1990 Toyota 4Runner • 170 miles

It always stall when same conditions exist (engine hot, slowing down or idling at stop sign. (This can't be called intermittent problem)so why no code is recorded for this problem?

The very first time it occurred, I found the inlet hose connected to the throttle body was cracked. Replaced it and it worked fine for 2 weeks and then it kept on stalling.

Engine light works, reports other faults (disconnected O sensor, it was detected, error code was recorded and I was able to read the code from engine light)

Verified and adjusted idle speed (Cold start 1700, gradually rpm drops to 800 in park and 600 in Drive). Timing is set to 10.
PCV is has been a major suspect but the location makes it unreachable unless half parts under the hood are removed but I did heat up the engine and sprayed Throttle cleaner in the valve a few times with no results.

So far done the following:
Used Fuel Injector cleaner and it run fine for 60 miles before it stalled. Inspected all related hoses, cleaned air inlet path, Verified functionality for canister, Dash Pot, Pressure Regulator, EGR Modulator, VSVs and Check Valve per Toyota Shop repair manual instruction. Removed, cleaned and reinstalled Throttle body, Mass Airflow sensor, and EGR valve. Replaced Spark Plugs, Oxygen sensor and Catalytic Converter. Won't make it to the dealer (too far) so I took it to local auto repair shop. They replaced vacuum switch and also killed my battery in the process (total $350) and still problem exists. I have owned this truck for over 20 years and depend on it. Please help!
So far I have spent $787. If my problem is resolved I will most definitely donate to this site.
February 22, 2012.

Just an update. I reached my limit of spending ($1K) on the truck for now. The truck has officially been put in hibernation. Someday I will tow it to the dealership. In the meantime, I feel like a disabled person who has lost his wheelchair.

May 21, 2012.
I don't think smoke should have been visible. You might try seeing if the seals or gaskets around those 2 parts can be worked on and fixed.

May 21, 2012.
Out of hibernation and back on the road again!
As you all recall, my truck would always stall while idling at stop signs and stop lights.
Running out of options, I played around with Throttle control sensor to see if it would effect idle performance and hopefully stop the stall problem. This action recorded two engine faults.
A) Throttle Control Sensor Fault,
B) Engine Coolant Temperature Sensor Fault.

Set back Throttle sensor to original state and the error for this sensor went away but from here on, the Coolant temp sensor fault persistently remained. I replaced the Engine Coolant Temperature Sensor (ECT) and Halleluiah! I have driven it for 100 miles since and no stall and it passed California s strict smog test beautifully. After spending $1300 replacing and or cleaning many parts, a $13 sensor fixed the problem. For 8 months that I was dealing with stall problem, the truck neither generated an engine fault nor the temperature gauge indicated anything other than the normal driving temp until I messed with Throttle control sensor. How and Why? Well, at this point I don t care.
In any case, thanks to all those who made suggestions and recommendations.

Sep 8, 2012.
Hadia, congrats. California's smog laws are the strictest in the country.

As to why the ECT would be bad but not generate any spurious or incorrect readings or any codes, that's one of those things that Toyota isn't telling anyone.

Sep 9, 2012.