I have a 1998 F150 that we have owned since it first left the lot at ford. For the first 75000 miles or so it was a great truck with a nice lift kit and 35s (i still need to change the gears). Then a spark plug ejected from then engine. Not much later had to replace the engine, this was a couple years ago. The diagnoses was a spark plug fell apart and destroyed the block or something. Not exactly sure it was my dad's at the time. Well ford replaced the engine and first thing i notice was how dirty everthing look under the hood... Well it looked like ford only replaced the block but reused the intake, fuel system, and i think even the heads. Well for the past year its been acting up. For example under load/up a hill at higher rpms it make a large rattling noise, like a loose shroud or something. Didnt cause any problem for a while and ford couldnt find anything. Well one day driving on the toll road up a big long hill the noise got extremely loud and then soundly i lost power. The engine continued to run but i had to crawl up the hill and back home with the engine light blinking, engine missfire i think #4. So pulled the spark plug and the was no gap. It looked as if something contacted it. replaced the rest of the plugs, some white indicating running lean. Ran injector cleaner and cleaned the mass airflow censor to hopefully fix the leaning problem. well the engine ran fine but under load still had the rattle. tried higher octane and it helped quite a bit but not worth the extra cost with a low mpg vehicle. well now here and there i get phantom miss fire codes and rough running wich goes away for the most part when i clear the code. I NEED HELP or im gonna sell it, which i dont wanna do.

thanks for any help or suggestions

PS i hate the deep spark plug holes, when i play in the water and mud they fill up and short out stupid engine!

 

The plug was destroyed by detonation. You need to take it to the dealer and have a reflash dome on the PCM. It has too much timing advance. Common problems on 98 models. Also you might want to change the fuel filter to make sure it isn't partially clogged, causing it to lean out under load.

 

Thanks ill give it a try. I have already replaced the fuel filter. Any idea what is causing the rattling? or is that just a side effect of running lean?

 

It is predetonation from either the timing advance being too high or a leam mixture which raises cylinder temps and causes the fuel to ignite before the plug fires. So, when the plug does fire, the two flame fronts collide causing the rattling noise that you hear. Left untreated, it can eventually break a piston ( I've done it in an old Road Runner before)
The PCM used in alot of 98 trucks was tuned for the NASCAR edition trucks which were standard cab shortbed trucks with a better flowing exhaust. When used in a heavier extended cab truck, the extra weight puts more load on the engine which causes the rattling noise.