hi guys im in need of some serious help i have a 97 f-150 i drove the truck the other day and it was fine parked it around 930 at night it was fine got up to go to work at 4am and it was missing real bad. hooked the scanner up to it and it read misfire on cylinders 3 and 4. this truck has high miles 270k. so i started with the basics plugs wires and to no prevail it fixed nothing. so i looked a little deeper and changed all the heater hoses and the back two plugs again and cleaned the wires just to make sure i didn't have a leak dripping into those two banks and its still missing, so i went ahead and changed the injectors out with the ones from bank 1 and 2 and reset the codes let the truck idle and it re-triggered the misfire on 3 and 4 so its not the injectors. then i did a compression check and it checks out fine. i then did a pressure test with the cooling system and it held pressure for over an hour so i eliminated the intake gasket by that. any help would be great i have been having to drive my turbo car at 4am to work and the neighbors aren't too keen on it

thanks ahead of time

 

If it's not plugs, wires, injectors, or compression that only leaves 1 more thing - coil packs. However, 3 and 4 are on 2 different coil packs, I suppose it's possible both are bad.

Are you numbering the cylinders correctly? 3 and 4 are the back 2 on the passenger side.

 

4.2L V6 has 3 & 4 on the same coil. He didn't tell us what engine he has..... We're only assuming it's a V8.

 

its the v8 section so you would have to assume it a 4.6 or 5.4

 

Reading between the lines on your post leads me to believe that you are seeing coolant on the plugs and or plug wires. You have changed the #3 and #4 sparkplugs twice according to your discription and pressure checked the coolant system to eliminate possibility of the intake manifold leaking and the heater hoses. So with that said are you seeing or did you find coolant on the original sparkplugs and again on the first set of replacement plugs either on the electrode or in the plug well? If you are seeing coolant on the electrode/ combustion chamber side of the plug then you more than likely have a blown head gasket and a hydrocarbon test will be helpfull. If the coolant was on the outboard side of the plug then you may still have external coolant leak and the wires are now soaked in the boot. Anytime you pull sparkplugs look carefully at the electrode end and inspect for coolant,gas, oil, or damage. You did a pretty good job of diagnoising the problem but I think there may be a little more information that we are not getting and could help us.Thanks

 

How many noobs get it wrong anyway...

 

Sorry guys truck is a 4.6 Windsor plant built vin code 6. I have changed the cool packs also already. What other info would be helpful for you dynotech

 

If there was coolant on the #3 &#4 sparkplug electrodes when you removed them. Are you getting coolant in the combustion chambers or in the sparkplug wells? Sounds like you are finding coolant somewhere but I'm not positive where, either external, internal or both. Maybe I'm missing something.lol