Coolant temp sensor info needed

[T4Rscott]

Hey all,

Here’s my situation.

My 99 V6 has a high idle. I replaced the throttle body with another from a lower mileage rig.

I now feel like I’ve gone from the frying pan and into the fire, so to speak. Before it was idling at about 800 in park, and 675 in drive at a stop. Now it’s 1100 in park and 875ish in drive at a stop.

Now I’m starting to think the coolant temp sensor maybe the culprit. I don’t have a CEL illuminated.

So, can a coolant temperature sensor be faulty without turning on the CEL?

And before the question arises, yes I have checked for vacuum leaks and I did a reset on the ECU. Also the IAC and TPS are new as well and I swapped them to the newer unit.

I hope someone has some insight on this.

Thanks,
Scott

 

[Bad Luck]

Hey all,

Here’s my situation.

My 99 V6 has a high idle. I replaced the throttle body with another from a lower mileage rig.

I now feel like I’ve gone from the frying pan and into the fire, so to speak. Before it was idling at about 800 in park, and 675 in drive at a stop. Now it’s 1100 in park and 875ish in drive at a stop.

Now I’m starting to think the coolant temp sensor maybe the culprit. I don’t have a CEL illuminated.

So, can a coolant temperature sensor be faulty without turning on the CEL?

And before the question arises, yes I have checked for vacuum leaks and I did a reset on the ECU. Also the IAC and TPS are new as well and I swapped them to the newer unit.

I hope someone has some insight on this.

Thanks,
Scott

This should be what you’re looking for: https://www.toyota-4runner.org/832194-post3.html

That’s the one the ecm uses. The instrument cluster gauge uses another sensor toward the back of the driver side head.

Edit: easiest way to confirm if that’s your problem is to look at the intake air temp and coolant temp at cold start.

 

[T4Rscott]

Thanks for the help.

I’ll be checking the values today.

 

[T4Rscott]

This should be what you’re looking for: https://www.toyota-4runner.org/832194-post3.html

That’s the one the ecm uses. The instrument cluster gauge uses another sensor toward the back of the driver side head.

Edit: easiest way to confirm if that’s your problem is to look at the intake air temp and coolant temp at cold start.

My OBD reader only gives coolant temp.
It was reading 185 and the engine was a full temp

 

[Bad Luck]

My OBD reader only gives coolant temp.
It was reading 185 and the engine was a full temp

Was it reading close to ambient temp from a cold start?

 

[T4Rscott]

No, I noticed it was reading at about 75-80 when I started it up this morning. The outside temp was about 30-32 degrees.

I didn’t have the reader plugged in when I first started it. It had run for a couple of minutes before my reader finally came to life. The first temp I remember seeing was 77 degrees.

I ordered one from my dealer. It was only 45 bucks

 

[phattyduck]

My OBD reader only gives coolant temp.
It was reading 185 and the engine was a full temp

That's in the normal range for winter. Summer may be a few degrees higher.

I'd be checking for vacuum leaks at this point...

-Charlie

 

[19963.4lsr5]

For the record our 3.4 gets up to 150f pretty quick. I don’t know how long it took you to connect and look at engine temp but my rig went from 40f to 83f just idling in 2 minutes.


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[T4Rscott]

I did another test the other day and the intake temp and the coolant temps before starting were within a degree of each other.

Did more digging into my situation and found the stop for the vacuum assist to be set too high not allowing the throttle plate to close properly.

 

[brillo_76]

I did another test the other day and the intake temp and the coolant temps before starting were within a degree of each other.

Did more digging into my situation and found the stop for the vacuum assist to be set too high not allowing the throttle plate to close properly.

Maybe that is causing you ac not to work at idle?

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[gamefreakgc]

800 in park and 675 at idle is normal values. Mine is closer to 900 in park and 650 at idle in the winter, then like 700 in park and 550 at idle in the summer.

Still have the old throttle body?

 

[brillo_76]

800 in park and 675 at idle is normal values. Mine is closer to 900 in park and 650 at idle in the winter, then like 700 in park and 550 at idle in the summer.

Still have the old throttle body?

Mine idles closer to 500. 6 need to verify with torque pro. I just see my idle 550 range.

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[Endlessblockades]

No, I noticed it was reading at about 75-80 when I started it up this morning. The outside temp was about 30-32 degrees.

I didn’t have the reader plugged in when I first started it. It had run for a couple of minutes before my reader finally came to life. The first temp I remember seeing was 77 degrees.

I ordered one from my dealer. It was only 45 bucks

I've read on these pages that you want all readings to be pretty much the same at cold start. I took this photo yesterday AM because we're freezing balls down here in CA! :smow:

 

[T4Rscott]

800 in park and 675 at idle is normal values. Mine is closer to 900 in park and 650 at idle in the winter, then like 700 in park and 550 at idle in the summer.

Still have the old throttle body?

Yes, in fact, I put that back in yesterday.

 

[T4Rscott]

So I found both TBs to be binding a bit when closed.

Mine ended up being the 50 cent mod washer had the start of some corrosion ( gotta love Maine). I loosened the nut, slid the cable cams forward a bit and lubed them.

It now seems to drop to about 750ish at around 25 degrees.

I ended up putting my original TB back on, with the vacuum starting assist from the other as mine was leaking.

Now I have to check the adjustment on the aforementioned vacuum start assist to see if it’s too much or too little.