Ok just bought a 2001 Cherokee and it’s giving me problems i need some help. It started by running rough when stoped at a light (chugging and puttering) after driving for about ten fifteen minutes. Does not have this problem cold. I installed a heat shield kit by design engineering because i suspected the issue to be heat soak but that did not work. Now my check engine light is on and it’s throwing a Misfire code in cylinder 3. Also when stopped oil pressure drops like a rock. Any input would be greatly appreciated because i have run out of ideas. Also if i let it sit for 15 min it has a hard time idling at all. My fuel rail is rusty but I’m not sure if that would affect it at all.

 

What does the oil pressure drop to? What is it at running RPM? Any engine noise when it's low? You better figure out if that's a gauge/sender problem or a pump/bearing problem fast.

Switch injector 3 with another one and see if the problem follows it.

Got a multimeter?

This is going to be another long thread...

 

Pretty much what Dave51 asked.
13 PSI for oil pressure is acceptable at a very hot idle.
Low end of acceptable, IMO, but acceptable.
Have you pulled the plug on cylinder 3?
I was getting a P0304 about a month ago.
Easiest thing first. Pulled the plug and replaced it despite it looking OK.
No more problems.

 

I’m thinkin the oil pressure is alright but I’m worried about the rough idle i replaced all the spark plugs and the coil but number 3 felt a little loose like somebody stripped it before me maybe bad compression?
also no engine noise when low pressure just the chugging it’s at about 1500 rpms

 

I'm afraid you may have a cracked cylinder head. You might check the condition of your antifreeze and oil. If your engine is factory, you may have the 0331 head which is known to crack between the 3rd & 4th cylinders.

 

Easy check for that is the milkshake test. If it's bad enough you'll see it just by taking off the oil filler cap on the valve cover.

 

OK so why are you thinkin that?

Stripped what? The head? I don't believe that is technically bad compression, I think that's called ****ing up the head.

 

What am i looking for in the milkshake test i replaced the valve cover gasket and saw a foamy white substance but a mechanic friend of mine said it’s moisture because it’s been sitting a while. what does this show cracked head?

 

correction looks yellow green think I’m shot.

 

Two things I would recommend,
1. Change oil and filter. Wix 51085 or NAPA 1085 and refill with Rotella T6 15w40 oil.
2. Pour a can of Seafoam in the gas tank and do that for a couple of tanks.