Nemisys Advanced ClassNemisys Advanced Class

Fuel Trim

Idle Test Results 2500 RPM Test Results Possible CauseRich Ideal Vacuum LeakIdeal Rich Low Fuel VolumeRich Rich Low Fuel PressureLean Ideal Contaminated Crank CaseLean Lean Leaking Injectors

IAC Counts High• Spec 10 to 30• High IAC counts

– LTFT over +10– MAP normal .8 to 1.5 Idle

• Check ignition• Dirty intake valves,

Injectors, or Throttle plates

• Leaking EGR • Check fuel pressure

and volume

• Spec 10 to 30• IAC Counts High over 40

– LTFT over +10– MAP sensor high or MAF

sensor low <5• Sticking IAC• Dirty intake valves,

Injector, or Throttle plates • Check fuel pressure and

volume• Low Manifold pressure or

compression problems• IAC motor stuck open

Fuel Control Test

Clear Flood Equipped Vehicles

A) DataStream• TPS• Injector Pulse Width

B) KOEO

C) WOT• TPS 4.3 To 4.7 Volts• Injector Pulse Width 0.0

Scan Tool Fuel Control Test(Easy to get HO2S)

• 1) Disconnect HO2S• 2) Datastream

– HO2S– Injector Pulse Width

• 3) Volt Meter At HO2S Signal Return Wire at O2 sensor• 4) KOER, Engine At Operating Temperature, 1000 Rpm• 5) Place One Finger On PCM HO2S Signal Return Wire to the PCM• 6) Place Another Finger At Battery Positive

– Datastream HO2S - 1 Volt– Datastream Injector Pulse Width - Will Drop– Volt Meter HO2S - 0 Volt

• 7) Place Finger At Battery Negative– Datastream HO2S - 0 Volt– Datastream Injector Pulse Width - Will Rise– Volt Meter HO2S - 1 Volt

O2 Sensor Propane Test• Propane enrichment testing to check that the O2

sensors are working properly

• Select, graph and zoom the O2 sensors

• Propane enrichment increases the O2 output above .91 volts, preferred is closer to 1.0 volt.

• Keep adding propane until RPM decreases, to get the maximum output

• Remove the propane to see how fast the voltage decreases. It should decrease in a straight line

Timing Advance Datastream Test

• Datastream review of Timing Advance versus RPM

• The timing advance should follow RPM, except when in Wide Open Throttle, when timing advance decrease slightly

• Datastream review of Timing Advance versus TPS

• TPS moves and Spark changes good reaction and timing curve

Timing Advance Datastream Test

• Datastream review of Timing Advance versus MAP

• The spark advance must follow the MAP sensor load changes

Timing Advance Datastream Test

MAF Test• 1) KOER, Engine At Operating Temperature• 2) Scan Tool Datastream

– MAF GPS• (Frequency May Be Substituted For GPS)

• 3) Mark Points Of MAF GPS On Graph Paper – 1000 Rpm– 1250 Rpm– 1500 Rpm– 1750 Rpm– 2000 Rpm

• 4) Connect Plot Points, Graph Line Should Rise Smooth

Good MAF Graph

1000 1250 1500 1750 2000

GPS

RPM

Bad MAF Graph - Out of Calibration

1000 1250 1500 1750 2000

GPS

RPM

Bad MAF Graph - Air Leak

1000 1250 1500 1750 2000

GPS

RPM

MAF Test• Select and graph RPM and

MAF

• Ford MAF sensor should reach a output of above 3.5 volts with a snap throttle

GM MAF TEST• GM with a snap throttle should go

above the 5.4 kHz for a good sensor output

• Check MAF sensing wires or clean the wires, and check the duct work for leaks after the MAF sensor

GM MAP Sensors

8-9”.9-1.1 V21”

11-12”1.5-1.7 V18”

14-15”2.1-2.3 V15”

17-18”2.5-2.7 V12”

20-21”3.0-3.2 V9”

23-24”3.5-3.7 V6”

26-27”4.0-4.2 V3”

29-30”4.5-4.7 V0”

Scan DataVoltageVacuum

GM/Chrysler BARO Readings

3.8-4.0 V25-26”4000 to 5000’

3.9-4.1 V26-27”3000 to 4000’

4.1-4.3 V27-28”2000 to 3000’

4.3-4.5 V28-291000 to 2000’

4.5-4.8 V29-30”0-1000’

VoltageBaro PressureAltitude

Chrysler MAP

8-9”.9-1.10 V21”

11-12”1.5-1.7 V18”

14-15”2.1-2.3 V15”

17-18”2.5-2.7 V12”

20-21”3.0-3.2 V9”

23-24”3.5-3.7 V6”

26-27”4.0-4.2 V3”

29-30”4.5-4.8 V0”

Scan DataVoltageVacuum

Ford MAP Sensors

96 Hz21”

105 Hz18”

114 Hz15”

123 Hz12”

132 Hz9”

141 Hz6”

150 Hz3”

159 Hz0”

Frequency in HZVacuum

FORD BARO Readings

144-150 Hz25-26”4000-5000’

147-153 Hz26-27”3000-4000’

150-153 Hz27-28”2000-3000’

153-157 Hz28-29”1000-2000’

159-163 Hz29-30”0-1000’

Altitude Vs. Frequency

MAP Sensor Test• 1) Scan Tool Datastream

–Map Sensor Voltage• 2) KOEO• 3) Attach Vacuum Pump To Map Sensor

Vacuum Port• 4) 0 Vacuum, 3.9 To 4.7 Volts• 5) 18 To 20 Inches Vacuum, .8 To 1.5

Volts

Cranking Vacuum/Pressure

• Cranking Vacuum can be tested using the MAP Sensor

• The voltage or pressure should decrease in response to vacuum

Reaction Testing• Testing the TPS against the MAP sensor

shows the response of the sensors

• They should follow each other.

• This test will verify CAM to Crankshaft timing

• This test will verify if the TPS sticks when closing

TPS Quick Specs

.6 to 1.1 volts

Wide Open Throttle 2.6 volts above stored minimum TPS

Chrysler

.8 to 1 volt

Wide Open Throttle 4.3 minimum

Ford

.29 to .58 volts=0% closed cold

.4 to .58 volts closed=0% warm idle running

GM Port Fuel Injection

.55 to .75 volts=0% closed

Cold / Warm GM Throttle Body Injection

TPS Sweep Test

• 1) KOEO

• 2) Scan Tool Datastream

–TPS

• 3) Open And Close TPS, Smooth Linear Rise

Two Wire Sensor Testing• Check for Voltage supply

– Voltage supply must be above 4.6 volts

• Scan tool should read cold –40°F

• Short the pins in the connector together

– Reading on DVOM should be less than .050 mv

• Scan tool reading should be above 260°F

Three Wire Testing• Check for Voltage Reference

– Range 4.9 to 5.1 volts• Check for proper ground

– Red lead at sensor ground and black lead at battery ground, voltage should read under .050mv

• Short VREF pin and Signal pin together– Datastream should read the same as VREF

• Short signal pin and ground pin together– Datastream should read zero

Cylinder Misfire Testing• Engine at operating temperature• Vehicle at cruise speed• Monitor rear or post HO2S

– Base line voltage .430mv to .470mv• Rear HO2S voltage high

– Secondary Ignition miss fire• Rear HO2S voltage low

– Lean Injector miss fire

Catalyst Test 1• 1) Engine at Operating Temperature • 2) All Basic Engine Functions Must Be in Good

Working Order• 3) Raise Engine Rpm to 2000 and Hold Steady• 4) 3 Minutes Minimum• 5) Monitor HO2S Sensors Upstream and Downstream• 6) Upstream Should Be Swinging Rich to Lean• 7) Downstream Should Be Steady With Small Swing of

430 to 470 Mv

Catalyst Efficiency Monitor

Pre-HO2S Post-HO2SUpstream HO2S Downstream HO2S

S1 S2

800 mv

450 mv

200 mv

470 mv

450 mv

430 mv

Catalyst Test 2• To test for a plugged Catalytic Converter, graph MAP Voltage• With the engine running at 2000 RPM for 3 minutes note what

MAP Voltage is, it should be around 1.2 to 1.6 Volts• Snap the throttle to wide open from 2000 RPM• MAP Voltage will rise from 2000 RPM at wide open throttle to

approximately 3.8 to 4.2 Volts• When the engine returns to idle MAP Voltage should return to 1.2

to 1.6 Volts in less than 3 seconds• If it takes longer than 3 seconds the Catalytic Converter maybe

plugged

Charging Systems Test

• 1) KOER• 2) At Idle verify Battery Volts• 3) At 2000 RPM verify Battery Volts

–Turn all accessories on•Voltage should rise to 14 to 15 volts

Cranking Voltage Test• Record the voltage• Put the engine in Clear Flood mode• Crank the engine for 15 seconds• Cranking Voltage should not go under 9.6• Recovery Voltage should come close to the

recorded voltage in less than 7 seconds