1999 Tacoma 3.4l Idle issue

I have 1999 Tacoma with 3.4l Auto trans with idle issue. I have replace Plugs, wires(the three of them), cleaned throttle body, changed air filter, replaced Idle Air Control valve(had trash in it), checked for vacuum leaks,etc. and still cannot get it to idle below 2100-2200 rpms. Truck runs great other than it will not idle down. I got it to idle down to 1100 rpms last Saturday after adjust idle screw and checking for loose vacuuum lines,etc. Two days later idle is back up to 2100-2200 rpms.
Anyone got any ideas where to start with this issue. I've never run into anything quite like this before. Thanks in advance for help.
Ronnie

 

Wow, posted this almost two weeks ago and still no response. Any techs out there with ideas on what direction to go on this? Thanks in advance for any help.
Ronnie

 

except that the problem with mine is that the engine idles rough, stumbling and sometimes even stalling. I'm going to check the IACV tomorrow. One person told me to check the EGR valve, but I don't think we have one on the 3.4

 

Have you checked the throttle opener mechanism? It is the small round dash-pot looking part on the throttle body with a vacuum line leading to it. It may have a broken diaphragm, which could cause the rod to extend and bump up the idle. See if it is extended and pushing the throttle open. Then try disconnecting the rubber vacuum hose and then connecting it to a vacuum gun to see if you can get it to retract. Basically, if you were to pinch off or plug this vacuum line to the throttle opener, the idle should raise up to anywhere between 900 and 2000 rpm which could be right on par with your complaint. I don't think this is sold separately from the throttle body, so if it is broken, you will need to visit a junk yard or buy a new throttle body.

 

You do have an EGR, and it can cause this issue if it is sticking open.

I didn't realize this thread was so old.

 

Guess I resurrected it gotta find that EGR valve. So many places for a vacuum leak....

 

Vacuum is required to open the valve. If your EGR is the culprit, it will most likely be sticking open. A vacuum leak for this mechanism would likely cause it to not work at all, and you should be getting a code for EGR insufficient flow because the EGR temp sensor will not see an increase. Also, if it is constantly stuck open, you can get an excessive flow code. If it just sticks open for short periods and causes the truck to sputter, it may not be long enough for the ecm to set a code.