2003 Toyota Rav4. 4 cylinder, 145k miles. Recently started making a ticking noise. Noise only happens on startup and for about 15 minutes and ONLY when under load. So, start the car and fast idle sounds normal. Put it in gear and start pulling away and you hear ticking. Not rod knock. Clicking sound like playing cards in your bicycle spokes, but louder. Push in the clutch, get off the gas at a stop or going downhill, no ticking, no backfire, nothing; clean idle. Engine gets hot and you don't hear it after that. Obviously little worrisome and annoying.
Tried: Ran oil flush/refill, still ticking. Tried thickening oil with STP - still ticking. Reloaded with straight (non-ethanol) gas - still ticking.
Plugs were replaced and the air filter was also replaced. I've done all I can think of that's fairly easy. Any ideas? Only things I can thing of is to try cleaning the throttle plate, MAF, cold air throttle positioner.