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Low power and engine response complaints can be caused by very different reasons and require different repairs, but are often the same complaint from the operator. A discussion with the operator is needed to help correctly diagnose whether to repair for low power or slow response. At times, full engine horsepower is available, but the operator still complains of low power. Repairs for low power would not provide a satisfactory result, and may consume many hours with expensive repairs. The actual complaint may be the engines ability to respond to a changing load or shifting gears.Normally, engine power can be measured to determine if it is within specifications. When troubleshooting a "low horsepower" complaint, if fuel consumption, timing, speeds, and manifold pressure are within specification, do not spend additional time looking for "low engine horsepower." If it is still believed that performance of the vehicle is below that expected, look for horsepower losses in the transmission, differential, clutches, parasitic loads (fan, air compressor, air conditioner, etc.), tires, low fuel density or high temperatures, but not the engine.Owner/Operator Input
The following are some of the questions which should be asked before beginning any diagnosis or repair for an engine performance complaint. THERE ARE NO HARD AND FAST ANSWERS FOR THESE QUESTIONS. There are many different truck engine specifications and truck vehicle specifications which will provide acceptable results. There are also a variety of customer expectations which are acceptable. The answers to these questions will give you a better understanding and perspective on the complaint and may identify characteristics which will help pinpoint the cause of the complaint quickly.1. Is there a particular operating condition when the complaint occurs? Low power and response complaints require different repairs. Complaints during shifting will be different from complaints of low power in certain speed ranges or in certain terrains.2. What are the customer's expectations for fuel mileage and power and why does he have those expectations? Comparisons to other trucks on the road often have many unseen variables. If comparison to others is the basis for the complaint, you must insure that the comparison is valid.3. What are the normal upshift and downshift rpm's? If the shift points are too high, find out why. If the driver is operating this way out of habit or because he is taught to drive that way, arrange for him to receive the Caterpillar driver training information. If his shift points are too high because of poor performance, you may be able to correct this in the engine.4. What are the normal routes and loads for the truck? You should be looking for the amount of city versus highway driving, versus mountainous, heavy versus light loads, and cold climate versus warm climate.5. Can the operator detect a misfire? This can lead you to a diagnosis of just one cylinder rather than an entire engine system.6. Does the engine smoke excessively, and if so, under what conditions? Excessive smoke can give indications about engine settings and engine internal conditions.7.