2007 ford f150 with v6 engine. 110K miles. tuned up at 98k. brakes checked - nothing hung up. front end aligned. suddenly started gobbling up fuel. any ideas? bad oxygen sensor maybe? thanks for any input.
A bad O2 sensor would cause the Check Engine light to come on.
The two things I check for when an engine suddenly starts using fuel are, a thermostat that’s stuck open, and a faulty coolant temp sensor for the computer.
If the thermostat is stuck open, the coolant doesn’t get up to operating temperature. So the computer doesn’t switch to the closed loop mode and it adds more fuel.
Same thing if the coolant temp sensor for the computer is faulty.
If the sensor is telling the computer that the coolant never gets to operating temperature when it actually does, the computer thinks the engine is cold, and it adds more fuel.
Tester
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thank you. I appreciate the quick response and your time.
thank you. I appreciate the quick response and your time.
First things first: What method are you using to determine that it’s using more fuel than it used to?
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On a 2007 my first guess is the coolant thermostat has sprung a leak. That gadget sits in coolant all the time and eventually corrodes. It’s been in there 10 years. That should show up in the dash temp gauge showing your engine is running cooler than normal, but if you haven’t been monitoring where the needle normally sits, you might not notice. It doesn’t take very much reduction in coolant operating temperature to reduce mpg’s noticeably.