Replacing piston ring 5VZ-FE

[DenaliJames]

2002 4Runner 5VZ-FE

Just did timing belt and replaced knock sensors and when I put it back together and fired it up it has a constant miss on cylinder 5. Ruled out the routine stuff and did a compression test to find it has 100 psi. Did some research and found that if you pour some oil in the cylinder and compression goes up than it's the ring. Did that test and it jumped to 175 psi to match the other cylinders. My question is can the piston ring be replaced without having to take the motor out of the truck? If so, is there a good write up on how to do it?

 

[gnob]

not a job you would really even want to attempt over the fender.
head has to come off and oil pain.

 

[aztoyman]

Something unusual/bad happened if only one cylinder has low compression because of piston rings. Chances are that you're not going to fix it by throwing a set of rings on it.

You really need to be able to get a visual on what is going on. That's going to require looking inside with a camera or scope down through the spark plug hole or pulling the head.

You're right that low compression is most likely due to worn or damaged rings when it tests higher with some oil added on a second test. But, If this JUST started since you did the work, I would back track and find out what happened. If it had the miss before at least you have the most likely cause. If the miss just started, I'd do some more investigating. It is possible to have lower compression on one or more cylinders and not have a miss. I drive one.

I'm just saying make sure before you go pulling your engine out or apart. I hope it's not too bad. Good luck.