Burning reach until it get hot. - 3VZE The dies.

1995 A/T 2X 3VZ-E
Starts Ok when cold and idle is reasonable.
Once hot quits on hie own
Pull all plugs (less than 5 Months old) and full of carbon not burnt.

Questions:
The temperature sensor Volts at ECM was a little off, but the panel temp. indicator seems to be warming up as it should and goes as always did to the middle.

First: Does the ECU reads from another sensor or uses a tween sensor in the same body?
I bought a new one and has to terminals. I am lost, also cannot figure out how to reach there.

Second: could it be the AFM temperature sensor that keeps the fuel mixture really off:. Is it possible to just fake the temperatures to see of the problem is there and save the trouble to change the coolant sensor?

I will try now to scope the two signals to the ECM but I have no idea of what will be a good waveform.Look at youtube but found some on just MAF sensors. Anyone with a pointing direction to this?
Thanks

 

Get a hold of the Factory Service Manuals and read about how this OBD-1 monster actually works. There is a seperate temperature probe that is sending signal to the ECM and this is what tells the ECM to transition from going open loop to closed loop when the engine is warmed up. The temperature gauge has its own sender as well and they are not the same but share mounting locations on the rear coolant manifold on the 3.0L V6 3VZ-E. It is a separate manifold that is behind and slightly under the plenum and is smacked up against the fire wall. These connectors to these sensors will be brittle and prone to breaking with very little force, so beware!

The AFM is not like a typical OBD-II mass air flow sensor. The AFM's flapper triggers a set of switches and a rheostat that works in conjunction with the TPS at the throttle body. The AFM also has an air temperature sensor that is located in the inlet port to the flapper. Again an FSM read on this will help a lot in diagnosing the problem with it dying when warmed up. Two other components you need to check would be the knock sensor a single wire comes from this piezoelectric sensor and goes to the ECM for signal on allowing the advance and/or retarding of the ignition timing. The other closed loop item is the O2 sensor in the exhaust. It is not a wide band unit but does impact running when the the ECM goes closed loop. When its cold and at WOT the ECM uses fueling and ignition algorithms to time and fuel the engine. Otherwise when the ECM goes to closed loop operation it will be using the AFM, TPS, Distributor sensing coils in the bottom of the unit, the temperature sensor, the Knock sensor and the O2 sensor to fuel and time the engine.

Is the check engine light illuminated? If it isn't many of these things may not be functioning and no light will be shown so a DVM is your best tool for understanding what is working and what is no i.e connections and vacuum leaks are key suspects.

Is the pressure regulator on the fuel rail getting vacuum signal from the plenum? It would be good to thread a banjo for a fuel pressure gage to monitor the fuel pressure.

 

atgparker: Thanks for your input. I have been trying to measure those voltages and resistances, but I come to a big problem when trying to focus on so many parameters. It is old age that works relentlessness and frustrates me. It also takes ages to do checks that I forget what I just checked one minute ago.
I think I covered al vacuum leaks already and I just need to try until I find the parameters that are not in line with the specs.

I suspect that I15 connector is the problem since everything that is filing or brought MIL light goes thru it.BUt I search and search and cannot physically find it.
NO MIL lights for a while, just will do a few volt checks cold and then see what if seems when hot.

Thanks a lot for your suggestions.

 

[QUOTE="atgparker, post: ....................and vacuum leaks are key suspects.

Is the pressure regulator on the fuel rail getting vacuum signal from the plenum? It would be good to thread a banjo for a fuel pressure gage to monitor the fuel pressure.[/QUOTE]

fuel pressure is right on 39 psi and without regulator 45 psi. I had a pressure gauge almost for a month ON all the time.

 

The 3VZ-E specification for fuel rail pressure is a function of:

• The delivery from the fuel pump that is inside the fuel tank.
• A clean and unobstructed fuel filter.
• The dampener at the inlet to the fuel rail (prone to fail and push gasoline fumes into the cabin air vent under the bonnet)
• The pressure regulator near the oil cap.
• The assumption that the injectors are not leaking which includes the cold start injector that is located in the plenum.

Fuel pressure fluctuates as the throttle is opened and closed but it is < 6 psi and the FSM spec is 38-44 PSI at the fuel rail. So that checks out as OK.

If its dying when its warmed up its transitioning to closed loop mode and my first bet is the knock sensor is busted or the wire is broken where it passes between the head and a small opening in the intake manifold. The TPS may be out of adjustment or the O2 is bad or open circuit due to a corroded/broken connection but I don't think they would cause it to stall. Or the AFM is toast. This system is complicated and the FSM has a great section on the check engine codes and what the ECM can diagnose to cause illumination. The signals to the ECM have to include a voltage drop in the wires to transport the signal to the ECM. But if corrosion or some other physical damage has occured the signal may not be able to reliably get to the ECM. This is where back probing at the ECM's terminals can be useful to see if the signal is present.

Make sure the ground wires that are attached to the engine are clean with solid connections to the body as well as the battery to the block and body. I replaced and upgraded mine to remove this from the equation.

• DS head to inner fender panel near ignitor/coil (dielectric grease is put on all exposed metal of ring terminals before securing with OEM washer faced machine screws that are M6 for the most part)
• Back of Plenum to firewall (removed service disconnect plug and made a single wire to the fire wall with new wire, ring terminals and more grease).
• PS block ring terminal under bolt on bracket for AC-compressor to battery negative. (shined it up and greased it when engine went back into the chassis).
• Battery negative to inner fender panel close to fuze block molded plastic housing. (replaced battery terminals and this wire to the fender panel)
• AGM batteries are nice to go with as the battery acid is a gel and cannot capillary up along and corrode the battery terminals.

Electrons only move on the surfaces of conductors not inside the copper. So non-shiney wire or corroded looking terminals are not going to conduct well and will create a bigger voltage drop and that will stifle signal level voltages which are 0-5 volts for TTL switching as an example. Add a bit of heat to the situation and the conductors resistance increases. So, if you have something that is right on the threshold of not working when you add the heat-load from the engine compartment it will not conduct enough after it is heat soaked and in your case the engine dies.

For the most part Toyota has taken very good care in trying to forsake the time honored disruption caused by oxidation of electrical connectors and components which is a testament to the reliability they are renowned for. But many 3VZ-E's and 22RE's are pushing 30 years in age and for some they are in worse environments with real four seasonal changes unlike that of Southern California for example that is a pristine place for elevating the life of a vehicle. But even as dry as it is in desert like climates, oxidation still is going to happen just more slowly. So it is all relative to location, age and the general care or neglect that the vehicle has been subjected too.

The same can be said for a lot of the pneumatic circuits which adorn this OBD-I era vehicle. I put small spring clamps on most all of the original rubber vacuum lines that are everywhere on the 3VZ-E. Some were split so those are replaced and clamped just the same. That PS fender is an ocean of VSV's and BSV's that switch the EGR, the PAIR, boosts engine speed for steering while not rolling, as well as the AC and even connects the long side front axle through the ADD all of which is vacuum actuated.

I have said this before diagnosing this beast is fun if you have an Engineering Degree but can be overwhelming for those who are less well trained in the many disciplines that were used to design and manufacture these 1990-1995 vehicles.

 

AtgParker: I really agree and feel that maybe more than one of the items you mentioned are the cause of my nightmare.
And I thank you from the bottom of my heart for all the time and good advice you are providing.
But, and here is the but: I need to recognize that more than six month working on the car of my neighbor not only for free but buying myself some of the parts I replaced because I know his financial situation; is more than I can handle.
I have been checking voltages and resistances until the cows come home as you said, and part of the problem not attributed to the car is that I am closing into the 82's. Never been a car mechanic but I have always fixed/maintained my cars since my first car: a FORD mode T 1925 to my present 3 cars: Passat 2003,Silverado 1500 1998 and Civic 1997.
It has become every day more difficult to focus, to remember what values I read 15 seconds ago or what the heck was that I was doing.
I think it is time for me to admit defeat as much as I hate it, even ashamed that I have a BS in Mechanical Engineering I always felt it was nothing that I could not do, if others can do it and I was given enough time.

Today, a sad day the car is going across the street and he will try to sale it on Craigslist. On more test I will do is the "Test Mode" as suggested by someone yesterday I cannot remember where. Using T2 and E1 jumped for enhanced diagnostics. I did one run yesterday and as always the engine run well, no misses, no lights. But It may take more than one "Trip" to pop up the light.
I have to admit defeat, and just give my elder neighbor when he needs it.
Sometimes I have thought of buying the car from him until I can fix it, many priorities with the family have been pushed to a second level just to work on this car almost like a blind person without stick and limping.
I need to sincerely thank all the people that have taken the time as you did, to help me even that most of the time thy have seen that I was almost like a lost case.
I never posted anything because it would only be armchair thinking and would run other people on the incorrect path.
But I appreciate those on those on this and other forums trying to understand what I meant, and make sense of sometimes meaningless question. Got also good chuckles and learning many times reading the bottom quotes of seasoned people not only in life but also on the profession.
Thanks atgParker, you as well as other on this board ,have done a wonderful job at opening some path for soles that are kind of on the clouds.
I am posting a curiosity, a pic of my first car in Montevideo-Uruguay. Ford Model T 1925 that I bought when I was 18 from a chicken coup and myself re-bored the block to fit scrapyard Ford Model A 1931 using eccentric bushings at the piston main pin to accommodate longer old "T" connecting rods.

Thanks to all,
Wilson (Fermin is the distressed owner)