help 4.0 misses severly

[speedobsession]

i have a 2000 ranger w a 4.0 and recently developed a rough idle. first code was a cylinder#4 misfire. after plugs and wires it was gone until engine warmed up.since then it has developed a rougher idle and upon loading it will loosen fillings.it since has coded misfire on 4 and 6 cylinder #s along with a left bank up stream o2 sensor and a code 1151 manufacture fuel air mixture?in the last two days i have replaced #4 and 6 injectors for the misfire,plugs and wires(quadruple) checked the wire locations. i have replaced the upstream bank 2 o2 sensor again along w the the thermostat and the temp sensor as i then coded a highoutput temp code this is in addition to the intake gasket replaced as well.it drinks gas like no tomorrow and since my final clearing of codes i have not gotten another code but it still runs like garbage. cylinder pressure meet book specs and fuel pressure is 62 before starting and 68 while running. im at whits end here and have a new coil pack on the seat that i dont want to install because i reallydont think thats it being the misfires are on seperate banks, please if anyone has a suggestion i would greatly appreciate it. thanks guys!

 

[06RangerXLT]

could be: IAC, MAF, Down stream o2, coil pack, or you damaged the plugs putting them in.

theres a guy on here username adsm. look him up, hes a tech.

 

[speedobsession]

thanks, i appreciate it

 

[aspevacek]

Coil pack is where I would have went before swapping all the parts after the spark plugs.

 

[speedobsession]

i was hesitant because ive only ever seen coil packs just stop firing,not misfire ondifferent banks

 

[gribly]

Well, we have what is called a "waste spark" ignition. There's three coils, and the cylinders are paired up on 'em. Look at the coil pack and see how it's shaped and put together and you'll understand it.

 

[jcd302]

I'd go with plugs first if that was the only thing changed (and the wires were right). I've had bad plugs before (when I did the neighbors car).

 

[Duane867]

A bad coil doesn't explain a lean code on bank 2 or o2 codes though. I mean it would have to be so bad it wouldn't even run half the time.
Spray either or starting fluid around the intake gasket you replaced and see if it idles up or down.
A bad ICM can cause alternating miss fires on separate banks as well.