Ive read all of the info about rattling at start up, and other noises. But, i havent really found anything that seems to be the same as what mine is doing. I have the 5.4 and during acceleration, or under a load such as pulling a trailer, or going up long steep hills the motor makes a very noticeable rattling noise. To try and exlplain what it sounds like, The sound "sounds" like, imagine a 30 ball ballbearing missing like 5 *****, and as it spins they are slopping around hitting each other, if that makes sense. Also sounds similar to spark knock, but much more intense. Anyone have this before, or know what it might be. Like i said it only happens during accerlation, and under load. When the rpms are low, or the engine has no load on it, it is not noticeable. Thanks in advance.....

 

How do you know it isn't spark knock? To test for it, start using the highest octane gas you can buy and see if it goes away or lessens.

 

X2

 

I arleady tried that, even mixed in a little race gas one time to boost the octane, still makes the sound.

 

bump....anyone

 

Maybe try picking up a can of CRC Mass Air Flow Sensor cleaner from your local auto parts store. There are threads on here about the proper way to clean it. It has worked for me in the past and it's part of my regular maintenance I do on my truck. It's especially helpful if you have an aftermarket intake like I do which gets cleaned and oiled.

 

one more time, anyone? I will try to get a sound clip

 

Sound clip would be great. Have you pulled your belt off and spun all your pulleys by hand to check for any bad bearings. When was the last plug change? And how many miles on your truck. Any cel's now or recently. Any other issues with the truck. Is there a loss of power when its under load and makes that noise.

I just swapped my old 99 5.4L that sounded like it had a bad main bearing, maybe wrist pins. 2 mechanics thought the same.. which it still could have because I havent checked. It only did it at higher rpms for the most part. After pulling it I'm more convinced it was the timing chain tensioner/guids since there is a lot of slack in the chain and it hits metal to metal.

It could be a number of things. More info would help though
Maybe throw your oil weight and filter type in there too.