The car hesitates badly, in the worst case the car will have a hard time getting over 10 or 15 MPH. The car failed the emissions test because of Nox.

When you disconnect the cable to the air mass meter, the car runs fine. When the sensor is connected we don't get the 1-2-1 code for the air mass meter. We've taken the sensor out and don't see any broken wires or obvious problems. Since we don't see the air mass meter code, we hesitate to buy one more expensive part that may not fix the problem. Any suggestions?

When the air mass meter is connected and the car is running very roughly, restricting the air intake by partly blocking of the flow between the air cleaner and the mass air sensor make the engine run much better.

We have replaced the coolent temp sensor, one ignition coil, the EGR temp sensor, and the big rubber air horn that goes between the mass air sensor and the throttle body.