2000 2.4 Taco stalls only in warm weather.. Help!

Title pretty much sums up the problem. It runs and drives fine if the outside temp is below about 70*F, but once it gets above that, it will stall whenever you try to accelerate from a stop or slow roll. It always starts right back up after it stalls too.

It still idles fine and comes to a stop without stalling, but once you try to accelerate it stalls and it does it every time. It also seems to only stall when it goes into closed loop mode after the engine is warm. Even if its real hot outside, if the engine is cool, it wont stall until it warms up.

Thinking about unplugging the O2 sensor to force open loop all the time and see what it does. Also, not sure if this is normal but unplugging the MAF while it's idling will cause it to die. Runs worse with MAF unplugged also.

The truck is all stock, automatic 2.4L, year 2000 and has 580,000 miles on it! Any other ideas I can try to figure out whats causing this?? Thanks!

Ryan

 

Disconnect the vacuum line to the egr and try it.

 

Just went out and tried that. Didn't change anything. I should also mention that it only stalls under load. When in park or neutral the engine will rev freely without problems.

 

yes the MAF needs to be in the loop. try cleaning the MAF sensor with MAF sensor cleaner. make sure you disconnect the batt before hand

 

Do you know how to check the TPS with an ohm meter?

 

It's a common issue for the 2rz, but they usually don't start getting it until 850-900 thousand miles. I think you got a lemon, take it back

I have no idea but closing in on 600k is pretty damn cool!

 

I would if you told me how . I do have a cheap harbor freight multi meter.

 

The TPS is nothing more than variable resistor kind of like a volume control on a radio. Put your meter on ohms connect it to the center pin with one lead and the other on one to one of the other pins. The resistance readings are not as important as how well it changes it cannot drop out even slightly the readings must be smooth not jumpy at all. I don’t know how your throttle works on your truck if it’s a fly by wire you’ll have to remove the TPS and turn it with a screw driver. If there is a glitch it very well could be your problem because it sees no throttle position. FI repairs can get expensive fast if you just throw parts at it until it runs right.

 

Ok just tried doing that, and the resistance seem'd to be pretty smooth. With the dial on the "20k" ohm setting, it went from 3.3 closed throttle down to .86 at full throttle IIRC with no drops or glitches in between. Unplugged the front O2 sensor (before cat, trying to force open loop) and unhooked the battery for a couple mins, but that didn't change anything either.

After filling up with fuel, it runs MUCH better but you can still feel it hesitate when you give it gas from a stop, but it wont die. So so far these conditions have to be met in order for it to die when accelerating from a stop:

1. Warm weather (above 75-80)
2. Engine up to operating temp
3. 3/4 or less tank of gas

If any one of those conditions aren't met, it will run fine. However it's not hard to meet all those conditions, so it still happens quite often.

Is there a way to check the fuel pressure on the 2RZ? I looked but couldn't find a Schrader valve like most FI cars have on the fuel rail to connect to. Am I missing it or is there somewhere else to measure it from? I'm starting to think maybe fuel pump or MAF. I replaced the fuel filter last year, so that should be good still.

Thanks for all the help and suggestions so far though!
Ryan

 

I don't believe you can force a open loop just by unplugging the O2 sensor. I can't tell you if your's has no test port or not but many required a banjo fitting adapter to check fuel pressure. Improper fuel pressure can have an effect on a MAF sensor they are not easy to test there are too many parameters, the easiest is voltage output (0-5 volts) and visual inspection. Depending on contamination it can either be to hot or too cold either can cause issues.

 

This is just a wag (wild ass guess), but it could be related to the vapor recovery system (since the fuel level is one of the conditions).

See what happens when all 3 conditions are met, and you remove the gas cap.

 

Im having similar problem,

in cold works great ... but once warm, if you turn it off, it will not start again.

and if you just continue on... after 35 mins of driving or just kept in idle ... it will turn off automatically.

I have changed, coils, cables, sensors, maf, airfilter, now im going to change the fuel pressure regulator and fuel pump.

Just ordered a fuel pressure tester, im reading that the tacomas dont have fuel pressure test port btw.