Rattling in my engine?

Okay I got a problem. When I drive up a hill, or really step on the gas I hear this rattling sound in the engine. It really only happens when my engine is sort of bogged down from either the hill or me stepping on the gas. When my engine catches up the sound goes away.
I took it to a mechanic, he drove it, heard it, and says he doesn't know what sound it is but there's nothing wrong with my truck. My last Taco did it too. Has anybody had this problem before?
Wish I could do a sound clip, but it only happens when I drive it and put some pressure on the engine.
Please help!

 

Is it a rattling sound or an engine PING?

My 3.4L used to ping going uphills under torque (gas).

If you think the engine is pinging - try a different (higher) octane gas.

 

Mine does the same thing going up a hill you hear a slight rattling noise. I have the 3rz which is the 2.7l. My only guess which is prob. no where even close because I AM NO MECHANIC by no means whatsoever, is maybe the valves rattling. But like I said I have no idea and would like to know exactly what it is also.

 

yes this exactly what i'm thinking.higher octane and maybe a different brand.

 

It really sounds more like a rattling in the engine. I actually already put premium gas in it because it has the supercharger and I've done that since I've owned it (which is just only about a month). Maybe I'll buy some sort of fuel additive and see if that helps, but I'm thinking it's something different.
Either way it drives me CRAZY! I mean, you want to show off your truck but when it's under torque it's got that spuddering rattle sound, insane! I want to fix it!
I'll check out what was suggested and see if it helps.
Any other ideas guys?

 

That was my next thought..... check the SC and make sure everything is still tight - and whatever maintenance it would need.

 

I don't know because I just bought the truck and I didn't ask when and if he had done it recently.
I'll have to check that out, maybe take to get serviced at the dealership. Great idea!

 

I had a 3.0 Ford engine that used to do that in hot weather. Using 89 octane solved the problem. It can't hurt to give it a shot.

 

Awesome! Thanks! I'll check this stuff out this weekend.
Thanks!
I'm also going to see if I can find out when and if the S/C has been serviced and who will do that.
Thanks for the ideas guys!

 

My truck only has 44,000 miles on it.

 

Right on! I don't know if they were done at 30k cause I didn't own the truck at that time....so.....better safe than sorry and just I'll set up an appointment to have the Iridium plugs put in and see what that does! Thanks!!

 

So far....
I have replaced my stock air filter with the afe pro dry and I haven't heard the rattle except for once. (in fact I only barely heard it once when I really gave it some torque going up a hill - but NOTHING like it was before!!)
So...whatever that did it seemed to work. I'm still planning on replacing the plugs this week or early next week. I figure it can only help and might fix it completely. I'll keep you updated.
Thanks for the suggestions!!!