My 4.7L has a slight misfire thats able to be heard through the intake, especially when first started, and it can be felt in the truck at idle. It feels like a slight vibration.

It has 106k on it, I bought it at 103 and replaced the champion plugs with some bosch oe finewire platinums. Oddly enough, I added a dose of marvel mystery oil and it seems to idle and rev smoother but it does still miss. No codes ever come up.

Truck did sit for a little while before i bought it, could I have a stuck valve? Should I keep putting MMO in the oil?

 

compression test, leak down test, or just drive it eventually a light or code will show up.

 

If I had compression issues wouldn't I be burning oil? Truck uses just about no oil in 3k miles. It runs like a top, gets 16-17mpg in my stop go commute, and timed my 0-60 at 7.5. I've ran fuel injector cleaner in it as well. I'll just keep on truckin til the light comes on.

 

What year is your 4.7?

You don't have to be burning oil to have a compression issue. A burnt valve can cause a miss and it won't burn oil.

First thing I'd do is get rid of the Bosch plugs and put in OEM Champion RC12MCC4's. The coil packs are designed for a copper plug.

 

Its an '02. Do these engines really despise anything but copper plugs that they'll miss? Im at the end of my oil change, so I'll replace a quart of oil with more marvel oil, run that for a while and see how she does. I'll probably just swap plugs too, its easy on this motor.

It's odd because this truck had been maintained by the dealer all its life, PO had all the records.

 

I'm not going to say that Champion plugs are great, I'm neutral in that aspect. The engine, when tested, was designed to use those plugs however. Copper also conducts electricity very well. Sure some plugs last longer but as you said "it's easy on this motor" to change them. Besides, you then get an idea as to how the engine is running by reading the plugs.

From the FSM:
CAUTION: The 4.7L V–8 engine is equipped with copper core ground electrode spark plugs. They must be replaced with the same type/number spark plug as the original. If another spark plug is substituted, pre-ignition will result.

 

So the bosch 6275's I'm running are also heat range 8, where as the oe champions are 12. Would that have any postive/negative affects on a stock motor?

 

According to the Bosch heat range conversion chart, a Bosch 8 = Champion 12.

 

Hmm, I wasn't aware of the heat range conversion. I'll replace those bosch plats with either champion coppers or ngk v power coppers. Cant go wrong with ngk, and they seem to be well liked from what I've read. If it cures the misfires, great. If not, atleast I'd know.

 

If it was me, I'd try the OEM Champions first, just to see what happens with the misfire. If it resolves then you could try some other plug.