i got 98 civic coupe with ls swap cylinder 1, 2, 4 compression is at around 160- 170 and cylinder 3 is at or below 50 psi, what can cause this low compression and i idles low ans sounds like its gonna die

 

could be a bad head gasket, but most likely either a leaky valve or piston ring.

 

cylinder 3 has shot rings so your getting blow-by..... i would replace them asap before you do more damage

 

ok i was thinking if i have a bad piston ring then i should be burning oil
so it should be the valves right
is this correct or no

 

well a compression test will only show so little i would recommend getting a leak-down test performed on your motor to make sure its rings or not but you can also try this pour a SMALL amount of oil down in cylinder 3 since in your case is the "bad" cylinder if this changes compression it will show you which is bad rings or bent valves

 

tried that oil trick but the compression stay the same
im also getting engine code 71, 73, 74


Modified by zc89hatch at 9:57 AM 8/19/2008

 

ok i got codes 71 72 73 74 which is mis fire in all the cylinders and was wondering if it has anything to do with the 50 psi in cylinder 3 and the rest around 160 and 165

 

maybe your timing belt skipped a tooth?

 

my timimg is good

 

solve my problem. One of my intake valve was crack thats y i was losing compression and thats y it was throwing those engine codes. thanks for all the help

 

Hi,

I may have the same problem as you, Cyl no. 2 compression is very weak 70 to 80 psi compared to the rest 180 - 190. I know its not the rings " did the oil trick" I think it could be either head gasket or a valve may be cracked or burnt.
My question to you is this:
Were you able to change the one valve or did you have to do a complete valve job?

 

theres no reason to change the complete valvetrain because of one valve unless all of them are bent or cracked. just change the valve thats cracked

 

would it be as simple as pulling the bad valve out and placing a new one in its place? or will the head need to be machined for that valve?

thanks

 

found one valve bent and caused deformation in the seat in the head. thankfully is did not cause damage to the piston. I did have to get another head sine the original one could not be re-seated.
Got it all put together purrs like a kitten
Thanks for all your help