ok so i was driving my truck on a 300 mile trip and i noticed that when i stepped on the peddle and it did not jump a gear that you would hear a rattling noise. i have noticed it before but its getting louder now and happening more often. i looked under the truck and theres nothing loose. this rattle happened before i changed my plugs and after so its not a spark plug knock, but i still have no clue what it could be and theres no power loss either. also its a 2000 f150 5.4 86k.

thanks

 

check the exhaust heat shields.

 

yea i did, they all seem pretty solid

 

what brand and type of oil do you use? and what oil brand filter? does it matter what octane gas you use? do you know where its coming from?

 

valvoline 5w30 full syn, motorcraft filter, not sure, and it sounds like its coming from right in front of the drivers seat.

 

It could be spark knock (detonation). Try a tank of premium gas, does it go away?

 

It might be your cats. Mine does it only when I am at a dead stop and step on it pretty hard. That's what it was on mine, hope that helps.

 

tried the premium gas and it worked, no more annoying noises. so what do i do next, seafoam? what do you guys recommend?

 

I'd spend the 75 bucks for a Motorvac or BG intake cleaning job. Doesn't hurt to do one every so often anyway, I had one done at 84k. You could try a bottle of Techron in the gas and see if it helps enough to stop the ping. Another option is to try different brands of regular gas. What you have are combustion chamber deposits, raising the compression, and also creating localized "hot spots".

Did you use Motorcraft plugs?

 

yes i did

 

and will seafoam do the job?

 

Seafoam in the gas tank won't do much at all, Techron is just as effective if not better. Pouring it down the brake booster vacuum line has dangers involved, such as dumping it in too quick and causing a hydrolock. I would REALLY recommend the Motorvac or BG job, because that also cleans the throttle body.

 

what's a BG job?

 

It's where they hook a machine up to the intake and run the thing on chemicals. Most Ford dealers have either a Motorvac or a BG machine, as do a lot of independent shops. Motorvac and BG are essentially the same thing.

 

thanks glc, you've been a big help