AT shifting in/out of overdrive at operating temp? SOLVED
09-14-2016, 12:37 PM
#41
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What is the red circled one
Green circle below is the engine coolant temperature sensor. Note that this view is from the back of the engine.
what sensor is circled in red
The engine coolant temp sensor can cause the transmission to kick in/out of overdrive at operating temp if it's out of spec. I'd recommend testing it referencing the chart in my original post. The throttle position sensor is part of this same circuit and can cause the same problem, so I'd recommend testing that as well. http://www.4crawler.com/4x4/CheapTri...ml#AliveOrDead
As far as the engine taking a while to heat up goes, the 3VZ seems to be kind of cold blooded, at least mine has been since I bought it in 2004. Not sure why running the heater is causing your engine to warm up faster...typically this has the opposite affect as the heater core dissipates heat from the coolant thus taking longer to reach operating temp. One theory is that the coolant loses enough heat when running through the heater core during the first few minutes that when it hits the thermostat it closes it, disabling the cooling system and allowing the engine to reach operating temperature faster. Based on the info you've provided, it sounds like your thermostat doesn't have a jiggle valve/air bypass hole and/or is a single stage thermostat. Here's some reading on that subject (it's about the 22RE but same concept):
http://www.4crawler.com/4x4/CheapTri...tml#Thermostat
I'd test the engine coolant temp and throttle position sensors first (relatively easy to do and you can then rule them out), and make sure you have an OEM two-stage thermostat from Toyota.
Hope this helps and let us know how it goes!
what sensor is circled in red The engine coolant temp sensor can cause the transmission to kick in/out of overdrive at operating temp if it's out of spec. I'd recommend testing it referencing the chart in my original post. The throttle position sensor is part of this same circuit and can cause the same problem, so I'd recommend testing that as well. http://www.4crawler.com/4x4/CheapTri...ml#AliveOrDead
As far as the engine taking a while to heat up goes, the 3VZ seems to be kind of cold blooded, at least mine has been since I bought it in 2004. Not sure why running the heater is causing your engine to warm up faster...typically this has the opposite affect as the heater core dissipates heat from the coolant thus taking longer to reach operating temp. One theory is that the coolant loses enough heat when running through the heater core during the first few minutes that when it hits the thermostat it closes it, disabling the cooling system and allowing the engine to reach operating temperature faster. Based on the info you've provided, it sounds like your thermostat doesn't have a jiggle valve/air bypass hole and/or is a single stage thermostat. Here's some reading on that subject (it's about the 22RE but same concept):
http://www.4crawler.com/4x4/CheapTri...tml#Thermostat
I'd test the engine coolant temp and throttle position sensors first (relatively easy to do and you can then rule them out), and make sure you have an OEM two-stage thermostat from Toyota.
Hope this helps and let us know how it goes!
04-06-2017, 08:34 AM
#42
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Excellent thread! I'm having a similar issue with my new '88 V6 with A340H, except mine seems to shift into overdrive EARLY, almost skipping 3rd all together (can't tell for sure yet). Is there a temperature related condition that would cause the transmission to stay in overdrive? I also have been having some cooling issues (water pump leaks and coolant temp rises up a bit when I'm stopped and idling in traffic). I also noticed the cruise control cable is broken, and there is no light that illuminates when I press the overdrive button on the gear shift handle. I also typically drive the truck with the POWER mode selected with the ECT button on the shifter surround plastic frame.
06-25-2017, 08:12 AM
#43
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Great thread!
Wow, I wish I had found this thread six months ago! I have a 1991 4Rr 3.0.
I had the same issues, my transmission either would not shift into overdrive after it was warm or it would intermittently shift in shift out on the highway. I did follow this thread quite thoroughly and I changed my Coolant Temperature Sensor, did exactly what you said happen to you, worked for a little bit and then back to the same old song and dance. So then I went to my Throttle Position Sensor, I just removed it and tested it on my kitchen table. Everything was within spec so it was just a matter of adjustment. So I put it back on and used my multimeter to test it in different positions while it was attached to the throttle-body. Once it was in spec I took it for a drive, worked like a charm! My Coolant Temp Sensor broke apart when I removed it just as yours had. Obviously needed replacement. Probably from the heat over the years. I am going work my way through the rest of the circuit anyways just because of the ECT sensors condition. Thanks for you time, I'm truly greatful!
Shaun
I had the same issues, my transmission either would not shift into overdrive after it was warm or it would intermittently shift in shift out on the highway. I did follow this thread quite thoroughly and I changed my Coolant Temperature Sensor, did exactly what you said happen to you, worked for a little bit and then back to the same old song and dance. So then I went to my Throttle Position Sensor, I just removed it and tested it on my kitchen table. Everything was within spec so it was just a matter of adjustment. So I put it back on and used my multimeter to test it in different positions while it was attached to the throttle-body. Once it was in spec I took it for a drive, worked like a charm! My Coolant Temp Sensor broke apart when I removed it just as yours had. Obviously needed replacement. Probably from the heat over the years. I am going work my way through the rest of the circuit anyways just because of the ECT sensors condition. Thanks for you time, I'm truly greatful!
Shaun
Last edited by ShaunKris; 06-25-2017 at 08:16 AM.
07-09-2017, 08:10 AM
#44
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O/d out not working
I have already solved this problem but now I'm trying to pull haul stuff and my o/d off does not work at all. The button on the shifter clicks like it's suppose to but I get no light and when I'm driving and o/d is in the off position it still goes into o/d any ideas about what I should be checking????
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