Hello all,

I just got a '89 3.0L automatic and the overdrive is not functioning right. It goes in and out at highway speeds (65 mph). Mostly it does not engage at all and it hums along at about 3200 rpm at 65 mph. But occasionally it will just click in, for no apparent reason, and the rpm's will drop down to about 2400. then a few miles down the road it will just click out again and the rpms will go back up. There doesn't appear to be anything special that makes it click in and out, it seems pretty random.

I took it to my mechanic, they thought they fixed it, but it still functions the same as before. Any help would be much appreciated, I'm at a loss and nervous about what the mechanic is going to tell me. Thanks-

 

A thermostat stuck open can cause this problem. My thermostat was stuck partially open causing a very long delay when initially going into O/D, then when it was warmed up it would somtimes kick out if the coolant temp got cool enough.

If the thermostat is ok, the engine cooland temp sensor could be the culprit. It is easy to check with an ohmmeter. The resistance will vary on the sensor depending on the temperature. There is a graph available for the acceptable resistance output.

 

A bad cruise control ecu can also cause this problem. It takes about 2seconds to figurre out if its the problem. It's in the driverside under the kick panel with the fuse block...pull the plug, and go for a ride.

 

thanks for the info, I will check these out-

 

Don't mean to hijack this thread but I seem to have possibly the same issue. Takes me about 2-2.5 miles for my 95 3.0 auto to go into overdrive. Cruise control is worthless, it downshifts at the slightest hill and sometimes even on flat road. Also it will not upshift 9 out of 10 times when back on flat road.

 

There is a temp sending unit on the back of the intake(there is 3) that controls the transmission. I think it is the one on the drivers side or the middle. It will be the hardest one to get to for sure. You may also have low fluid in either the transfer case or tranny that will cause it to flutter. Mine sat for a few years and I had to install an external filter and flush it twice before it started shifting at all into OD, I changed the thermostat, with no results, then the sensor, then it worked fine. I had to go to Toyota to get the proper wiring diagram for the sensors, and to get the sensor (37 bucks).

 

I was a quart low last week on tranny oil and added a quart, I was thinking about getting it flushed but I've read some bad stories on getting them flushed. The sensors you speak about are you talking about the cruise control issues?

 

When I say flush I mean I dropped the pan and filter, installed new filter and gasket, fluid and an external canister filter, ran the crud out of it, dropped the canister filter and changed for a new one, drained and replaced the fluid and repeat 1 more time. This was for the Overdrive issue.

 

You should start your own thread.

 

Just for drill, could you please describe what this one looks like? I found the black box for the antenae relay, and near that is a blue box. Am I close?.....

('91 4Runner, 3.0, A340H, 182k miles, all stock except for the 31" BFG's. Which I think may be part of the problem)

 

I know this is an old thread but this is what fixed mine.
https://www.yotatech.com/forums/f116.../#post51731766