High Idle and Fluctuating temp guage

[mrossirr]

Just started doing this. On cold starts everything seems normal. Idle around 6- 800 rpms. Temp guage about a quarter of the way up from C. Drive about a mile and rpms at about 1500 and temp guage above the halfway mark. Could it be thermostat or sensor ?

Thanks in advance.

 

[drbenz]

Are you saying that your temp guage starts cold 1/4 way up the guage? With the engine speed change something is not right but it could be just the idle control. Which engine do you have?

 

[mrossirr]

just sitting warming up is when the guage goes to a quarter way up . When i start to drive is when it goes crazy. 4.0 sohc engine.

 

[2000StreetRod]

temp gauge

The temperature gauge and the sensor associated with it have no effect on the operation of the engine. The PCM has a dedicated sensor to read the temperature of the engine coolant. You could have a defective thermostat, temperature gauge or associated sensor, or erratic electrical system among other problems.

As the engine warms up the commanded idle speed should decrease. If the engine is actually running at 1500 rpm when the throttle is closed then the engine will rapidly overheat when the vehicle is in gear and stopped. Make sure that the throttle body plate is not sticking open. Test the TPS. Clean the IAC valve.

Check the coolant level. If it drops below the engine coolant temperature (ECT) sensor the PCM may think the engine is still cold when it has warmed up and command a high idle speed. Don't let your engine overheat while attempting to locate the source of the problem.