cassaraM

I have a 2003 ford ranger 3.0 V6 right now it has codes for # 5 and 6 cylinder misfire and also random misfire. it has All new injectors plugs wires the upper plastic intake manifold has been replaced a long with the gaskets when the motor gets to about 2500 rpm you can hear a sqealing sounds i thought it might have been an intake leak but like i said the intake manifold and the gaskets are new any ideas??

rhandwor

Ohm all the injectors any that are way out of line replace. I've used a small screwdriver with a light bulb in the handle slide the tip along side the wire and check for spark on all cylinders. I've also used an ohm meter and checked the wires it normally runs appx. 1/2 scale.
Take a compression test a bad lifter or valve can cause problems.
Use a can of carb. cleaner and spray along the edges of the intake manifold.
If the engine smooths out you have a leak at this point. Its always possible a gasket is pinched or you have a small crack.
Bad injector wires also cause misfires.