2000 Avalon 115900 millage. Sometimes won't start. If I turn the key (cranking) and push the accelerator at the same time, it may start. What's the problem? Thanks a lot!

I always troubleshoot using these basic principles. An engine needs the following:

1. Air
2. Fuel
3. Spark
4. Timing

AIR
- make sure your airfilter is clean. Check that your PCV valve works.

FUEL
- fuel pump failure is common especially if in the 100K milage it's never been replaced. If there is a whine coming from your tank, or you can not hear the pump engage (meaning just before you turn the key all the way you can always hear the pump pressurize....sometimes having a friend turn the key and you listen at the filler hole will work).

SPARK
- how old are your plugs ? Pull one out and inspect.

TIMING
- if your engine runs nice once it starts then it's not your timing. Loping will usually point to a worn timing belt.

My car has been doing that exact same thing. I dunno why it's like that. I think maybe due to the sudden cold spell where I live we got snow in the spring... and I had my car sitting outside. But, I'm not sure why it's having trouble starting up lately.

Another suggestion is to remove the cap from your distributor and replace your rotor. The rotor is very cheap and is the first thing that wears. The larger the gap, the weaker the spark and it wears before your spark plug wires.

It is also significantly affected by humidity if the gap is large and is a key thing to check if there's hard-starts. Secondarily, you can also check your distributor "cap" for cracks.

Avalon doesn't have distributor or rotor.