random compression readings on one cylinder

[eli96talon]

I was wondering if anyone can explain why I keep geting strange compression readings on cylinder 3.sometimes its at 90 then at 120 then at 145 then 130.the compression goes up and down any way it wants. Also its not the tester,when i comp. Test the other cylinders they always read 185,184,185 it never changes.can anyone tell me why this is happening?

 

[Twinturbo120]

Have you tried doing a "wet" compression test to see what happens?

 

[bryanwheat]

You probably have a bunch or carbon on the valves and combustion chambers. When the reading is low there is likely a piece of carbon between the seat and valve, when it burns out the compression goes higher. Either that or you have a junk compression tester.

 

[spic21]

You probably have a bunch or carbon on the valves and combustion chambers. When the reading is low there is likely a piece of carbon between the seat and valve, when it burns out the compression goes higher. Either that or you have a junk compression tester.

if this is the case try so sea foam, ive seen it work miracles with build ups.

 

[BogusSVO]

Run a leak down test.

You may have an excessivly worn guide in the head that allows the valve to seat at a cocked angle

 

[eli96talon]

The head is 2 weeks old all the componants are new,the headgasket is also new..there is no carbon build up on the valves.I also did a wet test to see if the compression would go up and it didn't.its just strange on day the compression is low and misfiring then 2 hours later its high,then low,then high.

 

[92AWDHX40]

Sounds like something is still wrong, maybe there was a problem with the guides in the head, i learned never to assume things. Head may be fairly new but, you could have a problem in there, regardless.

 

[eli96talon]

Im puting in am order to s.I.m for a fresh block since I don't have any trust in this motor.also I have issues that when under boost the #3 piston pushes the spark plug gap closed shut