4.6L Engine Rattle when accelerating.

[morris_506]

I have a 98 f-150 4.6L 5spd that has a wierd rattling noise coming from what sounds like the engine. The noise will only happen when the truck is in gear and under a load. It will not happen if I keep the RPM's low, unless I am going up a hill. When I rev the truck in neutral, the rattling noise isn't there. Also when I'm driving and hear the ratling noise it will go away when i push the clutch in(which im guessing takes the load off) but will come back when i let out on the clutch. Seems to happen most when I'm in gear and trying to accelerate. Any help would be much appreciated!!!
Thanks.

[torkum]

New plugs and mid grade fuel might fix it. Probably detonation happening or alot of carbon build up on the valves.

[morris_506]

Thanks. I am definitly gonna start there. I will post again and let you know how it worked!!!

[torkum]

If you've never replaced the plugs on a Triton before do research on how to do it. Make sure the motor is overnight cold, vacuum out the plug holes before pulling, use plenty of penetrating oil, and make slow 1/4 turns. Don't over tighten when replacing them and fill the spark plug boots with dielectric grease.

[morris_506]

Hey there,
I replaced the plugs and the wires and it still has a rattling sound when accelerating or under load. Could it be a partially blocked catalyic converter causeing this rattle. I am also getting p0171 and p0174 error codes.
Thanks.

[93 mix 'n match]

drive the truck until running on fumes and fill it with the high octane fuel. mine does that when it runs on regular. id almost guarantee it will fix it.

[Mike-G]

I have the notorious exhaust stud rusted away issue and my truck sounds it's worst when I pedal down. Might want to take a look at your exhaust manifolds.

[Mucifer]

Originally Posted by 93 mix 'n match

drive the truck until running on fumes and fill it with the high octane fuel. mine does that when it runs on regular. id almost guarantee it will fix it.

Mine did this for years. Bought in 2000 with 28,000 miles on it. Fast forward to 2017. Still runs strong with 192,000 miles still with original engine and transmission. Been running 87 octane for years. Even filled up with Shell 92 octane only and still the engine rattled under load (Sounded like metal ball rattling around in a spray paint can). Never rattles when revving engine in neutral. Waited until I was running on low fuel light. Threw some NOS Racing formula Octane Booster 12010 and 22 gallons of Shell 92 octane. Cleared that rattling under load noise completely, the same day. Thanks for the hot tip. Much appreciated.

[Sycoholic]

Those error codes indicate a lean condition on both banks. Vacuum leak, bad maf are probably the most common. The computer monitors the o2 sensors as well as others and adjusts fuel trims. If the maf is dirty you'll get false readings which lead to this. If there's a vacuum leak it'll throw extra fuel at it to compensate and kick those codes as well. You'll need to look at fuel trims to really get an idea what's going on.

[shooter123]

I second what sycoholic said, same thing on my own truck. cleaned the maf with the crc maf cleaner and found my vacuum leak, no more ping/rattle.