Figure 26.1 Valve deposits on the intake valves can cause hesitation during acceleration, especially if the engine is cold.

Figure 26.2 Typical throttle-position (TP) sensor.

Figure 26.3 Many areas of the country use gasoline that is blended with up to 10% ethanol (ethyl alcohol). Sometimes too much alcohol can cause driveability problems.

Figure 26. 4 This throttle body needs to be cleaned Figure 26.4 This throttle body needs to be cleaned. The deposits on the back (engine) side of the throttle plate can cause rough idle or stalling due to lack of proper air flow into the engine.

Figure 26. 5 This engine does not have any vacuum while cranking Figure 26.5 This engine does not have any vacuum while cranking. This newly overhauled engine had been assembled and the valve had not been properly adjusted. Cranking vacuum should be greater than 2.5 in. Hg.

Figure 26.6a This is a voltmeter reading of the battery voltage on a vehicle that has a defective starter. The 7.84 volts reading on the meter is much lower than the specification of greater than 9.6 volts.

Figure 26. 6b This meter indicates a cranking voltage of 10 Figure 26.6b This meter indicates a cranking voltage of 10.32 volts, which is within specifications.

Figure 26.7 This stuck-open thermostat caused the engine to fail to reach normal operating temperature. As a result, the fuel economy was much lower than normal and it failed a state vehicle exhaust emission test due to excessive hydrocarbons (HC).

Figure 26.8 This distributor cap came off an engine that seemed to run okay. The only problem was that the vehicle failed an exhaust emission test for excessive hydrocarbon (HC) emissions.

Figure 26.9 This badly eroded water (coolant) pump caused the engine to overheat.