Hey guys, I recently bought a 2000 protege SE with the 1.6 engine. It's my first car, pretty much bought to mess around with and learn about cars.

My question might be a basic one but I noticed a split in my air intake tube (the big one that connects to the throttle body), so obviously that needs to be replaced, but I happened to notice something that I was curious about. When the tube is off, the car won't start, and if I pull it off when the car is on it stalls. Why is this?

I assume it has something to do with like vacuum pressure or the mass airflow sensor not detecting anything? that's all I could come up with. Doesn't the tube just suck air in through the air filter? I didn't imagine the air filter would even produce a noticeable amount of air resistance. I've seen youtube videos of people running their cars with the air intake tube off, I don't know why mine doesn't! (just for the record I have no intention of actually driving my car around without the air intake tube on)

Anyways, if anyone can shed some light on this and help me understand how that part of the car works, it would be much appreciated!

 

Replace the air intake tube

The reason why it doesn't start because the MAF sensor that's connected right by that hose is not sensing the right air/ fuel ratio amount to start the car

 

there are two types of intake air systems
1- speed denisty system which uses MAP sensor (manfold absolute pressure sensor) which is installed on the manfold itself ,so the engine does not have any reason to stall when you pull out your intake hose.

2- MAF intake "mass air flow sensor like your engine" which use MAF sensor installed after the air filter and befor the hose you pull out, so the engine stall after you pull it out because MAF sensor will give a reading of 0Volts instead of about 1.2 Volts in normal idle ,this causes the amout of fuel to decrease and make engine stall.