persistant 306 6 cylinder misfire code

[cobra0357]

Ive been messing with this for over a year. 2001 4.0 6 cylinder misfire detected. I put new plugs new coil and wires on it with no results. I checked engine compression all cylinders were 165 to 170. Engine starts right up when cold. When warm you can hear a miss. The idle rpms stay at 500rpm , they do not drop. With a stethescope I can hear the injectors clicking.
Does anyone know what to try next???

 

[2000StreetRod]

misfire causes

Cylinder misfire is normally caused by ignition, fuel injection and compression problems in that order. Did the old cylinder #6 spark plug look normal when you replaced it? If a new plug runs good at first and then later misfires it could be due to coolant, oil or fuel leakage. Have you tried adding fuel injector cleaner to the fuel tank?

 

[cobra0357]

I could try the injector cleaner again. Tried that before and it didnt work. When I pulled the 6 plug it was a little black.

 

[cobra0357]

Would it be ok to replace the 6 cylinder injector only??? I was thinking about trying this next.

 

[swetrid]

What engine 4.0L OHV or SOHC?

 

[cobra0357]

Its the 4.0 6 cylinder

 

[rickybobby]

it is ok to replace just one injector, the way to be sure which it is bad is to swap 2 injectors and see if the code moves with the injector

 

[cobra0357]

Thats an idea thanks Do you think I can get away with using the old intake gaskets?

 

[cobra0357]

REPLACED UPPER AND LOWER INTAKE GASKETS REPLACED THE number 6 INJECTOR WITH A NEW ONE AND ALL INJECTOR O RINGS. Still get the 6 misfire code 306. Can anybody suggest what to do next???

 

[swetrid]

Its the 4.0 6 cylinder

There are two different 4.0L engines. You didnt answer my question. If it runs ok its a OHV if runs really good its a SOHC. Vin # will also tell you.

 

[rickybobby]

the next step is to test the wiring, and compression. It will be very helpful to know which 4.0 you have

 

[cobra0357]

Its the sohc. The compression ranges from 165 to 170 on all cylinders. The wires were changed plugs changed and the coil replaced.