# compression probs, 93 sentra..



## rnbd81 (Jan 3, 2005)

I originally posted this is in the "engine models" forum under GA16DE, but this is the more suitable place for it, sorry for the double post, maybe a moderator can delete the other one...

I've got a stock 93 nissan sentra, 220k miles....i bought it off a guy real cheap 'cause it was smoking oil out the exhaust and it had little power at all. Anyways, I had the head rebuilt and I replaced the piston rings. I put it all back together and the car ran for two seconds and died...compression check revealed 115,80,80,105. I added a couple squirts of oil and then the check showed 140, 105, 100,125. According to the haynes manual, the jump in psi by the addition of oil indicates bad rings. Well, the rings are new, and were installed correctly. So my only conclusion is that I did not hone the cylinders correctly, and or long enough, since it was my first time doing that procedure. I only honed about 10 or 15 passes per cylinder, with a 3 stone hone, 220 grit, to get the crosshatch pattern, and the drill was moving very slow. Turns out, the first cylinder, which was the highest compression, was the one that I thought I had messed up with the hone. I had accidentally ran the drill too fast ( i thought) and it was more roughed up than the other three. SOO I am thinking that I needed to hone more.

I took the whole engine apart again, and this time i honed for about 1 minute each cylinder, at a faster rate of speed and up/down movement. I also removed a ridge at the top of each cylinder.

Question 1 - could my lack of honing explain the low compression?

2- the ridge in the cylinders was only on about 35% of the total circumference, and all 4 cylinders had it in the same spot, towards the front of the car...does this mean the piston is cocked at an angle? i.e. digging into one side of the cylinder more than the other?

3 - can bad rod bearing cause this piston wobble effect?

P.S. when i first got the car, before i started working on it, it actually idled very smooth (no rpm jumps) but it had engine noise in the head area, (thats' been rebuilt)...it was only when you pressed the gas that the poor power and response was evident 

Ideas, suggestions, thanks in advance

CONTINUED

i just thought of something other things....

since the car only ran for 2 secs and stopped, this means the rings didn't even have a chance to seat yet right? this doesn't happen instantly

does anyone know if the comp #'s are lower on a fresh engine before the rings seat? and if so, could that mean that my problem was elsewhere? It needs to have at least enough comp to run, even from the beginning, but the haynes manual says that the minimum psi is 164 for this motor, my numbers weren't even close to that. Also i did buy Beck arnley standard rings...do you think that it could be that the rings are just not good quality? Their side clearances and end gaps are close to the max ranges of the haynes manual, but well below serviceable limits. 

another thought along those lines, it was about a week between when i put the block together, to when i installed the head and manifolds, in the meantime the vehicle was outside with bags covering the block and multipurpose automotive grease on the block and cylinder walls to keep from rusting, i wiped off the grease and put acetone on the head to clean it before installing the head gasket, i also wiped off the grease from the cylinders but did not use acetone on them. Could it have been that i just needed to oil the cylinders before i started the car in the first place?


----------

