to your era jeep. Ground refreshing, C101 (big plug on the firewall) refreshing and so forth. Probably not a bad idea to go through them to get off to a good start.

"island car"? Where did the Jeep live?

 

Well actually NGK are great plugs but Champion are more recommended for any 4.0 pre 1999 and NGK are the recommended for 00-01. If I am wrong I am sorry but I think that is what they come from the factory. What I do know is that I have tried several different plugs and found that Champion has always work best for my Jeep.

 

99 and earlier Cherokees go with the Champions. When in doubt, lift the hood and look at the sticker it will tell you what plugs to use. The recommended replacement schedule is every 30,000 miles.

 

34000 miles? Yes that XJ is done, they were factory rated for 25000mi max. You should sell it to me. Really though Wow! You may have some fouling upon the Idle Air Control, Front Left on your throttle body (Throttle Position Sebsor is on the right). Unplug the connector, unbolt it , clean the cone gently with toothbrush and carb cleaner solvent, don't pull on the cone, reinstall. Add some injector cleaner to the gas also. Well that's a lot of trouble, 34000 mi ??, yes you should definatly sell it to me. Good luck, how about a pic??

 

Your 90 4.0 can handle a Champion RC9YC plug, gapped to 0.035" (0.9mm)

 

No kidding! A 1990 with only 34,000mls. It is far and hard to find. I would would love to find something like that. What ever you do get her running right and you WILL be very happy with it. I was surprised to find my 98 with only 98.000mils on her. I have never regretted buying her.

 

Finish the tune up and if it persists verify good compression. Maybe a slightly restricted injector.

 

Good to know. I was mostly surprised that the parts guys didnt' try to sell the OP whatever quadruple-tipped super iridium $9 spark plug they were trying to move that week, lol. Not often you get a recommendation for a plain-jane plug.

 

The jeep is from Nantucket. I got it at an estate sale for $2000. It was owned by an older gentleman that only came to the island three or four weeks every summer. I did notice while playing around under the hood that removing and reinstalling the CCV hoses seemed to make a difference in the idle. The grommets that go into the valve cover are pretty rotten so I thought about getting a vacuum hose harness and putting that on as well

 

The other thing I know is that I'm very new to this motor and everything. I might be making a mountain out of a molehill, so to speak. I guess I'm trying to get some different ideas. I realize the mileage is uncommonly low, and there is nothing majorly wrong with it so I want to get it as perfect as I can so I can be one of those 250000+ guys I read about on here