1997 Ford Ranger MASS AIR FLOW SENSOR

What do you mean by humming? Does it sound like a honk or buzzing sound? Has the check engine light come on? If it is more like a honking sound especially when coming to down to idle it is usually the idle air control valve that makes this sound. If it is different then get a scanner and monitor your fuel trims. If they long term is around +20% then check your pcv hose for a leak. They usually collapse and the air been sucked in is making that humming noise. Also monitor your mass air flow sensor at idle. Your grams per second should be around 4 grams per second.

I should have used the word buzzing its not a honking noise. It only happens at idle in gear and in park. I have also replaced the idle air control valve in the past year.The pcv and hose have also been replaced in the last year. The check engine light is not on and I have used my scan tool and dont get any error codes. I have had this truck for just over 2 year and have replaced almost everything related to emissions system.

Thanks Todd

Sorry I am getting back late. I had an issue once where the camshaft position sensor synchronizer was making that same noise you are describing. Get a stethoscope or a long screwdriver and listen to see if the sound is coming from the Camshaft Position (CMP) sensor synchronizer. If it is replace the synchronizer assembly. Good luck and keep us posted please.

The problem was the idle control valve. What I’m not sure of is why it failed. I replaced it less than a year ago. Was the one I purchased defective or did something else make it fail?