pinging under load

so i've been noticing this chirping sound (or pinging sound). it only happens at a lower rpm when the truck is under a load. i had my dad ride with me, he said it sounds like pinging when a vehicle doesnt get the proper octane. i'm sure thats not it, but its a good description. its just a 2.7, stock truck. its an 05, 72K miles on it, the only thing i think i've replaced is the u joints (and it was doing the same sound before the u joint change). any suggestions where to start looking for the culrpit?

 

When were plugs changed last? Also how is the air filter?

 

^^^ like he said.
You could have gotten a bad batch of gas, has it only happend with this tank of gas or multiple? Fill it up with 90+ octane and see if there is any change.

 

there was a thread about this a couple days ago... had some really good information on it ill search for it

 

http://www.tacomaworld.com/forum/1st-gen-tacomas/151520-truck-not-running-right-hellp.html

 

You say "lower rpm when under a load"... how low is the rpm, and what gear / how much of a load? My 2.7 makes a little "chirping" noise at lower rpm under a slight load but I am positive that's just what the valves sound like under those conditions (my other vehicles have all sounded very similar under like conditions-and I've never owned a v8). Anyway it's important to downshift before the motor starts lugging too much. Also, what is the truck's maintenance history? Has it been cared for?

 

it's normal. this is not a good sounding motor, even brand new it does it.

 

thanks for all the responses.

it has happend over more than one tank of gas

original plugs to my knowledge, i know it says the plugs arent due to be changed til 100K but i dont care what they are made of, i'm replacing them next weekend.

air filter is new

and when i say under a load, i'd say going up a grade about 10% at 2000 rpm in second gear i can hear it. as far as the maintenance, since i've owned it at 40K i have done all the maintenance and it is up to date. i'm real picky when it comes to those things.