ENGINE TUNE UP ACTUAL SCRIPT 2026
COMPLETE SOLUTION MARKED
◉ Maybe a bad 02 sensor or intake air temperature sensor. Both of
these relay signals to the PCM/ECM that directly affects control of
the fuel. Answer: Car with electronic fuel injection gets piss poor gas
milage. Measured value blocks show the engine is running rich.
What could be the cause?
◉ Fuel mixture is likely too rich. Too high voltage indicates a rich
mixture.. Answer: With a DMM connected, an O2 sensor reads above
550 millivolts, constantly. What's going on?
◉ 2 Types of MAP sensors. Answer: 1. Analog Signal type-tested
with a voltmeter
2. Frequency signal type-tested with a hertz meter or digital
tachometer
◉ Frequency type MAP sensor. Answer: This type of MAP sensor
measures pulses per second (Hz) and converts them to revolutions
per minute. Therefore, it will have a constant signal voltage.
◉ Closed Loop Operation. Answer: If the coolant temperature sensor
tells the PCM/ECM that the engine has not yet warmed up, even
,though it has, the system will not go into ______ ____ _________ and will
run rich
◉ TBI fuel injector stuck open. Answer: Crank-no-start, fuel is
POURING from the TBI injector when the engine is cranked and even
when the cranking is stopped until pressure runs out.
◉ PCM driver for the TBI injector is shorted out. Answer: crank-no-
start, fuel is POURING from the TBI injector when the engine is
cranked. Disconnect the connector to verify. The injector should hold
the fuel back on its own.
◉ Causes of turbocharged vehicle performing poorly and lacking
power:. Answer: 1. Restricted intake duct
2. Wastegate stuck open
3. failed turbocharger shaft bearings
◉ Distinctive O2 sensor normal closed loop, adaptive fuel
management pattern.. Answer: O2 sensor voltage on a scope
analyzer. Pattern observed, changes from 0.25 volts to 0.8 volts in a
regular series of flat-topped hills.
◉ Ammeter. Answer: tool used to troubleshoot a slow drain in an
electrical circuit
, ◉ Proper procedure for checking starting circuit. Answer: 1. Check
crank speed
2. Check starter current draw
3. Check battery voltage while cranking
4. Check voltage drop of the starter motor circuit
◉ ~150 amps. Answer: = typical starter current draw for 4 cylinder
engines
◉ ~200 amps. Answer: = typical starter current draw for 6 cylinder
engines
◉ ~250 amps. Answer: = typical starter current draw for 8 cylinder
engines
◉ >9.6 volts. Answer: Battery voltage should remain above this level
during the starter current draw test and the engine should spin
rapidly.
◉ Starter current draw (amperage) higher than normal. Answer: -
May be short circuit in starter motor
-May be mechanical issue causing binding in the engine
COMPLETE SOLUTION MARKED
◉ Maybe a bad 02 sensor or intake air temperature sensor. Both of
these relay signals to the PCM/ECM that directly affects control of
the fuel. Answer: Car with electronic fuel injection gets piss poor gas
milage. Measured value blocks show the engine is running rich.
What could be the cause?
◉ Fuel mixture is likely too rich. Too high voltage indicates a rich
mixture.. Answer: With a DMM connected, an O2 sensor reads above
550 millivolts, constantly. What's going on?
◉ 2 Types of MAP sensors. Answer: 1. Analog Signal type-tested
with a voltmeter
2. Frequency signal type-tested with a hertz meter or digital
tachometer
◉ Frequency type MAP sensor. Answer: This type of MAP sensor
measures pulses per second (Hz) and converts them to revolutions
per minute. Therefore, it will have a constant signal voltage.
◉ Closed Loop Operation. Answer: If the coolant temperature sensor
tells the PCM/ECM that the engine has not yet warmed up, even
,though it has, the system will not go into ______ ____ _________ and will
run rich
◉ TBI fuel injector stuck open. Answer: Crank-no-start, fuel is
POURING from the TBI injector when the engine is cranked and even
when the cranking is stopped until pressure runs out.
◉ PCM driver for the TBI injector is shorted out. Answer: crank-no-
start, fuel is POURING from the TBI injector when the engine is
cranked. Disconnect the connector to verify. The injector should hold
the fuel back on its own.
◉ Causes of turbocharged vehicle performing poorly and lacking
power:. Answer: 1. Restricted intake duct
2. Wastegate stuck open
3. failed turbocharger shaft bearings
◉ Distinctive O2 sensor normal closed loop, adaptive fuel
management pattern.. Answer: O2 sensor voltage on a scope
analyzer. Pattern observed, changes from 0.25 volts to 0.8 volts in a
regular series of flat-topped hills.
◉ Ammeter. Answer: tool used to troubleshoot a slow drain in an
electrical circuit
, ◉ Proper procedure for checking starting circuit. Answer: 1. Check
crank speed
2. Check starter current draw
3. Check battery voltage while cranking
4. Check voltage drop of the starter motor circuit
◉ ~150 amps. Answer: = typical starter current draw for 4 cylinder
engines
◉ ~200 amps. Answer: = typical starter current draw for 6 cylinder
engines
◉ ~250 amps. Answer: = typical starter current draw for 8 cylinder
engines
◉ >9.6 volts. Answer: Battery voltage should remain above this level
during the starter current draw test and the engine should spin
rapidly.
◉ Starter current draw (amperage) higher than normal. Answer: -
May be short circuit in starter motor
-May be mechanical issue causing binding in the engine
