Temp Gauge Problem

[TJ_Jeep]

Well this is starting to become a headache. Recently my temp gauge will drop all the way down, like its not registering, and the engine idles way high and you cant give it any acceleration or it dies out. But out of nowhere, it will pop back up to the normal temp and run fine, I don't even know where to start with this problem.

 

[SteelHeadz]

It could be a faulty connection to the temp. sending unit or the sending unit itself is faulty.

 

[TJ_Jeep]

But would that make it run bad?

 

[SteelHeadz]

Absolutely. The sensor uses a 5v reference along with the other engine sensors and if the temp sensor has an open short or short to ground, the PCM will compensate for the signal and make it run rough or even stall. The sensor provides an input voltage to the Powertrain Control Module (PCM) relating coolant temperature. The PCM uses this input along with inputs from other sensors to determine injector pulse width and ignition timing. As coolant temperature varies, the coolant temperature sensor's resistance changes. The change in resistance results in a different input voltage to the PCM.
When the engine is cold, the PCM will operate in Open Loop cycle. It will demand slightly richer air-fuel mixtures and higher idle speeds. This is done until normal operating temperatures are reached.

 

[TJ_Jeep]

Well I put a new sensor on, it runs a 100% better. Thanks