1999 Ford Ranger 4 cyl Two Wheel Drive Manual 110000 miles
Only during temperatures below 40 degrees, the engine takes 30+ minutes to get warm. When previously it would get heat in a short five minutes, and be at running temp in 15 min. The engine will only warm up if the heater is shut off. If the heater on, or defrost on the engine will never warm up, but it will admit very mild heat. If the heater is off and the engine gets to running temperature, as soon as the heater is turned on the engine temp will drop within a minute to a cold start up temperature, and the heat will disappear to a mild temperature again too.
Hwy or city driving has no effect on how fast the engine heats up. Also the engine may have a high idle after start up from time to time, but will go away. Or an occasional shimmy felt from the engine while idling at a stop.
I have replaced the thermostat, fan clutch, 2 radiator caps, and dash gauge temp sensor, completed a full flush, flushed out the heater core by its self for any blockages, and did several pressure tests (no leaks). Also the blendoor works perfectly.
Before the cooler temperatures outside, I replaced the spark plugs, wires, fuel filter, air filter, EGR pipe, EGR valve, DPFE sensor.
The only engine code I still have is the dreaded P0401 for the DPFE sensor, which I can’t seem to get to stay off no matter how many sensors that I throw at it.
Any thoughts, answers, or solutions to my heat and engine running temp problem is greatly needed, and appreciated… I’m at a complete loss and extremely frustrated.