does anyone know how to check the ect. when i start my truck up in the morning, it doesnt stay at a high idle very long. i checked the ect with an ohm meter and at cold i got 62k ohms and warm i got 15k ohms. is this ok readings or are they off. what else could be causing this warm up problem. thanks in advance...

 

Those readings don't sound too far off but I can't remamber the exact parameters for the ECT. ECT should be the high idle trigger though. IAC responds to the PCM to control the idle. If the coolant sensor isn't the trouble, the IAC may need cleaning.

 

94, your resistance readings sound like they are in range for a generic thermistor but as a truthful way to check for a good ect you need to look at voltage drop. The ford manual i do not believe provides a resistance specification for the ect. The only specification provided is voltage comming out of the sensor should be between .3 and 3.7 volts. Needless to say the lowest voltage would be present when hot and the sensor generating the highest resistance.

To be honest, even if you check the output voltage with a meeter i am unsure as to what you could compare it to. The proper way would be to use a scanner and read what temperature the pcm has determined the engine is opperating at corrosponding to ect voltage. Before you even go that route, do you have any dtc's? Perhaps one for the ect circuit? You problem could also be caused by a goofy air intake temp if your vehicle is equipped. A faulty iac/isc could also be the culprit but again the only way to verify would be to observe actual engine temp first via the scanner and watch to see how the iac/isc is being commanded.

Sorry i couldnt be of more help. Hope it is at least points you in the right direction. Good luck.

 

94F150Shorty, I had the same problem with my 90 Bronco with 5.0 and AOD transmission. I used a code reader and received code #51 ECT sensor voltage too high so the computer thinks the engine is already warmed up. I changed it for nothing as it was not bad. But it's only $13 so it didn't break me. What I had was a wiring problem. I was told to check for a ground at the wire to the ECT. I unplugged the computer at the left rear of the engine compartment. I checked the ECT plug with a voltmeter with the positive hooked to the battery and it gave me a ground. I started tracing the plug from the ECT back under the plenum, around the back of the engine, near the coil, over to the computer, and the ground went away. SOMEWHERE in that mess there is a short that I apparently moved. The ground went away but I did not find why. I plugged the computer back in, hooked up the ECT sensor and started the engine. The engine regained it's high idle and the check engine light went out. The code reader now says code #11, system OK. I might add that when I checked it with just a test light it wasn't enough of a ground to light the light. I had to use a voltmeter at the low 10 volt setting to find it.