Rep Power: 0

96 Civic CX trying to diagnose "cold bloodedness" problem. Slow to heat up, poor gas mileage around town (highway OK), long idle period with heater on will drop coolant temperature (in air temps below 20 deg F).

Changed thermostat twice now. First was good quality aftermarket, last (recent) was a genuine Honda 180 degree stat. No eng fault codes.

Question at hand is, does the OBD2 port allow reading coolant temperature on the 96 Civic? (Considering getting a scanner if I can read temp).

Thanks in advance.

Chuck

 
Rep Power: 518

Sounds absolutely normal to me. When it gets really cold, the heater can remove engine heat faster than the engine can make heat......

You waste fuel whenever you let the car sit and idle, and all that fuel that's burned without moving is bringing down your gas mileage

Obd2 data will give coolant temp among other data

 
Rep Power: 0

Didn't have these problems the first 15 years of the car's life. By idling, I mean when I am stopped and waiting for something or someone (e.g. 100 car train). I never warm up by idling, only by driving.

Some of the scanner manufacturers caution that any particular manufacturer may not implement any specific sensor inquiry and that early (e.g. 1996) cars usually have incomplete OBD compliance. If you are certain that the 96 Civic does implement the coolant temperature inquiry then I will go that route in an attempt to see what is going on.

Thanks for you reply, I appreciate it.

 
Rep Power: 518

ECT is one of several parameters mandated by the OBD2 standards, every OBD2 compliant vehicle should be able to display it on a capable scanner.
So are fuel trims, VSS, and several others.
Scanner capability may be another matter...try before you buy? Check reviews?

My own 2012 Civic can cool right down just by running the heater fan full blast....I can go from 180 to 130 or less in a matter of several minutes if I only let it idle in the cold. If I want it to get warmer and put heat out of the heater, I have to rev up the engine and hold it there for a while.

Gotta burn more fuel to get more heat.

 
Rep Power: 0

Followup:

Yes you can read coolant temperature via the ODB2 port on the 96 Civic. A large amount of interesting data is also available.

In my quest to solve this problem I found out that the coolant thermostat is relatively low at 172 degrees with a 180 degree available. The final engine temperature is regulated by the ECM by cycling the radiator fan. During driving (in town and highway) the temperature would increase to about 195 degrees, the fan would turn on lowering the temp to around 185 degrees, the fan would turn off, repeat. Why it is designed this way I have never be able to fathom.

Solution: Since I was never able to pinpoint a specific failure point and didn't want to waste money replacing radom components, I resorted to the old, tried and true, method of blocking about 3/4 of the radiator with cardboard during the winter months. Perhaps changing the coolant temp sensor would have changed the above readings.