So my 2000 CE ( 144k) started having the 'poor cold idle and acceleration' problem. Found its usually due to either
1)dirty MAF sensor
2)coked up/dirty Idle air control valve or throttle body
3) Leaking Intake Manifold gasket.
I sprayed some carb cleaner around the intake manifold when the car was idling. No change, so gasket is still good.
I worked in the order of ease, first cleaned out the throttle body and plate. No difference
Next, I cleaned the MAF sensor with throttle body cleaner ( yes, you CAN use throttle body cleaner on these, as they are hot wire, not hot film. Still bad idle.
Next, I installed a brande new MAF sensor. Still bad idle.
Next, I removed the throttle body and cleaned it very well. I also removed the 4 incredibly stubborn phillips screws holding the IAC valve on ( to change the coolant gasket and clean the IAC valve better. Yes is was incredibly dirty in there, and the plate was hard to move. Those 4 screws were impossible for me to get off! I soaked them in PB blaster, and used a bit of heat from a butane torch. I was forced to bring them into my mech who used air tool, and still 2 of the screws broke off. After reassembly w/clean as a whistle IAC valve and coolant gasket. The bad
idle seems to be fixed, but now the acceleration is very stumbling even when the engine is warmed up.
BTW why Toyota chooses to design their IAC valve so coolant goes through it is beyond me. I did read in a blog somewhere that the design 'increases efficiencey'.
Don't know why.
I'll have to also note due to my stupidity, i removed the nut holding the throttle cable guide on the throttle body, as I thought i'd have to remove it since I couldn't get the throttle cables off the plastic guide bracket. It seems a previous owner or mech used silicone or glue on the metal cylinder ends to hold the cables in place
I finally used alot of force and got both cables removed, but forgot i had removed the nut so the the plastic guide fell off, along with the 2 springs.
It turns out these 2 springs are very difficult to reinstall properly, as one of them holds the throttle plate open just a little bit on idle. I couldnt find any diagrams to put the springs back on, so i just 'guessed' their correct installation, which would hold the throttle place shut and provide enough tension to close the plate.
I also replaced the intake manifold gasket anyway, since I had everything else off, and i've read this model gasket start leaking air anyways
After I got everything back together, including new throttle body gasket. The car is even worse than before. So i gave up and took it into my mech, who tried over 30 mins to diagnose it, but couldn't. He said i should just get a new throttle body at a junkyard and put that in, because of the springs being calibrated incorrectly, which he couldn't do, only the dealer, who would probably charge at least $600 for new throttle body. So now i'll have a dirty throttle body again, but hopefully the car will be idling correctly again.
If someone has the diagrams or service manual pages on the correct procedure to re-installed the throttle cable guide bracket and springs, i'd much appreciate it.