[cavanaugh482]

With car started, idling in park. When defrost is turned on the idle surges up to around 2k then drops back down to normal, when i switch from defrost to heat the idle drops way down and engine sounds like it wants to stall for a few seconds before idle returns to normal.

Any ideas?

 

[C J]

Is it throwing any codes?

 

[cavanaugh482]

Is it throwing any codes?

No, not throwing any codes.
Doesnt happen until engine is warmed up.

 

[C J]

No, not throwing any codes.
Doesnt happen until engine is warmed up.

Well...if any sensor is tripped then it will throw a code. So that makes me think it is mechanical? Maybe a filter?

Any mechanics here want to take a guess?

 

[Munch]

When you switch to 'defrost' I think the A/C starts which engages the compressor on the engine. That triggers the increased idle from the compressor load on the engine. Then when defrost is switched off, the compressor disengages and idle will drop. Perhaps there is something going on with the sensors for that process that needs to be checked out.