G'day folks, after some feedback from others with zze122's r.e. engine rpm when cold. Mine will hit 2000rpm on a cold start up then return to around 1500rpm and progressively less as the engine warms up. IAC valve is clean and free. Is this normal of this model? Mine is an '02 model with cable throttle.

 

Also regarding the IAC valve, it has coolant flowing through the end of it and I can't for the life of me work out why?

 

Thanks for reading.

Sounds normal.

G'day folks, after some feedback from others with zze122's r.e. engine rpm when cold. Mine will hit 2000rpm on a cold start up then return to around 1500rpm and progressively less as the engine warms up. IAC valve is clean and free. Is this normal of this model? Mine is an '02 model with cable throttle.

 

Also regarding the IAC valve, it has coolant flowing through the end of it and I can't for the life of me work out why?

 

Thanks for reading.

 

Sounds normal to me. The IAC has coolant running through it because that is how it measure the temperature of the engine - in older cars there was a wax pellet inside the IAC valve which softened/melted at a certain temperature from the coolant flowing around it, which stopped pushing against a spring and caused the idle bypass valve to shut, lowering the idle speed as the car warmed up. Newer models simply replace the wax pellet with a temp sensor, but it is still located in the throttle body so coolant is still circulated through it. Also, flowing warm coolant around the throttle body improves emissions (pre-heating cold air, same way old-skool engines had a shroud around the exhaust hooked up to a pipe running to the carby to better atomise the fuel in the manifold and prevent carby icing)

My ACV36R Camry does the same thing.

Thanks Hiro. No temp sensor anywhere near this IAC so I'm guessing it's there for pre-emission control like you say. On another note, any tips for these models regarding pinging? I'm thinking mine has a lazy knock sensor. Once at operating temperature under light load it will ping badly, load it up a little more and it stops pinging. Tried premium fuel last fill and no change.

Thanks Hiro. No temp sensor anywhere near this IAC so I'm guessing it's there for pre-emission control like you say. On another note, any tips for these models regarding pinging? I'm thinking mine has a lazy knock sensor. Once at operating temperature under light load it will ping badly, load it up a little more and it stops pinging. Tried premium fuel last fill and no change.

 

http://au.toyotaownersclub.com/forums/topic/2068-throttle-body-coolant-bypass/

 

Seems in this case it is just for throttle-body de-icing, something which is an issue in cold Japan and North America but not really an issue here, but bypassing it can help with heat-soak issues.

It has nothing to do with the IAC. Its just to prevent ice from forming on really cold days.

 

 

Yeah my 2003 rolla does the same thing... i don't like it!. I think its really stupid that Toyota did that... no other cars do that. Its not needed. There were times when my car would hit like 2300rpm on start up!!. Ridiculous.

Edited April 23, 201511 yr by Marek0086