WHEN STARTS EPC LIGHT ON MOTOR BACKFIRE, HESITATE, IF START 3RD TIME RUNS FINE IN CLOSED LOOP, CHK VACCUM LEAK NOT FIND, CHANGE MAF WITH USED ONE SAME PROBLEM, CHK ALL FOUR ABS SENSER, CLEAN IT PUT BACK ,SAME PROBLEM, NO CHK ENGINE LIGHT ON,NO CODES. IAM ALSO TECH. NEED HELP