low compression on one cylinder ??

[240sx_brett]

#1 cylinder 110 psi
#2 cylinder 160 psi
#3 cylinder 180 psi
#4 cylinder 160 psi
#5 cylinder 180 psi
#6 cylinder 150 psi

I just bought the car it has 194k miles on it. im actually surprised with the pretty good PSI on most cylinders. the engine was apart when i bought it so i never was able to start it. the previous owner said there was an engine knock. im assuming valve tapping since i see thats common with these. would that be a reason cylinder 1 is so low?

[nissanfreak12]

Bad rings, carbon on valves, low battery, throttle not open all the way, head gasket, hose wasnt seated properly from compression tester, engine was cooler than the other cylinders. I could go on.

Was #1 the first cylinder you tested?
Was the battery full or on a charger when doing it?
Was the engine warm?
Throttle open all the way when testing?

If all the test were done the same way with engine warm , etc, then chances are are its either valve issue or compression ring broken. Try and add a tablespoon of oil in that cylinder and retest. If the compresion goes up dramatically, you have ring issue. If not, possibly valve issue.

You can always do a leak down test and that should give you a better idea whats going on. Its actually a better test to do than a compression test.

[240sx_brett]

i retested today with a fresh charge. i havent put the engine back together to have it warm. i was not testing it with the throttle open.

got different results today

#1 150 psi
#2 160 psi
#3 185 psi
#4 160 psi
#5 185 psi
#6 150 psi

the only concern is the variance between cylinders, i have 2 cylinders that are near perfect and the rest are going down.

so they are in ok range. i read in the fsm 142 is minimal.
i was just doing it to see if it was worth putting back together. if i can get a year of driving out of it without much problems. i dont want to rebuild it. when i have the money i will swap a new engine in but right now i just want to have fun with it for a year.

what is your opinion on the variance between cylinders

[nissanfreak12]

I would not stress about it until you test it with the engine warm. They are pretty good numbers with it being cold though. I would put it back together and run it without an issue.

[240sx_brett]

thank you for the confidence. i will go ahead and start doing that.

i know its going to be a b**** to put back together cause it came with the intjectors intake manifold off and i have bolts all over! but i found the fsm on here so hopefully its not too bad