'94 Cherokee 4.0L Tune-up tips requested by semi-newbie

Geez! What passes for a tune up these days. No points, no carb adjustments, not to mention a valve adjustment.

But sence you mention it, you probably will not want to tackle the fuel filter, and unless you are having trouble I wouldn't. But I WOULD do the AIR filter and Rotor while I was at it.

You will naturally get differing opinions on brands. I prefer Bosh platinum plugs, Mopar® wires, cap and rotor. Fram is fine for air filters.

Regards,

DAve

A trick I use ... if it ain't broke, why fix it (does not apply to preventive maintenance items ... fluids, filters, worn tires, worn wiper blades, worn rotors, worn brake pads, ashtray overflowing with loose change, backseat overflowing with ... well ... overflowing ... ). In other words, if you check the plugs, high tension wires, distributor cap and they are good, why replace them?

I second Bowgus' opinion.... if it works, don't fix it. I will go a step further, and advise you to stay away from Bosch platinum plugs. They will take a perfect-running engine and make it run like crap. Not just my opinion, it has been proven over and over again in my service bay, as I toss them into the trash and replace them with 79 cent Champions.

Jerry

Agreed. A Bosch spark plug is the most overrated POS on the market. I see a lot of bad Bosch aftermarket O2 sensors too. Worst part is they don't just quit working, but spew false feedback instead.

Thanks so much for the input, guys. I should add that it is somewhat harder to start than a few months ago and it is idleing a tiny bit rough until warmed up. I'm hoping it's just plugs or whatnot. The other stuff will be replaced if it looks like it needs it. My GF thinks it has had a tune up in the last 3 years (the time that she has had it), but it isn't clear what was done and when it was done. I'm just trying to do my boyfriendly duty and take care of some simple things so the local garage doesn't get her hard earned $$$.

I also subscribe to the don't fix until broken theory. When I replaced the water pump, the heater manifold and several hoses bit the dust just by moving them around a bit. Not to mention the snapped bolt on the block when we decided to replace the thermostat "because we we already there."

BTW, where is the fuel filter? I won't be able to look at the truck until late this weekend and I don't recall seeing it when I replaced the water pump.

Hiya Mike ... I would not put much thought/effort into the idling a bit rough until warmed up ... could be a lotta reasons (like maybe a sensor ... there are a few of them to get to know), I don't believe plugs is one of them. I'd just wait it out and do some reading up on the jeep ... get to know what makes it tick (suggest the Haynes Manual, not expensive, not comparable to a shop manual but covers the basics for understanding). My jeep idled what seemed rough to me when I first got it ... geez ... there are some loose bits in CAT that rattle pretty loud ... passed the clean air check though ... I'll fix it up when the weather warms up. And from your most current post I understand much better where you're coming from ... you're being helpful for the GF.

If it helps, the fuel filter on my '96 is at the rear, close to the fuel pump.

If the air filter has oil in the area where the crankcase vent connects the vent gromment needs to be replaced. Blow back is fairly common the 4.0L engines

My $.02, Jim