A few weeks back, just before Christmas, my son was complaining that my old Grand Cherokee that I gave to him was running like garbage and eating through gas like crazy. We decided to take a closer look...
The check engine lamp was on, so I decided to check codes. When I checked the codes and came up with multiple misfire codes P0300 etc. and an oxygen sensor code P0171. I initially started chasing the obvious suspects such as spark plugs, sensors and fuel injectors to no avail. While, I did get it to run slightly better, it still idled like junk and was setting misfire codes.
Eventually, I decided to perform a power balance by disconnecting the injector leads while monitoring RPMs with my ear. My ear basically told me that I wasn't really losing much RPM when 3 & 4 fuel injectors were disconnected. After I proceeded to swap around injectors to no avail, I decided to do a compression test (I know - this should have been the first thing I did, not the last).
I really didn't think I was going to find anything as while the engine is high mileage (203K), I had always kept up with oil changes etc. . This being the case, I was somewhat shocked to find cylinders 3 and 4 running around 60 PSI. In order to further determine the cause of the low compression, I then added a little transmission fluid to cylinder 3. When I performed the next test my compression didn't seem to change much, however I did experience atomized transmission fluid coming from the cylinder 4 spark plug hole. Looks like I probably have a bad head gasket...
This morning I confirmed my suspicion. When I pulled the head, sure enough there was a gap in the gasket between 3 & 4 (see pics).
Anyway, as long as I'm tearing into the engine I'm taking this opportunity to do a semi/(half-a$$?)-rebuild on the engine. I'm going to clean the head, lap the valves, and install new stem seals. More importantly, I'm going to install new pistons, rings, rod bearings and lifters. I'm replacing the pistons because it's had fairly substantial piston slap over the last couple of years. I quiets down fairly well when warm, but the sound has always disturbed me... so, we're putting in new pistons.
This brings up a question. I'm thinking I'll simply just install new pistons without bothering with honing the bores. My thoughts are:
1. There is no way I want to pull the whole block.
2. I'm afraid if I hone the bores with the crank installed, I'll contaminate the crank and bearings.
3. I'm not too sure I can get a hone into the rear cylinders anyway.
4. My cylinder bores look to be in real good shape.
5. It is my teenage son's car. It doesn't have to last forever maybe a couple more years of local driving.
So, should I hone it? Is this a fatal mistake if I don't? Let me know what you think...