2003 4Runner V6 Mystery Starting Problem

I recently had a problem starting my 2003 4Runner (V6) SR5. Upon cold start in 80 degree weather, a loud repetitive noise occurred. It sounded as if the fan was hitting up against something. I immediately turned the engine off and tried again. This time it was a little slow cranking, but started, and with the same noise. But I also noticed an odor as if something was burning. I immediately turned the engine off again and waited until the next day. The next day, the engine would slowly (very slowly) crank, but would not start (did not notice any odor.) That's when I called a tow truck and towed it to Toyota's service department. Toyota didn't get to it until 2 days later; however, they told me that upon starting the engine, everything sounded and checked out normal. Sure enough, when I picked up the vehicle, it did not display any symptoms. I call this the mystery starting problem.

Anyone encounter a similar problem???

Thanks for any help or info.

Same as the other guy. I bet it's a moisture/ignition thing. Don't worry about it unless it happens more often.

Same as the other guy. I bet it's a moisture/ignition thing. Don't worry about it unless it happens more often.

Thank you Brian R. I think moisture is a good possibility.

But what would have caused the loud repetitive noise? An animal, like a mouse, possibly stuck in the engine compartment somewhere? But where? I checked the fan, and there was no visible sign of a mouse in that area.

Thanks again for replying.

Without hearing it or seeing it, I can't even guess. If it doesn't happen again, don't worry about it...

You can try looking for some area of the shroud or belt area which shows a spot where there was rubbing.

Maybe someone who has solved a similar problem will post.