2011 AUTOCAR XPEDITOR Vehicle Speed Control Problems

I AM EMPLOYED BY THE CITY OF LOS ANGELES IN THE DEPARTMENT OF WATER AND POWER AS A JOURNEYMAN EQUIPMENT MECHANIC. ASE CERRTIFIED, GM SENIOR MASTER TECH AND FORD SENIOR MASTER TECH. THE DEPTARTMENT RECENTLY PURCHASED A LARGE NUMBER OF AUTOCAR MEDIUM DUTY TRUCKS POWERED BY CUMMINS ISL-G ENGINES. THE ENGINES ARE COMPRESSED NATURAL GAS(CNG) FUELED, SPARK IGNITION, ENGINES AND FLY BY WIRE THROTTLE CONTROL. THROTTLE RESPONSE DOES NOT MIRROR THROTTLE INPUT FROM THE OPERATOR. UPON INITIAL THROTTLE APPLICATION THERE IS A DELAYED RESPONSE OF APPROXIMATELY 1.25 SECONDS AND THE THROTTLE CONTINUES TO BE "LAZY." WHEN THE THROTTLE IS DEPRESSED COMPLETELY TO WIDE OPEN THE ENGINE RUNS UP TO GOVERNED SPEED BUT WHEN THE THROTTLE IS RELEASED THE ENGINE CONTINUES TO OPERATE AT WIDE OPEN THROTTLE FOR APPROX. 1-2 SECONDS. WE EMPLOY PROFESSIONAL DRIVERS THAT CONSIDER THIS DRIVING CHARACTERISTIC UNNERVING. FURTHERMORE NO MECHANIC ON STAFF FEELS THESE CAN BE SAFELY...