1999 ford ranger xlt 4.0 help!

[keiths_sadford]

hi.
i just had my truck in the shop for it miss fireing
its been maybe 3 days since i got it back and the check engine light came back on and its starting to miss again.
when i start it cold it idles very rough until it starts to warm up and it missed a few times when on the high way.
when it was in the shop they replaced a vacume solinoid i think and had to replace the #4 spark plug. im not sure what is causeing it to start doing it again after they fixed all that.
its a v6 4.0
any help would be great. im takeing it back to the shop after work and want some ideas to bounce of my mechanic.

 

[rwenzing]

I'm assuming that the trouble code stored was P0304 for a cylinder #4 misfire. See if you can verify that code.

A #4 misfire often means a small coolant leak into the #4 runner because of a bad head-to-intake gasket. This is common in Ranger 4.0 OHV's. These engines are also known for cracking cylinder heads but that's less common than a gasket leak.