Q: Bad fuel mileage, no black smoke, no check engine light.

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My car has an issue where I'm getting under 20 mpg, I have inspected the fpr, Maf, and the fuel injectors. Car also has sluggish acceleration, and the engine shudders under WOT below 3000 rpm. My car has 273,000 miles

My car has 273000 miles.
My car has a manual transmission.

Hi there. Most of the time, poor fuel mileage is due to dirty O2 sensors, EGR valve, mass air flow sensor or throttle body itself. If these components are dirty or damaged, it can also cause engine misfiring or rattling during acceleration as you’ve described. To identify the source issue, it might be a good idea to have a professional mechanic come to your location and complete a car is getting worse gas mileage inspection.

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