It's my friend's '92 4Runner again, long ago it was having a constant, mild occasional miss issue. You guys suggested a bottle of good fuel injector cleaner and it solved the problem. Rock on!

But now, every few stops @ stop signs, lights, etc. the vehicle idle will drop very low, below 500 (which appears to be normal idle to this vehicle), perhaps as low as 250-300 and feels like it's going to die. Step on the gas to take off and it's fine. Next stop it usually doesn't do it, behaves fine. It's random. Perhaps 1 out of every 3 or 4 stops it will do this. Kick it out of gear when the idle drops low and rough and it continues to do it. Drive to the next stop and it's fine. Repeat.

Any ideas? At last check TPS was fine, all intake tubing should be okay. It has approx. 180K on the clock. Head gasket has been replaced per recall long ago.

 

Sounds like the head gaskets are going bad again.

 

....or it could be the EGR valve sticking open.

 

I've had the same problem. Try cleaning the T-body. There is a small thermostat on the back of the T-body that regulates rpms at idle. Make sure it's all neat and clean.