A bit of a dumb question ...

I always wonder ... how do our engines rev higher when cold if the car has no DBW (talking about 2005 and earlier models)? (I know the car does it purposely so that the engine will be brought to optimal operating temp quicker)

Since the throttle position is fixed by the cable at idle / when the gas pedal isn't depressed ... does the car just inject more fuel for the engine to rev higher? i.e. the engine's running super rich?

Just curious ...

 

My assumption would be the cable has less play in it when cold than hot.

 

Idle air control valve plus your coolant temp sensor. The coolant temp sensor senses that the motor is cold so it allows more air to pass through the motor (through the IACV), even with the butterly on the throttle-body closed. It does that to warm it up to operating temp.

 

What is IACV?

I thought the throttle plate is the only way for air to come in? At least I don't see where else the intake feeds air into other than the throttle body

I guess my question is ... how does more air come in, when the throttle position is same at 1.5k and at 900rpm (cold vs warm)

 

very good question I always wonder about this myself

 

lol.

 

Just what he said.
It's part #17 in the upper right corner of this diagram.

 

You know, cruise control works on non-DBW cars....

 

The Idle Air Control Valve is located on a small passage around the throttle plate. If you pop your intake off you'll see a couple holes in front of the throttle plate. One is the iacv port. When the ecu sees a cold temp it cycles the iacv open and closed very quickly to allow a metered amount of air in. This small amount of air is plenty enough to raise the idle under no load.

 

Cruise control actually pulls the throttle cable though ... and the gas pedal is actually physically depressed when cruise control is on

However, the gas pedal is still at its neutral position when the car first starts up