Haven't seen a thread on this particular, oh no here we go, idle issue! 1990 4runner 22re rebuild new TPS, timed per Toyota requirements, idle rpm 850, AFM tests out good, O2 tests out good, injectors are working (don't know flow rates), new distributor cap, new rotor and new wires.
Now the problem, when let off on the accelerator the rpm drops down in the 250 - 300 rpm range rattles around and slowly works it way back up to level out at 850 rpm. Any idea what would cause the large drop and slow increase back to set rpm value??
Would pull my hair out, but I don't have any, LOL!!

 

I'd double check the TPS. A major purpose of the TPS is to warn the ECU of large throttle changes and consequent upcoming air flow changes, so that the ECU can stay ahead of things instead of being purely reactive. It allows the ECU to duplicate the functions of the accelerator pump and throttle dashpot on carb'd engines , although with considerably more precision and sophistication.

 

^^^^^ What he said


Also check EGR system it may be sticking open some.

 

http://www.4crawler.com/4x4/CheapTricks/TPS/index.shtml

 

Mine did this for a while, then I realized I had to open my throttle screw to about halfway instead of 1/3. No problems since!