90 Expedition. Need advice on what to check to fix problem. I have replaced all 4 of the 02 sensors, cleaned the mass airflow sensor with CRC cleaner, clean air filter, and smoke test for possible vacumn leaks. Previous to all this work a few months back I clean the mass airflow sensor, clear the codes drove about 1,500 miles to California and back to Vegas no problems no codes popped up no check engine light. 3 days after being back in Vegas check engine light comes back on with the same problem.

 

Have you checked the MAF sensor?
Check the MAF Sensor

1. Turn the engine and ignition off. ...
2. Attach the positive probe of an ohmmeter to the terminal on the MAF marked SIG, and the negative probe to the terminal marked GND.
3. Take a reading from the ohmmeter -- damage to the hot wire element will be indicated by an open circuit.

 

thanks, i will check that out.

 

thank you,