Nagging, rough idle
 

The title really says it all... The car doesn't stall but at times, it feels like it could at any moment. Here is a list of everything that I've recently done to try and combat this issue:

- cleaned MAF sensor
- replaced PCV valve
- cleaned throttle body and IAC valve
- new engine air filter
- added a can of sea foam to full gas tank

The old PCV valve was notably dirty.

Before cleaning the throttle body/IAC valve, I noticed that I couldn't manually push the valve open with my finger. (granted, I didn't try as hard as I possibly could or anything) When I cleaned the throttle body and IAC valve, I removed it completely out of my car. Mine was held on by 4 bolts, one electrical harness and 3 hoses, 2 of which were coolant lines. I cleaned it up good and noticed that I could now manually push the valve open with my finger. I then put everything back together and added the sea foam.

I can tell somewhat of a difference with my RPMs when going through gears 1-3 and I can tell that the throttle is more reactive now. BUT, I really don't think I'm idling any better. Also, my avg. MPG reset after this procedure and has actually decreased about 6 MPG as well...

Any thoughts or suggestions as to what my next move should be? And could this ongoing idle issue be doing any damage itself?

Is this a 2004 4-cylinder?

Yes. 2004, 4-cylinder

This engine does not have an IAC valve, were you trying to move the throttle plate? The engine computer sets idle. Try this:

Remove a battery cable, then wait a few minutes and reconnect it. Start engine, place trans in drive with brake on and let engine idle and determine what happens. The computer may now adjust the electric throttle to the appropriate idle RPM.

Note, upon reconnecting the battery if equipped and set the Toyota alarm will go off so be ready to turn it off. If the car has a Toyota navigation system or some kind of radio with an anti-theft system don't disconnect the battery, but post back.