I have A 94 EXPLORER 4.0 V6 NEW ENGINE SO THE DIG. PORT DOESN'T WORK....I DID A TUNE UP AND IT RAN GOOD FOR A DAY AND NOW THE " CHECK ENGINE" LIGHT COMES ON AFTER A FEW MINUTES DRIVING (LONGER IN THE AM) AND IT RUNS A BIT ROUGH. i CAN'T FIND NO VACUM LEAK AND NOW i AM STUCK...CAN ANYONE HELP ME OUT?