The intention of this test group was to evaluate the effectiveness of the Portland inspection maintenance (I/M) program on light duty trucks (LDT's). 105 LDT's were recruited from the Portland area and tested in their as-received condition. The testing on each LDT consisted of a DEQ Idle Test, HTS Idle Test, FTP, Highway Fuel Economy Test (HFET), 50 MPH Cruise Test, Two Mode Test, two Four Mode Tests (one with a spark plug disconnected), Propane Gain Checks and a complete diagnostic check. All LDT's which failed the DEQ inspection test were taken to local repair facilities upon completion of the initial test sequence. The mechanics were told to make the necessary repairs to pass the DEQ inspection test with no mention being given that the vehicle was involved in a test program.