It starts fine and for the most part runs fine. But I can be driving down the hwy and it will shudder and sometimes just die as I'm driving. And the tach will jump all over the place. Sometimes it just comes back on, other times I have to pull over and start it. The ignition system has recently been replaced. The fuel pump and filters have been replaced. A coworker mentioned something about the intake manifold might have a leak. I'm at my wits end and could use some guidance. You know, other that a 50 cal. Through the block. All the work I mention has been done by a certified mechanic and he is at a loss for what's going on. Thank you for your time.
My car has 158000 miles.
My car has an automatic transmission.
This may be a sign of a dirty or failing mass air flow sensor. The mass air flow sensor reads the air intake as it is mixed with fuel prior to being injected into the motor. When this fails, this can cause an imbalanced air/fuel load to be supplied to the motor which results in an over fueling or under fueling situation depending on the conditions. This is will often times cause a jerking reaction as the motor starves for fuel or is overloaded with fuel resulting in a momentary flooding condition.
This may also be related to a faulty throttle position sensor. The throttle position sensor reads the position of the throttle plate inside the throttle body in relation to your foot position on the gas pedal. Based upon the inputs from the sensor reading your foot's position on the pedal, the ECU then makes the direction to supply more or less fuel to the motor. When this sensor is not working properly, this can cause intermittent responses when pressing the gas pedal as you describe. I would suggest having a professional from YourMechanic come to you home to diagnose the shuddering concern and replace any parts that need repair.
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