Good afternoon everyone. I am having an issue with my blazer and was hoping to get some advice. 2000 chevy blazer, 4.3L v6 vortec 2WD. I am getting a misfire on cylinder #4. Have spark, checked spider injector and have fuel. The compression is reading 60 psi. There is no oil coating the spark plug. Please help me with the next step?

 

Squirt a small amount of oil in the spark plug hole and repeat the compression test. If it increases significantly, the problem is probably bad rings. If not, it could be leaking valves, bad head gasket, damaged piston, etc.

To do a proper compression test, you should remove all spark plugs, disable the ignition, and hold the throttle wide open while cranking. If you didn't do that, repeat the test that way before doing anything else. That will also give you a reference for the "good" cylinders.

 

Forgive me but I'm not sure I understand completely. I can remove all the spark plugs but if you can elaborate on disabling the ignition? If I disable that how can I turn it over? Are you referring to the disable the injectors?

 

I mean disconnect the coil so you don't have sparks all over the place while you're cranking it. Either pull the coil wire off the distributor and ground it, or pull the 12V wire off the coil.

 

I see. Quick question it it is a blown head gasket wouldn't I smell oil or antifreeze in the exhaust or have milky oil?

 

Only if it's leaking between the cylinder and a coolant or oil passage. Not (for example) if it's blown between cylinders.

 

I just finished the wet test and nothing changed. I did a proper compression test and every cylinder is a 170 psi except for cylinders 4 and 6. They are at 75 psi. I never thought I'd be saying this but please tell me its the head gasket?

 

It kinda sounds like it. You could use compressed air to pressurize one of those cylinders and see if it leaks out the other one.

 

Just put air in both (1 at a time) and nothing happend. Cylinder head replacement?

 

What do you mean by "nothing happened"? Did air leak out somewhere? Did it build pressure at all?