I've got a knocking/clicking noise that only happens at idle. Recently had it smogged so I imagine they would have caught an exhaust leak. '99 4Runner w/ 140K miles...haven't tried higher octane gas but I thought that engine pinging primarily happens when revving... Thoughts? Thanks in advance.

Detonation is the knocking you refered to. It usually is most pronounced under load or acceleration not so much at idle. The noise is likely from some other source.

Is the ticking something new?

Fuel injectors make a small ticking sound each time the actuate.

Some times a sticky valve can make a tick/tap noise as the cam lobe hits it.

Maybe some Sea Foam in the oil and fuel could help clean it out.

Thanks Kutter. Will try some Sea Foam. Yes, the sound is new as of about 3 weeks ago. It is louder outside the car than it is under the hood. Seems to come from underneath as I can hear it best near the driver's side wheel well.

Did you ever figure out the knocking/clicking at idle?

My 1999 4runner 3.4 115K started clicking about 3 months ago. It isn't constant, but will happen in PRN&D. It sounds like it is from the bottom of the engine. It will always quit if I depress the gas pedal, even if it only raises the rpm from 800 to 900. I have used full synthetic oil since 40K and high octane since 50K when I installed the supercharger.

I took it to my Toyota dealer and they said it was in the transmission bell housing (11 hours $1,055 in labor just to remove and inspect). Needless to say I refused and am looking for a different answer.

I cant believe they charge 11 hours for a job like that, should be able to be done in less than half that time...

Does your supercharger chatter in the nose drive?

Make sure your crankshaft pulley bolt is tight i.e. make sure it has been torqued down to spec.. If not, the pulley will rock on the crank (sounding like a rod knock)...

If it were loose it will eventually bugger up the crankshaft...

No nose drive chatter, but I did read Gadget's information and similar 4x4wire posts. I do plan to change the oil on the S/C as it has 65K on it. It will be interesting to see if there is any metal in the oil.

Posting must have scared off the noise demon as it has only occurred once since posting.

Still need to check the crankshaft pulley.