#6 miss fire

[Eaglefixer]

I have a friend that has a 2000 Ranger XLT 3.0 Auto and is having problems. He has changed coil pack, plugs and wires, #5 &#6 fuel injectors and have cleaned fuel rail and fuel filter. Has ran Gas treatments afew times. The check engine light is intermittent. I'll check codes tomorrow and report the finding. He also tells me that he had the engine compression checked and all cylinders were 110psi except for #6 which was 75psi. I think he may have a burnt valve but would like too hear what you guys think. One more thing is that it runs rough at idle but run fine above that.

 

[necessaryevil]

if it misfires through the intake it is a burnt intake valve, if it misfires though the tail pipe its a burnt exhaust valve, if(when cold)you remove the radiator cap, start it up and the coolant surges its a crack head,or blown head gasket, if you get a lot of air from the dipstick tube when its running means a cracked block,piston, or blown head gasket, the best way to tell is with a leakdown tester. if you dont have one or cant get one then use a piece of brass with the same thread as a spark plug, rotate the engine so the bad cylinder is at TDC then connect an air compressor(set to about 40-50psi)to the brass and run the brass down the spark plug hole. and listen to the intake manifold, exhaust, dip stick tube, and radiator to figure out where you are losing cylinder pressure

 

[Eaglefixer]

Ok, We have no check engine light on but downloaded code p0306. I cleared code and ran truck about 2 minutes and no codes or check engine light. I told him to drive it and if the CEL comes on to let me know. Also told him to have a cylinder leak down check done on #6 as you suggested.

Thanks for the help

Steve

 

[Eaglefixer]

just to update that the CEL is back on and now there is a ticking noise coming from the driver's side of the motor. I downloaded the codes again and it p0306 again. he still haven't done a leak down test yet but looks like he be doing it soon.