Rough idle at a standstill

I have a 2000 automatic Corolla.



When I start my car (especially the first start of the day) it idles very rough. It's especially rough when I shift into "D" and am not moving. Basically when the car is between 800-1,000 RPMs it idles the roughest. With a little gas, it's fine. But when I pull up to a stop light, it idles and vibrates with a nice rattling sound.



I keep my car pretty well maintained. I am thinking that a little Sea Foam treatment (engine treatment and Sea Foam spray) might help. A friend also suggested that the transmission might need to be flushed, although I have that done every couple years.



Also, where is the mass airflow sensor on this car!?

Reply 1 : Rough idle at a standstill

Also, how do I find the correct vacuum line to add Sea Foam to?

Reply 2 : Rough idle at a standstill

MAF sensor is on corner of the airbox closest to the firewall. Can't miss it - two screws hold it to the airbox assembly and an electrical connector sticks out the top.



Doubt it is your transaxle, I'd concentrate more on the fuel and fire aspects. I'd also hold off on the Seafoam until you determine what exactly is going on, too often, a Seafoam treatment may mask an underlying issue or make the idle quality worse:



- clean MAF

- clean throttlebody, make sure to get around the throttle plate

- run some injector cleaner to clean the injectors

- read spark plugs and verify that the plugs are gapped correctly and clean

- double check chassis grounds, as this car tends to be very sensitive to electrical noise