Having a 10 year business truck with moderate miles driven 'gingerly' daily, there are things that can come up. I appreciated Allen's extra effort in diagnosing the problem. He offered suggestions as to the fault, but went the extra mile and after a closer look found a faulty injector (instead of a valve or cylinder problem). Even with computer diagnostics, readings can only identify an area of a problem, not the specific cause of the problem. His teams' further investigation was greatly appreciated and cost much less than an engine overhaul. I feel the extra effort saved me money and deserves an excellent rating.