OBD-I and Closed / Open Loop

Is there any way to prevent OBD-1 Toyota 4Runner 3VZ-E from going closed loop?

I have this 4Runners that I can get it to run very good even on snap throttle while is on open loop, As soon as it warms up it just dies.

If I could keep it running while is hot without going on closed loop I could try to read the ECU parameters and find out which one/s are causing the problem.

I would suspect that temperature sensors (AFM , EGR & Coolant sensors) but then it dies I can measure as quick as I can and do seem to be doing the job calling for closed loop.
I do not have access to OBD-1 Scanner.

Any ideas?
Thanks

Closed loop means that the Engine computer is listening to, and adjusting for, the Oxygen Sensor's feedback. I would start there. (Disconnecting the O2 sensor(s) should prevent closed loop? )

Tanks. I did try yesterday and removed the O2 sensor (Only one on this car, not California car) and it doing the same thing.
Quit after it got warm on idle.
Very responsive to throttle or snaps while warming up. I wish i could be able to read all what the ECU is getting but I give up.
Today the car goes to his owner across the street together wit my feelings failing to understand what is going on.
I have work on this car for almost 5 months on and off, getting no really ahead on the game.
Time to give up.in Excellent mechanical conditions with almost everything replaced(ashamed to admit that on this forum)
Will go to Craigslist in Austin-Texas or to the scrap yard. The owner cannot afford any other repair bill. I myself footed the some of the bills in hopes to help him.
Thanks to all on this board that have devoted their time with suggestions and their knowledge.
It is time for me to accept defeat. At least i purchased Pico 2205 and learned a bit about its use.
Thanks to all.
As a closing kind of unusual notes, I am attaching a pic for curiosity of my very first car, a FORD Model "T" 1925 purchased in 1958 when I was 18 years old.

One quick test I'd try is removing the vacuum line at the EGR valve and plugging it. Some 'yota EGR systems are electrically enabled but vacuum controlled. Could be PCM is enabling EGR when the truck gets up to temperature then a fault with the vacuum control is pulling the EGR valve wide open.

Batiscafo wrote: i purchased Pico 2205 and learned a bit about its use.

I wish i could be able to read all what the ECU is getting

If you have an oscilloscope, you can.

If the car is just across the street, I would get it back and, in addition to Matt T's suggestion, I would scope the O2 signal. I'm not sure what voltage range Toyota operates at (Anyone?) but, it should oscillate, up and down, close to one volt. Voltage will go HIGH when the exhaust RICH, and LOW when the exhaust is lean.

Disconnect the sensor and read the voltage on the signal wire. As I said, I'm not sure what voltage Toyota operates at, but many systems will operate on a 450mV bias. Others operate on a higher voltage. Either way, this voltage is pulled UP and DOWN, based on oxygen content of the exhaust . If you back-probe the signal wire, you should be able to watch this with your scope (reconnect the sensor). You can, also, manipulate this signal with a test-light. Connect the test-light to battery POSITIVE, touch the signal wire. The voltage should increase to battery voltage. Connect the test-light to battery NEGATIVE and touch the signal wire. The voltage should decrease to ground. The fuel trim/engine should respond to manipulation. If you can't manipulate the signal voltage with a test-light in this fashion, then there is a problem with the signal wire. I'm may be SHORTED. Or, it may be OPEN.

Nice quotes