I've been having some probs with the engine feeling like a cylinder was misfiring. I changed the plugs today.



The plugs are in order 1 - 6. From left to right.



This one is plug 1 & 3, plug 3 is on the right. What would make the plug corrode like it did.

 

Every 30,000 miles your 4.0 is due for plugs, cap, rotor, and wires. The plugs should be Champion Coppers or NGKs. The cap and rotor should have brass, not aluminum contacts.

 

Weak spark perhaps.

When was the last time you watched for a stray spark?

How does the cap and rotor look?

New plug wires might be in order.

 

The plugs are 6 months old and the cap and rotor are just over a year old. The cap and rotor is copper. I've had the Cherokee for 2 years and have put 43000 on it. The plugs are the cheap ones from advance and they do arc a little.

 

What brand of plugs? Good wires or VatoZone etc?

 

The plugs was auto lite copper. I replaced the with champion copper plus.

 

The wires?

 

Not sure. They cost $20.

 

Napa/Belden or NGK. Stay away from VatoZone/O'Reilly's etc.

 

Ok I'll be replacing them very soon.

 

? Or not? I'm constantly getting this stuff out of my fuel. Guess the "additives" attract water. That one plug looks rusty to me. My water pump, chainsaws, generators. Don't get me started. Not really happy.

It burns, makes good weed killer. Maybe Chevron will buy it back. Maybe they could also send someone over to pull start my generator some rainy night.

 

That's a good point - what sort of gas you putting in there?

DFlintstone's Moonshine Special? :P

 

I try to use mainly nonethonol gas. It runs better and I get better mpg.

 

If it was the gas then probably more plugs would be corroded. might be bad seal on that plug or piston rings?

 

I guess if I saw that on my engine I might do a compression test if I had some spare time. Being so uneven just sits funny. Or maybe just check some of those new plugs after a couple tanks.

Also...my 90 had stopped holding fuel pressure. After just minutes it wouldn't spurt when I depressed the valve there on the pressure port.

If I cycled the key/pump a bit, and started it warm it would miss a little and idle funny a little. At least #4 injector was leaking. Replacing the injectors solved all that, now after 1/2 an hr it still spurts.

Guess there is no harm in running some injector cleaner through it now and then anyway.

Then vacuum leaks. Doubt that would do that to #3, but might make the others bright.

That rear manifold bolt has a habit of loosening. On anything like that you NEVER want to tighten only one. It can warp/bend, even crack things. If I found that any that where easy to reach where loose, I'd pull the air cleaner and tighten them all, starting in the middle and working out towards the ends. I'd go over three times, a tad tighter each time. It's a bear of a spot to get a torque wrench on them all. Just don't ape on it. If its firm and not turning, no point in going on to break it, a REAL *****. The rearmost bolt underneath takes a little doing, but it can be done with the right extension. For that very back one by the firewall I use way long extensions (18"), with a swivel at the socket. Anyway, that's a good thing to check on any old Jeep.