surging idle 2001 tacoma 2.4l

Hello, I have a 2001 Tacoma that had been setting up for a while. Having problems with a surging idle. When 1st cranked up cold, has fast idle which is probably normal to warm up. After warm, the idle surges app 700rpm to 1200 rpm (just guessing). I have tried several fixes with no success. I have replaced: 1)Throttle position sensor, 2)Idle air control valve, 3) Mass air flow sensor. I have checked/cleaned air filter, removed and cleaned throttle body-new gasket, checked for vacuum leaks (found none), tried re-setting the ECU, even ran a can of sea foam in fuel tank (as advised by local mechanic), can't seem to find anything wrong. The only things I haven't looked into are: O2 sensors, EGR or PCV valves. I have even taken it to auto repair shop. Still has surging idle. The motor runs good when you are driving the truck, just won't idle normal. About to throw in the towel on this one. I would appreciate any kind of suggestions or advice to resolve this issue. Thank You, Ben.

 

Well, PCV is cheap to replace, to rule that out.

You could disconnect the vacuum line leading to the EGR valve (disabling it) to see if that makes a difference.

 

Hey, Thanks for the input. Yeah, I'm about ready to try anything at this point. I have three 1st Gen Tacoma's. I also have a 2003 and 2004. All have been setting up and have idle issues. The 03 and 04 have a steady high idle, even after warming up. A Yota Guru suggested running sea foam thru them. Possibly clean up the 02 sensors. Haven't tried that yet.
Once again, I appreciate the info and will give it a shot. Thanx, Ben

 

Typically, an EGR-related problem causes a rough idle, but still worth looking at.
If you haven't already, get it scanned for codes, even though you may not see the CEL light on.

It could also be a faulty coolant temp sensor, the one at the back of the head (hard to get at ).

No experience myself with your issue, just throwing out possibilities.