razzle

I was towing my two snowmobiles home from new york yesterday and whenever I was going up a hill my truck had this rattle noise coming from the engine. No noise on flat ground only when going up hill. No loss in power. Its a 06 fx4 5.4 with 51,000 miles. replaced the plugs 2,000 miles ago. Any ideas?

razzle

Would oil weight cause this?

dixie_boysles

was it only under acceleration? Im wondering if you could be developing the exhaust manifold leak. Mine wasnt that bad at first, like you said, only under load. But now under ANY acceleration, i m getting a rattle/ticking. come to find out, its the passenger side manifold and you can hear it it coming from under the passenger side floorboard really well.

razzle

I live in NJ and its flat here so I dont hear it at all even if I get on it. It was when I started up a hill and as soon as I got over the top it went away. It made the same noise with or without using cruse control. kind of sounded like a low octane knock.

Disposablehero

Are you sure it's not detonation/pinging? Could be just bad gas or something alot worse. I'd put some techron in it first and give it a go.

razzle

It does sound like an exhaust leak.

picaflor

Do you have turned O/D off, right?

razzle

I ran it with the od on and off, same noise. went through three tanks of gas, still have the noise. hard to pin point because its flat where I live and it doesnt make the noise here.

dixie_boysles

do me a favor, crank it, leave in park, press brake and give it some accelerator at the same time WITHOUT spinning tires. if you hear the ticking/rattling noise its more than likely exhaust manifold leak. Have someone else walk around front end while doing this with their ears listening at the front fender wells.

put it back in park, then rev it up. if you dont hear the same ticking, i can almost say it IS exhaust manifold/

razzle

Just tried it. no noise