Ok so I have a 98 civic EX 5spd and when warm sometimes the IDLE will drop to around 500 or less has been known to actually stall once in a blue moon. I did search and some have said the IACV and some have said the O2 sensor. I dont want to spend a bunch of money but i want to fix the problem. I have a Pioneer Indash Navigation that has a volt meter and when this idle problem occurs then the voltage will drop ot around 11.4 ish and it will run normally at 14.4 so what can it be should I start with the O2 sensors??

 

Yes start with the O2 then go from there.

 

Thanks thats what I thought and would it be the upstream or downstream sensor??

 

I'm thinking its down stream go with the cheapest. put it in if that does not work see about returning it and try the other. Also look at the map senser.

 

the second one is for monitoring purposes ONLY. It will not change how the car acts. Changing the secondary one will do nothing.

 

I completely agree with Mugan. Return parts if they don't fix the problem; however, first ask the store about their return policy to avoid potential problems.

I would also suggest that you try cleaning the IACV with carburetor cleaner before replacing the O2 sensor.

Given that low voltage may precede your low idle problem, you might eventually also want to consider that your alternator may be on the way out.

Finally, does the Check Engine Light turn ON when you have the idle problem?

 

No CEL and the ALT is new!!! so it better not be on its way out.... but there is always the chance. I will check the IACV and then the O2 Sensor

 

You need to adjust your idle and get any air bubbles out of your coolant system.

 

Thanks will do tomoro and then let ya know what happens