Zach Harris

I recently bought a 98 cherokee 4.0. I got it cheap because it has some major cosmetic issues and a few mechanical issues. It ran fine until a couple weeks ago when it started to die randomly while the a.c. was running. Shortly after, the distributor went out of time, the oil pressure gauge would randomly drop and spike and it started idling rough. Best I can tell about the rough idle is a seized lifter as one of the rockers on cylinder two is hardly moving. My question is, can a faulty oil pump be the culprit? I'd hate to put that much work into something that's not the root cause. Please help!

gat

I'd be worried about the camshaft since you have an issue with lifting the valves and with the distributor.
You can remove the rods and lifters once the valve cover and rocker arm brackets are removed.
Post photographs of them and keep them all in order.

dzywicki

It's pretty easy to remove and inspect the distributor. The timing is pretty simple on these. s long as the cam timing is correct, the distributor can only go in one way. I would start by removing the valve cover, then you can check the valves or remove the rocker arms altogether to inspect. Once you pull the rocker arms, you can pull the push rods. You have to pull the head to look at the lifters.
You can put the engine at TDC and then remove the distributor for inspection. I have had to replace the distributor on my 99 due to the shaft wearing (at 245k miles). It can be tricky to get back in, but can really only go in one way. I highly doubt that the distributor went out of timing on your Jeep.
I have taken out two oil pumps(a 98 and a 99) and both seemed like new. I replaced the first one and didn't bother with the second one. If your oil pump is worn, you have major problems.

gat

Dzywicki is correct. You can't remove the lifters without removing the head, but you can look at the top of the lifter.

Zach Harris

I kept the rockers and rods in order. When I took the distributor cap off, the rotor was set to fire the number 4 cylinder instead of the number one. I've reset the timing on this once already. My other thought was a camshaft positioning sensor, but I'm not exactly sure if that could cause it to come out of time or not.

gat

I don't see any cracks in the tops of the lifters. Was a rod bent or cracked or anything like that?

Zach Harris

No they all looked like they were in good condition.

gat

Maybe the distributor needs replacing. That could be why the timing was thrown. I'd open the case and look at the chain and gears at this point. It is a bit of labor and one gasket of cost away from a photograph.
Also, how is the condition of the crankshaft pulley? Good solid rubber connection and no play?

Whenever you remove the serpentine is a good time to check all of the pulleys really.

lawsoncl

I think it's just a roll pin that holds the gear in place on the bottom of the distributor. Could that have sheared and allowed the gear to rotate?

Zach Harris

At this point I have replaced the crankshaft position sensor, camshaft sensor, distributor, lifters, water pump (not that it has anything to do with timing), bought a new head to put on as a compression test pointed towards bent valves, and I will be replacing the crank and cam shaft sprockets with the timing chain. I have the parts and hopefully will have the case opened today so I can post some pictures.