Hi, my carlo has been idleing high for a while now. It varies between anything over 1k and up to about 2k rpm idle...

I am thinking its the o2 sensor... does anyone know how hard they are to replace?

I have a 99 monte with a 3.1... i am thinking about taking the sensor off my old carlo (same model) and putting it in the new one... not to sure how difficult this is, or weather or not I should just buy new...

any suggestions on the matter?

Thanks!

 

1. Check for vacuum leaks, does the idle go up and down?
(spray starter fluid on lines and gasket areas)

2. Check your throttle position sensor, mine was bent and idled at a steady 2k.

 

O2 sensor prob wont cause a high idle.

like said check for vac leak. an idle that high you might hear the sucking sound of the leak. if not use the spray method to find it. spray starting fluid around and when you hear the rpm change/ sputter you found the leak.

the 3100/3400 series engines have a history for leaky lower intake gaskets. mainly they just leak coolant but i guess it could leak air too. are you loosing any coolant? or your oil look like water got in it?

 

Vacuum leak. Check that first. O2 should not have to do with idle like that. BTW - O2 sensors should be changed around 70-100K miles (the elements brake down over time).

You can also try cleaning the tunnel on the upper intake that goes to the EGR (even if it's not part of the problem, the 3100s do have that tunnel gunk up).

 

I'd look into the IAC valve too.