Fluctuating Temp Gauge Issue...
Apologies if this is covered in an existing thread. I found this issue in a few threads, but I've tried the solutions listed with no luck... The symptom is a fluctuating reading on the temp gauge of my 1999 Ranger 4.0 liter. It gets to the middle (normal) and then dips down almost to the cold and works its way back to the middle over and over again. This cycle runs about every 2 minutes or so and I recently had a couple codes come up (PO171 and PO174) which indicate lean conditions. Truck seems to run just fine but not sure how to fix the gauge. I’ve replaced the thermostat (180 degree) and also replaced both the Temp Sensor and Temp Sending unit in the hopes that it would resolve the problem. I cleared the codes and so far they haven't recurred but the gauge is still oscillating… The coolant is clean (changed this year) and as far as I can tell there is no air pocket in the coolant. I have NOT checked the gauge but wonder if a failed gauge would fail in this way. Once the truck warms up I have heat from the heater, etc and it doesn't seem to lose any heat that I can feel. I'm the original owner and prior to this, the truck would only fluctuate once when the thermostat opened and the "cool" coolant from the radiator hit the sensor after which the temp would stabilize at the half-way mark. That being said, has anyone had this problem and what was the fix? Thanks for any info/help!
1999 Ford Ranger XLT 4x4 Supercab. Offroad Option with 5-speed, 4.0 liter V-6 and 4:10 axles.