Pontiac Repair: 2000 firebird v6 3.8, mass air flow sensor, mass air flow

Question
Sometimes my car will start fine other times it just keeps turning over.Then as im driving it will stall out, when it does this it usually makes a backfire then dies.When attempting to restart it it will sometimes be in a low idle but when i give it gas it does not respond.Then after sitting for awhile it will start right up.My service engine soon light is on.The codes are reading 1514 and 421, ive already changed my MAF twice can you help?

Answer
Hi Mike:

The 1514 sensor is a corolation dtc. meaning the engine computer looks at the throttle plate angle and compairs it to the engine rpm mass air flow reading and sees if they match. If not it will store the code. Did you replace the mass air flow sensor with a GM sensor or an after market part? If the problem was there before the sensor was replaced then the sensor was not the cause. If it cropped up after the sensor was replaced then the sensor may have cause the problem. My gut feeling here is that there is possably an issue in the throttle body assembly or and issue between the throttle body and the engine computer with a bad connection or high resitance is the wiring between the 2. Does this car have a lot of miles on it? Also with out the air of a scan tool this is going to be a VERY hard problem to find. Just going on the basis of the code setting doesn't give you much to go on. if you had a scan tool you could see what the conditions where when the code set. As for the 421 code? I don't know what that is a 420 is a catalitic converter code buy I don't think the v6 has a 421 .