97 Tacoma V6 rattling noise when AC is on.. need advice please.

[VaDavid]

I have a 97 Tacoma V6 with low miles on it 34,000 it's a stick shift. Today when i was going up a hill i heard a rattling noise coming from the motor i think it only does this when the AC is on i'm not sure but i do know that it is always when i'm going up a hill usally it's when i'm in 1st gear going to second or secound going to third like if i'm not going fast anough to be in third gear or third gear is to high to get up the hill.

or what i would call luging around in to high of a gear and trying to make the truck go up a hill.

and yes i do know how do drive a stick and i don't do it on purpose

when the truck is just idling you never hear the noise if i push on the gas you never hear it..........i haven't heard it very often just sometimes at first i thought it was the gas but i'm not sure anymore but like i said it's only when going up a hill.

Any suggestions?

[VaDavid]

I forgot to say it is a 4x4.

[Flash75]

Sounds like you are describing pinging or spark knock. It would be a little worse with AC on due the the additional load of the compressor. Try using the truck with AC off and see if you can get the rattle without AC. A noisy AC shouldn't happen only when going uphill. Have you recently changed brands of gas or changed from premium to regular grade fuel? You mention 34k miles, has the truck ever been tuned up and does it still have the original air filter? I assume you do not have a check light on. Your truck should have a knock sensor that will change the ignition timing to prevent pinging, you could have a defective sensor but I would think that should give you a check engine light.

Clifton

[VaDavid]

There is no check engine light on and yes i do get gas from differant stations i had jsut left the gas station a few min before it did it, i used to always use 93 now 87 due to the cost of gas now.

I had the truck at the dealers last winter because of a pinging sound in cold weather on startup they said it was common they cleaned the fuel injectors said it "might" help (it didn't) the nock seemed to go away some when i used 93 gas............ it did sound like the same noise i heard in winter only a lot worse.

[Flash75]

I don't know which fuel your truck specifies but if 93 octane helps it is best to use it. Pinging can be harmful to your engine. You should get a small fuel milage improvement with 93 octane gas. You can try some of the octane boosters but most people say they don't help, if you do try one make sure it's oxygen sensor safe. You can also try different brands of gas and maybe alternately fill with 89 and 93 and see if that helps. You can also rev your engine an additional 2-300 rpm before up-shifting. All these should help. It sounds like you may have a small problem in your engine management system, but finding someone that can solve the problem isn't easy. It seems a common answer is, "That's normal". I have to agree the higher cost of gas is taking it's toll on most of us.

Clifton

[David97]

Thanks for the help Flash!

I used to always buy exxon 93 octane but they are the most costly now i just buy wherever is the cheapeast. I just hope something isn't wroung with my Toyota.