Slight RPM drop during cold weather

Maintenance/Repairs
1

I have a 2000 Corolla CE with 51k miles (bought a couple of months ago).

It ran perfectly during the hot weather (75-80F) and it idles around 650rpm-670rpm. These couple of weeks, there have been very cold weather (60-70F) and it idles mostly around 650rpm but can drop to 630-640rpm. Sometimes, it will suddenly drop to around 612rpm (there will be a very slight shudder) and pick back up to 630rpm. This is with all accessories turned off.

If I turn on the windshield wiper, then everytime it activates, it drops to around 612rpm and picks back up quickly. This only happens during cold weather.

I don’t think it’s the MAF sensor…any idea what it could be?

2

Could the operation of the AC be the cause?

3

I would clean the IACV (idle air control valve) and pour a bottle of Chevron /w Techron injector cleaner in the gas tank.

4

Dropping to 612 and shuddering and idle rpm involvement w/the windshield wiper means there is definitely something wrong. There are numerous things that could cause this. The suggestion above it is a good one. If it were my car though, the first thing I’d do is make sure all the routine maintenance is up to date and check for vacuum leaks.