3.5 Compression Test Results = Issues
 

As some of you know, I recently picked up another 5th gen. 5.5 to be exact.
The car ran like crap, to keep things short, so I started investgating farther today. I know the front bank spark plugs are bad, today I found the rear to be not too bad, but I'll be replcng all 6 of course.
I am admittedly a NEWB with this level of engine work, so please be patient with my questions. I do have a pretty good theoretical knowledge, but I haven't dug into engines practically yet, other than a 5 man 3406 (diesel) rebuild in school, different ball of wax though.

I've copied this over from the 5th gen forum, as I'm looking for experienced engine advice, I thought this would be a good place to drop it as well. Sorry for the double post. :D

Down to the main issue, Compression. :bawling:

FYI, FSM reads the following:
Standard Compression = 185 PSI
Minimum Compresion = 142 PSI
Maximum Difference between cylinders = 14 PSI

My test results (PSI) :

Cyl #2 >>> DRY test (base) = 150 >>>>> Wet = 210***
Cyl #4 >>> DRY test (base) = 165 >>>>> Wet = 235***
Cyl #6 >>> DRY test (base) = 195 >>>>> Wet = 245
Cyl #1 >>> DRY test (base) = 200 >>>>> Wet = 230
Cyl #3 >>> DRY test (base) = 200 >>>>> Wet = 245
Cyl #5 >>> >>>>>>>>>> Wet = 235

Cylinder#5 has oil in the spark plug hole, so I was unable to get a baseline for that cylinder.

Obviously, it seems cylinder #2 and #4 have bad rings, I thought this was strange though, does anyone else feel that way? I find it hard to believe that just 2 cylinders would wear the rings out and the rest are perfectly fine. Especially 2 cylinders that are right next to each other.

When I did the dry tests I assumed I had a bad headgasket, (hoped it was a headgasket anyhow) but the wet tests don't really lie, so I guess I'm asking if you guys think there could be anything else that is wrong, or am I into doing piston rings on #2 and # 4?
I should mention, the spark plugs on #2 and #4 were carboned up BAD, which re-enforces bad rings IMO.

Oh and can we pull the piston from the bottom? Do we need to pull the whole crank to pull one or two pistons, or can I sneak them out of there?

Also, I am assuming that the oil in my # 6 spark plug hole is just from a bad seal on the valve cover? Can these be replaced without replacing the whole cover?

Thanks for any help here boys, I'd love to get this car up to snuff so I can decide what to do with it.


Oh, here's a couple pics of the process, just cause we all like pics so much :)

http://i468.photobucket.com/albums/r...T/100_3885.jpg
http://i468.photobucket.com/albums/r...T/100_3891.jpg
http://i468.photobucket.com/albums/r...T/100_3893.jpg
http://i468.photobucket.com/albums/r...T/100_3898.jpg
http://i468.photobucket.com/albums/r...T/100_3901.jpg
http://i468.photobucket.com/albums/r...T/100_3904.jpg
Ready for bed:
http://i468.photobucket.com/albums/r...T/100_3905.jpg

So far, all compression test I have seen from a 3.5L FWD have shown that the front bank has lower compression (all 3 cylinders). I came to this observation when I did a compression test on my built motor and turned out to be:

200 , 197 , 200
175 , 170 , 170

Bottom row being the front bank, this is on a 8.8:1 compression 3.5.
However, the engine is fine, no oil consumption and oil analysis have returned satisfactory. I blame the FWD intake manifold, there is uneven air distribution between both banks (I have proven this by logging AFR on each bank). Also if you have PCV hooked up, oil will go to the bottom portion of the manifold, which is why you see different color runners on the manifold.

The oil on the coil is most likely from bad seals on the valve cover, id change that soon. I wouldnt worry much about the compression to be honest.

2 & 4 are closest to the precat in the front, no?
Curious if the front precat may have had some blow-back into the exhaust valves compromising those rings.
'All' front cylinders being lower than rear is fine. 2 of his 3 front cylinders having lower compression than the 3rd cylinder is an issue.
Agreed...get with DAVEB and get some 6th gen valve covers to fix that issue.

We can rule out that its not the precat. I dont have any cats at all and still got this reading, as well as others with same readings and no cats.

Ahh
 

Roarke333 no these cars need fusebox on term and you can get them from nissan relatively cheap