Won't Start When HOT, when cold runs great

Alright guys, first time the truck is really stumping me. 1995 3RZ

I noticed it would have a hard time keeping idle a few days ago (almost a week) but I would just blip the throttle at stop lights and all seemed well. That has slowly gotten worse and has died on me a few times at stop lights but I was able to restart it by holding the gas down. It only dies when idling-until today.

In an attempt to fix the problem I took the throttle body off and cleaned it, cleaned the IAC (Idle Air Control) valve, and put that back together Sunday. Idling seemed to be improved on cold starts it would be 1250-1500 RPM, then when warm it would go down to about 750-800 RPM. Perfect as far as I am aware.

Sunday after the above it still seemed to have a few issues and died on me in traffic a couple times. Since I had never put new O2 sensors in, I bought some new ones today and put them in, as well as cleaning the MAF sensor with MAF cleaner and not touching the sensor. I promptly put it all back together and drove about 2 miles, it died at about 1 mile but I was able to restart it and drive another mile when I went to park it and before I could turn it off it died. A half hour later I tried to start it for 25 minutes to no noticeable progress. Then got towed home.

-before getting towed we unplugged the battery then reconnected and started for a second then died.

@Ghost.

What are the tech wizards suggesting?

 

Oh and no codes, but I have previously had an intermittent P0420 code, catalytic converter issue

 

Already posted elsewhere but unplug your intake air temp sensor and give it a try. Common problem on old 3rz equipped tacos the sensor goes bad and the ecu get confused on what to do.

 

The one in the airbox? I tried unplugging the coolant temp sensor and that seemed to have a slight effect but not much.

 

That's the one, giver er a go. Many have said when it goes bad it feeds numbers that are massively wrong and the engine can't adjust timing and fuel far enough and it just poops out. It actually used that sensor a lot more than most for some reason.

 

Well it was worth a shot, tried cranking over for a few seconds with no attempt at starting. Didn't keep trying so I wouldn't piss off the neighbors.

 

Well since that didn't work I would start questioning the fuel system, specifically the pump.

 

You need to Replace the PCM Module, you have a internal cracked circuit board ! Very easy to do ! Then have rescanned and reflashed ! Update new PCM ! When cracked heat makes crack expand and separate, when cool shrinks back and contact is made! Buy a used or aftermarket one or OEM if in Great condition !

 

That's kind of what I'm thinking. So burnt out though lol.

 

Highly doubt this. I'd expect codes to from this.

 

This same thing happened to me with my 1999 Toyota Pickup ! Changed with a used good condition PCM and problem was solved!

 

You didn't have any computer codes? Mine will NOT even try to start now when cranking.

 

I'm wondering if there is an easy way to check for fuel pressure... Never done this before.

 

There are several ways to go about this.
(on a v6, principle same for the 4) For simple pressure/no pressure as in "is the fuel pump running?" pull the soft "fuel return" line and check for flow (be safe). It's the hose coming off the fuel pressure regulator. Be aware that the pump does not run until the engine is turning over and/or being cranked by the starter. If there is flow, pinch the hose shut. If the engine runs or attempts to run, the pressure regulator may be stuck or leaking. The engine will "run" sort of, or at least try to run with as little as 20-25 psi.

For an actual PSI reading you will need a fuel rail adapter like this fuel rail adapter (not positive on fit for the 4cyl) or a tee fitting cut into the fuel feed line and of course a pressure gauge with misc fittings to connect it.