Ive been haveing check engine light on for awhile that says i have a misfire in cil 4 , ive tried spark plugs and a coil but get same.I did a compression test and i get the following :
cil 1 - 140 , cil -2-120 , cil 3-118, cil 4-50 , goes up to 70 after oil is added to cilinder, cil-5-145, cil 6 - 145. Does any one have any clue as to why the readings are all over the place, and would this be a valve seal or piston ring.Thanks

 

What engine? Either a bent/burnt valve or blown head gasket.

 

Thasnks for the responce, it is a 3.7 lt engine.Im thinking of takeing it to the dealer , for a computer diognostics , 100.00 bucks.Yikes.But want to make sure before I tear it apart.What do you think.

 

Another thing I forgot to mention is that the compression test was done on a cold engine.I was afraid to do it on a warm engine because the heads are aluminum.So I'm aware the readings will be off.Should it be this off though?Thanks

 

Cyl 2 and 3 are tolerable, but #4 sounds like a valve issue. You can pull the valve cover and possibly see a broken valve spring that could also cause the valve not to close. Hard to tell without looking at it myself.

 

I did take the cover off , didnt see anything out of the ordinary.I saw in the manual that for the 3.7 engine you can take off the crank case cover and with a spring compression tool , take of rocker arms to inspect them.I see nothing in the manual abought being able to do anything with the valves at this stage.Can I or will I have to take out the heads?Thanks

 

Along with the valve issue, also a cracked head or blown head gasket would cause compression loss.

 

Thanks for the response, I'm going to try replacing the valve seals with the rope trick.I was reading about that technique , hopefully it will work.If not, im throwing a match in the gas tank.

 

Valve seals stop oil leaks into the cylinder. Will do nothing for a compression issue.

 

You can take a spark plug and remove the porcelain and weld a air hose nipple to it. Pull the valve cover and bump the starter till both valves are closed on that cylinder. Hook up the air hose to the cylinder to check. If air hisses out the exhaust bad exhaust valve. out the throttle body bad intake valve. pull the neighboring plugs out. if out those plug holes bad head gasket. I dont think this is the case though or you would have two low cylinders.Bubble out the radiator when the caps pulled cracked head or bad head gasket. Hope this helps. DD