Engine Tune Up Already Verified Answers
Engine Troubleshooting
What could be causing an engine to run with low power? A slow crank, faulty spark plugs, or incorrect
fuel pressure.
What is the purpose of a catalytic converter? To oxidize HC into CO2 and H2O.
What vehicles are designed to o...
What could be causing an engine to run with low power? A slow crank, faulty spark plugs, or incorrect
fuel pressure.
What is the purpose of a catalytic converter? To oxidize HC into CO2 and H2O.
What vehicles are designed to operate in a closed-loop mode under certain conditions? All of the above:
cruise control, idle, and emissions testing.
What does a vacuum hose connected to "P" vacuum indicate? The hose should be connected above the
throttle plate.
What is the most likely cause of a voltage spike not being high enough on one cylinder? A failed spark
plug.
When performing a cylinder leakage test, what does air escaping through the throttle body indicate? A
leak at the intake valve.
What can cause higher-than-normal oxides of nitrogen (NOx) emissions? All of the above: rich mixtures,
excessive EGR flow, and high combustion temperatures.
What would a reading of 8 volts on meter 2 while cranking indicate? An excessive ground circuit voltage
drop.
Why are emission control systems installed on engines? To reduce three specific exhaust products:
hydrocarbons, carbon monoxide, and oxides of nitrogen.
, What should you do next if you've verified a slow crank complaint? Determine the condition of the
battery.
What is the primary function of the EGR system? To recirculate exhaust gases back into the intake
manifold.
What type of voltage increase would you expect when monitoring the TPS signal voltage digitally? A
smooth increase to about 4.5V.
What type of fuel injection system sprays fuel directly into the throat of the intake manifold? A throttle
body injection system.
What is the function of the EGR valve? To recalculate exhaust gases into the intake manifold.
What could cause a car to have low power? All of the above: slow crank, faulty spark plugs, incorrect
fuel pressure, and excessive EGR flow.
What would a reading of 1V on meter number 1 while cranking indicate? An unacceptable voltage drop.
During closed-loop operation, what would you expect to see on an O2 sensor reading? A sluggish sensor
reading around 450-500 mV, indicating it's probably bad.
Why won't a car start with a defective or misaligned crank sensor? The crank sensor can't accurately
detect engine rotation and position.
How is fuel pressure controlled in an electronic fuel injection system (EFI)? Engine vacuum.
What could cause an OBD-II vehicle with a check engine light flashing to indicate poor performance and
low power? A misfire condition detected by the onboard computer.
What would a weak ignition coil likely cause? Engine misfires and poor engine performance.
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