'04 Expy 5.4 - p0306 not resolved by changing plug. Truck shaking.

[Adieu]

Was the oil on the electrode end or the the insulator end?? If the oil is inside the engine, you are looking at bad piston rings or valve seals. If the oil is only on the body of the plug, then you are looking at valve cover gaskets which is doable.

COP boots are crap, coolant/oil or general crud in the spark plug wells CAN just be a lousy coil boot and shit getting spilled during routine maintenance....

 

[plumcolr]

Swap the coil with another cylinder and see if the code moves with it. I had continuing coil issues with my '06, with them failing one after the other. Finally swapped out all 8 with a set from summit racing (MSD) Cos about $150 for all 8.

 

[Fat Slob]

The learning computer can compensate for a LOT of weird engine anomalies, it's pretty smart. It allows for a really efficient and specific tune for your specific engine weirdness, since no engine performs identically.

It can also be super weird when that weirdness changes or goes away.

So when there is a bad plug does the computer tune engine so it performs as well as possible with the bad plug in place? And then the computer re-tunes back to a more normal range once it synchs the new plug?

Just trying to understand what the computer actually does when a bad part is detected.. I know it will disable the engine or limit it tremendously to prevent damage (limp mode or whatever its called). We had a coolant issue one time and it shut itself down.

 

[plumcolr]

In my 06 the computer cuts off both spark and injector to misfiring cylinder, re-enabling every couple of seconds to see if situation improved.

 

[Fat Slob]

Swap the coil with another cylinder and see if the code moves with it. I had continuing coil issues with my '06, with them failing one after the other. Finally swapped out all 8 with a set from summit racing (MSD) Cos about $150 for all 8.

So far the code hasn't returned and she's running well, knock on wood. If the code does return I will try to swap the coils. Thanks for the input.

 

[Fat Slob]

In my 06 the computer cuts off both spark and injector to misfiring cylinder, re-enabling every couple of seconds to see if situation improved.

Sounds like that's what mine was doing as well.

 

[deweysmith]

So when there is a bad plug does the computer tune engine so it performs as well as possible with the bad plug in place? And then the computer re-tunes back to a more normal range once it synchs the new plug?

Just trying to understand what the computer actually does when a bad part is detected.. I know it will disable the engine or limit it tremendously to prevent damage (limp mode or whatever its called). We had a coolant issue one time and it shut itself down.

Yep, it can mess with the ignition AND valve timing too to see if it can get that cylinder to fire properly. From valve timing alone it can change exhaust recirculating and air/fuel charge size. The engine moves in slow-mo for the computer. It monitors sensors hundreds of times per second, many times more frequently than even the best scan tool will show you. It can tell based on how quickly the crankshaft moves during a given cylinder’s power stroke how efficiently it’s burning and adjust to compensate. This is also how it detects misfire. I’m not sure if the VVT solenoids react quick enough to change valve timing for a particular cylinder only, but the computer definitely could.

It then learns what’s normal for your engine and remembers approximately what settings it needs for most efficient operation but when you change one of these things it will have to adapt again, but since it already has “learned” so much it takes a while for these averages to change. When you reset it by disconnecting the battery it has nothing to go off but Ford’s initial parameters. Once you’ve corrected an error condition those will be much closer to optimal than before, so it doesn’t take long before it’s optimized again, unless something else is wrong.

 

[Fat Slob]

Now another plug is fouled and covered in oil. Heavy amount of oil in there

 

[deweysmith]

Now another plug is fouled and covered in oil. Heavy amount of oil in there

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