Hello,

I have '91 4Runner V6 2WD A/T. I guess it's a 2nd generation 4Runner...
I've read on this forum, that O/D doesn't kick in until the engine is hot. In my case, it takes 20-30 minutes of driving on the street before it fully warms up and the O/D kicks in. When I go on a highway it doesn't warm up to normal temperature at all!!!
When I finally warm it up on the street and get on the freeway my O/D turnes itself of as the engine cools down while driving 60-70 mph (no lights are flashing).

If I unplug the ENGINE TEMPERATURE SENSOR the O/D will work all the time (even the the car is cold), but there is only one problem...with the sensor unpluged it takes 5-6 tries before you can start the engine in the morning.

HELP!!!

 

I'll be the problem is a stuck thermostat. Change that (and the coolant while your at it) and your problem should be solved.

 

This is wierd, because my '91 4Runner's O/D worked all of the time. Even right after i started it.

 

Yup, thermostat.

 

It sounds like mtnfreak and Robinhood150 hit the nail on the head. That's going to be my guess too.

Good Luck

 

Thanks, I'll buy a new thermostat tomorrow!!!

I'll keep you guys posted.

 

Hey again,

As you've recomended, I went to a TOyota dialership and bought an original thermostat. When I've installed it I took my truck on the freeway. It was fine for the first couple of miles, but then my temperature went down again and O/D quit on me.

What else could be the problem?

P.S. I have an aftermarket engine temperature sensor (autozone) & a radiator fan from '88 Toyota Supra, but I had to take out fan shrouder ( I guess that's what you call it). It's a black peace of plastic that directs the air from the fan on the engine. So, I think that a bigger Supra's fan and no shrouder should cancel each other out and keep the temperature normal...?

Thanks

 

Well, you've eliminated one possible cause but added two more. Somehow, your engine is still getting too cool. My experiences tell me to blame anything from AutoZone, so I'd start my diagnosis
with the sensor.

 

Well, the engine might be getting up to temperature but the sensor might be sending a bad signal. My money is on a bad sensor now.

 

Well, I've thought of it too...but if the sensor is bad my check engine light should be on...? Do you think there could be a difference between Autozone sensor & the original one?

 

You should try changing the temp sensor. Could also be that the TPS is out of adjustment, but try the easier things first. I live in Canada and even I've heard of the "reliability" of Autozone parts.

 

I've almost forgot to mention...when I start my truck in the morning and drive it for a couple of miles, my temperature doesn't go up too much, but then I stop, shut off the engine, and start it back up, the temp is almost normal...what could it be?

 

Not necessarily. You have OBDI which basically sucks compared to OBDII IMO. If your sensor is putting out a bad signal but still within the specs for the sensor signal then it won't throw a code.

The Toyota sensor is much better. That is the difference. I'm going to agree with Robinhood150 and vote for the sensor too.

 

I had a similar problem on my Runner. There is a hose/tube that feeds a coolant temp sensor on the back of the motor (this senor is between the firewall and the plenum of our motor). The hose/tube runs from right behind the thermostat up to the sensor. This sensor is what controls the O/D. When I had my water pump replaced, the dealer didn't remove all of the black, rubbery gasket material and some of this found its way into that hose/tube and blocked it up. The truck would not shift into O/D when I first would run it because no hot coolant would make it to the sensor and thus the ECU thought that the truck hadn't warmed up enough to allow the trans to shift into O/D. But if I drove it and got the engine hot, then stopped and let it sit, the heat from the motor would 'soak' the sensor and the truck would shift into O/D until the fan blew air over the motor cooling it off thus causing it to drop out of O/D. I could watch the temp gauge and see it sit right at mid range and then as I drove watch it drop below that point and the truck would shift out of O/D. It was all because the hose was clogged and 'fresh' hot coolant wasn't flowing through the line and over the sensor. I had the dealer (because they had left the black material in the system) blow that hose/tube clear and the problem was fixed.

This sounds like your problem.

David

 

It sounds exactly like my problem...but I don't understand which hose/tube you are talking about??? DO you have a pic or a diagram by any chance?

 

Alex: I e-mailed you a website address (the first email bounced back):

http://www.net-impress.com/4runner/cd/

Pull up the 30l v6 v.pdf file and look on page 10......find the Coolant By-pass Outlet (item #6). This is what the tube attaches to. The tube then runs down to the back side of thermostat housing. The Outlet is also what the Temp Sensor I refer to above fits into.

Go look between the firewall and the Intake Manifold. Actually, this Outlet sit under the top of the Intake Manifold.

Hope this helps. (I e-mailed you this same message, but in order to help others in the future Searches on this Forum, I'm posting the same info here......)
David

 

Thank you. Had done it today...so far works like a magic!!!

 

Cool

 

Well, it was good while it last....

The problem still exists!!! But it's MUCH MUCH better than it was before I've cleaned the tube. Now the temperature drops just enough for the O/D to turn off and then warms back up in a couple of miles and then drops again (it happens on a freeway).

Please, need help!!!

 

You probably have additional junk floating around through your coolant system that is intermitantly clogging up the tube. Did you remove your thermostat and look to see if there was anything clogging the tube from that end. You'll see the tube inlet in the thermostat housing. Look at that. When I had my problem, I found that black gasket material that looked like artificial fishing worms hanging around the thermostat. You might want to get a coolant system power flush to try to get more of whatever is clogging you system out.

Hope this helps.

D