Temp Gauge Jumping up and down...Please Help

[Running4life]

My temp gauge in the dash is jumping up and down. It only goes from normal to cold. It does not jump to the High position and the Runner does not overheat. Sometimes it responds based on throttle position, sometimes it just jumps around at a constant speed/throttle position. When the vehicle is cold it will show cold and come up to normal operating range but then starts the jumping. I have googled it and believe it could be the sensor in the engine bay but don't know where it is. Does anyone have pics or can explain to me where it is so I can see if the wires are loose?
Thanks in advance.
BTW the vehicle has 147K on it and the timing belt,etc was done at 92K.

 

[Running4life]

Wow, plenty of views and no one responded... I found the sensor last night. Unplugged it cleaned it out and plugged it back in. No jumping this morning. Just for information it is a wire connection located on the front of the engine where the top radiator hose feeds into the thermostat. The connector was grey with 2 wires.

 

[jeanette]

Temp gauge bouncing up and down

I have the same problem of temp gauge bouncing up and down. Took my 99 4 Runner for a diagnostic test. Had a wire loose. This corrected my problem. Then just yesterday I noticed it doing it again. After reading your post about it being a wire by the radiator. That makes since since just a week or so again I had a hose loose at the far back of the motor...I'll definitely check it out. Thank you so much for posting this problem...Oh by the way, Ive had this truck since 2004. Had 71,000 miles on it. Now we're on our 2nd motor. 1st one had over 350,000 on it and this motor has 120,000 on it...Body is perfect!

 

[rubymac]

I'm having the same problem! I'm on a cross country road trip, and it was kind of freaking me out. After banging on my dash, it worked again for a bit...... but then went back to bouncing rapidly between where it usually sits and dead cold. My heater still works, and I haven't over heated yet, so I'm pretty sure the thermostat is still working properly when this happens? Right? I hope.

I just bought this 2000 4runner a couple months ago.
I had the timing belt, water pump, radiator and thermostat replaces when I got it.
Maybe they knocked some wires around?

I'm a total noob..... so I kept looking for the thermostat, but couldn't find it.
After checking the manual, it looks like it's near the lower radiator hose between the engine?
I think I might have to look from underneath, not above? Am I correct?
I'm going to try to wiggle those wire tomorrow before I get on the road again.

 

[baja1]

Wow, plenty of views and no one responded... I found the sensor last night. Unplugged it cleaned it out and plugged it back in. No jumping this morning. Just for information it is a wire connection located on the front of the engine where the top radiator hose feeds into the thermostat. The connector was grey with 2 wires.

it was my understanding that although that is the temp sensor in front the temp gauge is that hidden almost impossible single wire connector on the back of the engine at the firewall?

 

[Buckaroo]

Had this same issue - gauge temp fluctuations. There are two temp sensors - the one in the front of the engine (two wire) that provides temp data to the ECU and the one wire unit on the top of the engine in the back close to the firewall that feeds the dash temp gauge. Issues with the sensor feeding the gauge will not impact the computer control of the engine but it is annoying and inability to visually monitor engine temp in case of an issue is problematic. The good news, however, is that problems with this temp sensor won't affect your drivability so no need to panic.

There is a tab that is riveted on the gauge sensor to which the single wire spade electrical terminal connects. In my case, the rivet was loose and that was causing the gauge to fall out periodically. Replaced the sensor and it fixed the issue although finding the sensor was difficult - it is in the rear center of the engine on top. This is the sensor I installed....

https://www.amazon.com/gp/product/B000CB0AFC/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1

Buckaroo

 

[Caleb M.]

Mine is doing something really similar except it is going on the hot side. I don’t think it is actually getting hot because when I accelerate it goes back to regular temp immediately. There is no way the engine temp can fluctuate that fast and the car drives fine. It’s just started happening and I haven’t driven it more than a few miles since because I had an 01 tundra that blew the water pump and messed up the radiator,
I knew that one had a busted water pump tho.
Truck is a 1995 4Runner v6 w/ 137,000 miles Tia

 

[pluton]

p the radiator,

Truck is a 1995 4Runner v6 w/ 137,000 miles Tia

You'll have better luck in the 2nd gen 4Runner forum...this is the 3rd gen forum...'96-'02...the engines are completely different after '95.

 

[pluton]

Truck is a 1995 4Runner v6 w/ 137,000 miles Tia

You'll have better luck in the Classic (1st/2nd gen) 4Runner forum...this is the 3rd gen forum...'96-'02...the engines are completely different after '95.