96 integra temperature needle reading low

[garlicbreadman]

Hi,

My friend purchased a 96 integra ls with 190k miles and one of the problems it has is that the temperature needle always reads at the C bar. I hooked up my obd2 scanner and notice that the coolant temperature was always around 140-150F, which is well below the normal cruising temp of around 180-190F. I am automatically suspecting a stuck open thermostat, however i am also suspecting it could be the EngineCoolantTemperature sensor that could be reading the temperatures wrong. Also, after driving the car for 20 minutes, the heat when full HOT doesnt get no where near as hot as my 2001 integra LS(hair dryer hot). Idle also seem to be on the high side of about 900-1000. Normal idle is 650-750.

Is there a way i can test the ECT so that if this part is faulty, I can purchase this part when i purchase the thermostat?

Thanks

 

[Quest]

Just buy a replacement thermostat (OE preferred, with OE temp spec, don't buy aftermarket ones with higher than OE temp spec.) and replace it.

temp reading low typically is a sign of either thermostat faulty(more common than you think) and/or thermo sensor faulty (remotely possible).

Q.

 

[Olas]

If the blowers aren't getting hot there could be air in the system, try and burp it.
Thermostat could be faulty, test it in a pan of boiling water.
Coolant temp sensor could be faulty, somewhere on the Internet you'll find factory data for the resistance of the sensor showing certain ohms at certain temps, test with that same pan of water and a meter.

But if you're going to all that trouble to pull and test stuff that already has wear and tear, you may as well put new parts in when you put it back together..

 

[ThirdeYe]

I can almost guarantee its the thermostat. If the temp goes down when you drive and up when its idling, its the thermostat. I had the same problem with mine. Its likely stuck open. BTW I used a Duralast thermostat from Autozone and had it in the car for 8 years and it was still functioning properly when I sold it.

 

[Quest]

typically, after so many years of thermocycling (what? 19yrs!?), thermostat will either becomes faulty or lazy, period.

This component plays a vital role in keeping the EFI engine in proper closed-loop operation. If it fails (opens), engine will run cold (open-loop) and all other issues follow. If it runs lazy, it will consume more fuel than normal but still get to work partially in closed-loop mode.

It's not that difficult to diagnose a faulty (opened) thermostat and once that's determined, I'd go right ahead and replace it w/o hesistation.

A lazy thermostat is another story. Only by means of swapping in a fresh new one would you be able to detect the diffference when it warms up to normal operating temp.

Also: 3rd scenario: I came across partially closed/opened thermostat before. Save this for another round of discussion.

Q.

 

[garlicbreadman]

Thanks all for your input. I will buy just the thermostat and hope the ECT sensor is good.

 

[SnowDrifter]

99% of the time it's the tstat. Usually temp sensors don't read funky like that through the OBDII port.

 

[Subdued]

thermostat is cheap and at 190k it might be good to replace regardless.

 

[Jim_Truett]

So the gauge is low, as well as the temp on the scan tool through the obd port. This is easy. The gauge uses a separate sensor for its readings. The ECU has its own ECT sensor. If both read low, then the probability of a bad thermostat is extremely high.

 

[Tegger]

Originally Posted By: garlicbreadman
I will buy just the thermostat and hope the ECT sensor is good.

You just reported that the heater output is poor. That ties the problem to the thermostat. Your ECT is surely just fine; they rarely go bad.

 

[garlicbreadman]

Thanks again, i feel confident changing the thermostat will resolve the issue now!

 

[Gokhan]

I had a stuck thermostat once. The engine would run ice-cold and sound strange on the freeway.

Always use an OEM thermostat. It's about $20 and the dealer should stock it. It should come with the O-ring, but if it doesn't, make sure to get a new one.

Also, when installing the thermostat, make sure that the jiggle valve is at the top.

 

[garlicbreadman]

Update:

Changed with OEM acura thermostat and now the needle is pegged right below the halfway point. Old one was stuck open i believe.

Here are the changes ive noticed by changing the thermostat:

Engine reaches full operating temps quicky(185-195F according to OBD2 reader)
Hot Heater air available quick!
Idle RPMs are now 650-750 rpms (perfect), was on the high-side of 800-900 before the change
Gas mileage should go up now? Havent driven it enough to see the difference.

Previous owner neglected maintenance on this car, the coolant was brown/green and smelled like fouled fish :\ Replaced 7 hoses that has coolant running through it and i put in some cool blue honda fluid.

 

[PandaBear]

One method I found that is very good at troubleshooting stuck open thermostat is to drive a long downhill route and see if the engine temp goes below normal. I found this on 2 of my car that would stay at normal temperature on flat road.