Idle problem at startup

[Benoit]

Car: Toyota Corolla 2004, manual Transmission, 150 000km on car.
This only happen when my car is cold. I start my car and revolution goes up around 2000 rev/min. But about 5 to 10 sec after I've started the car, rev drop down to 1000 rev/min and car start shaking...and after 5 to 10 sec of low rev, car goes back to it's normal 2000 rev/min.
This started 3 week ago and it do it every time I'm starting car when engine isn't hot.

 

[NHGUY]

Temp sensor maybe? The engine does not know wether its hot or cold.

 

[JC1]

Benoit,

Check Toyotanation.com to see if it's the IAC (Idle Air Control valve). It may need cleaning with some throttle body cleaner.

Regards, JC.

 

[mechtech2]

Sounds like a vacuum leak.
First, clean the TB and idle air valve really nice.
Then manually check for vacuum leaks at all lines and connections. Also the intake.
Maybe get some spray MAF cleaner and clean the MAF sensor.

Do these thing properly, take your time, and see how she runs.
If it doesn't fix it, these things are still necessary.