Car will now idle correctly

PEGGY ADAMS

MEMBER
2011 FORD FIESTA
1.8L
4 CYL
FWD
MANUAL
109,000 MILES

If you come to a stop light the car will not idle correctly. It either revs up to 3000 rpms or the idle dips below 1000 rpms and will stall. The car immediately starts right back up. At times driving down the road you get a slight lack of response from the gas pedal with lunging from the car. We have replaced the following. Air filters, map sensor. It was placed on a diagnostic computer with the following codes
P0300 random misfire detected
P0068 manifold absolute pressure / mass air flow - throttle position correlation for vehicles with idle air control valve
P0101 mass or volume air flow a circuit range/performance
P0101 mass or volume air flow a circuit range/performance
P0420 catalyst system efficiency below threshold (bank 1)
I doubt know where to begin.I'm on a limited income and can not afford a large service bill. Please provide some suggestions.

1 Reply

WRENCHTECH

MECHANIC
20,761 POSTS

It appears you may have a bad Catalytic Converter but that is unrelated to the other issues. The main issue has to do with the mass air flow system. The very first thing to do is check the car very carefully for any vacuum leaks or leaks in the intake snorkel. These will have a major effect on the Mass Air flow. The intake tube must be air tight between the Mass air flow sensor and the throttle body.

If all that checks out, you may have a bad Mass Air flow sensor.