I have a 1995 civic manual 5 speed. It has had a misfire ever since I have owned the car. I have done a full tune up which helped a little but is still there. It had a head gasket leaking which blew and was replaced Saturday. Car runs nearly perfect but I still can detect a slight misfire and it is driving me nuts so I did a compression test with these results: (left to right)
195
195
150
180
Would a 45psi difference in compression cause my misfire? It is still above the minimum 135psi but more than the allowable difference of 28psi. And would a can of 4 cylinder engine restore fix the compression or does that stuff not work as advertised?

 

Bump.

 

Yes.

A leaky vacuum hoses, a busted exhaust valve or a blown head gasket. When two adjacent cylinders are misfiring, chances are that the gasket between them is cracked or damaged.

 

It isn't a blown head gasket because I just replaced it, and if the head gasket was leaking between cylinders wouldn't there be no compression in either cylinder? Also valves looked good when head was off for head gasket replacement. And how many vacuum lines are on my 95 d15b7? The misfire isn't noticeable unless you are looking for it or by the exhaust. It isn't bad at all. I just was wondering , would the 45 psi difference in compressions cause this even though the lowest compression is still 15 psi above the minimum compression requirement?

 

Oh, and the misfire is only at idle, and sometimes my engine would rev up and down during idle. Possibly a connection?

 

Wait... The idle going up and down is from the coolant being low and messing with the FITV (fast idle thermal valve). That is irrelevant. So that leaves us with the slight miss at idle.

 

Bump.

 

Have you checked the valve adjustment?

You can also repeat the compression test-- try putting a little oil in the low cylinder and if that makes the compression come up it's because the rings are worn. Not much you can do about that but it's not going to hurt much until it starts to burn a lot of oil.