Low coolant temp. poor performance

[white94]

I have read threads about people's O2 sensors and how they affect performance. My mileage is dropping and on trips the check engine light comes on. Performance is poor climbing hills, etc.

The only difference is that, although the engine is warm, the temp. gauge rarely gets past the left side of normal. I changed the thermostat, but was wondering if my coolant temperature sensor could be the problem - would it send an incorrect message to the fuel system? My next qualm is that i believe the coolant temp. sensor and the temperature sending unit to the dash are unrelated. Is that correct? This is Phoenix and I know it isn't running cool!!

 

[SWIGNER]

COOLANT SENSOR

I recently changed my coolant sensor after retrieving a P0125 code (insufficient coolant temperature for closed loop fuel control). Before I just swapped my original out for a new one, I made sure to check out it's resistance using a multimeter at various temperatures. The resistance was off quite a bit. If I placed the sensor in boiling water (212 degrees fahrenheit), it would give me a resistance as if it were in about 140 degrees fahrenheit. Obviously, I swapped it out for a new one thinking that this would relieve me of my check engine light frustration. About four days later, it came back on. Guess what? I retrieved the same code again. Now I'm looking at my coolant temperature sending unit and thermostat to see if this might be the problem. I am experiencing the same problems as you, however, with the temperature gauge never even getting close to the normal range. I am curious to see what you find out about your X.

 

[MrShorty]

retrieve the trouble code from the computer. this will tell you what problem the computer is seeing. that will give you a good start to your troubleshooting.
about the temperature sensor, my '92 uses two: one for the computer, and one for the dash guage.

 

[Bottomlesspit]

White94,
You are correct in that the ECT and the guage temp sensors are different and seperate items. The ECT sensor sends the coolant temp to the computer which uses the info to alter the injector pulse times for fuel to the engine. The temp sensor is only used to send info directly to the dash guage.
If the ECT is out of tolerance then it sends bad info to the computer which will either lean out or richen up the fuel mixture. If the ECT says it is cold the fuel injectors will pulse longer, sending more fuel to the engine to burn...thus running rich. A cold engine needs a richer mixture to operate. Of course this is bad for the engine...if it is actually running at normal temp... because the extra fuel is playing games with the O2 sensors that are trying to balance the A/F ratio out, the extra fuel is washing down the cylinder walls, and gas mileage is going down.
The ECT will have no effect on your guage reading...which is usually not that accurate anyway. Either your guage or sending unit is bad, or your cooling system (thermostat, radiator cap, coolant mix, etc) is not operating properly.
I just changed out a faulty thermostat in my X and it brought the temps up from full cold to right in the middle of the guage. My heater works again!!! The new thermostat had NO good effect until I installed the radiator cap...then the temp went up. With the cap off (trying to burp the system) the temps stayed on cold indefinitely.
What temp thermostat did you install? Are you sure it is in properly?
We'll give this some more thought. Keep us up on what you are finding out.
Ken

 

[scratched 95]

Swigner, where did you find the resistance readings for the sending unit? Care to publish them?

Thanks,

Ed

 

[RTStork]

You could also hook up an auxillary temp gauge. I have seen Ford guages go bad before. This would rule out a bad gauge.

 

[natedogco2007]

i am having this problem too. i have replaced both temp senders as well as the gauge and it doesn't move and the check engine light keeps coming on. can anyone help? this is soo frustrating. i hate this. the scanner tells you what is wrong and then you replace it and it still don't work.

 

[TPLYNCH]

Is it safe to assume you replaced the thermostat itself?

 

[Bigred08046]

p0125 low temp

where is the ECT anyway? Is it under the throtle body screwed into manifold? Has anyone resolved this code/problem??

 

[Jason_25]

Re: p0125 low temp

Originally posted by Bigred08046
where is the ECT anyway? Is it under the throtle body screwed into manifold? Has anyone resolved this code/problem??

Yep the one with one wire going to it is the dash sender. the one with 2 (3?) wires coming out of it is the ECT. They are right beside each other.

 

[Bigred08046]

P0125

Ok it's fixed!! Replaced sensor, ($15)Tstat, ($7)new Anti Freeze ($6)and radiator cap.($7) One word of caution...make SURE that the air valve on the t-stat is at 12:00...on the top. Normal temp on gauge and runs much smoother. I didn't test sensor but I think the real "bad" part was the radiator cap. Thank you for this board.

 

[Bigred08046]

P0125

Ok it's fixed!! Replaced sensor, ($15)Tstat, ($7)new Anti Freeze ($6)and radiator cap.($7) One word of caution...make SURE that the air valve on the t-stat is at 12:00...on the top. Normal temp on gauge and runs much smoother. I didn't test sensor but I think the real "bad" part was the radiator cap. Thank you for this board. PRICELESS!