Q: Car makes a rattling noise then accelerating though 3rd/4th when cold
My 2012 Ford Flex makes a rattling noise when the engine is cold and accelerating through 3rd and 4th gear. It only does it once then doesn’t do again til the engine is cold again. If I start the car and let it warm up for a few mins it doesn’t make the noise when accelerating.
This can be caused by engine running too lean when cold and causing the rattle under load. Try to have the mass air sensor cleaned to see if problem stops? If not then have mass air sensor replaced and the fuel injectors cleaned. This should fix the issue.
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