SENSOR REVIEW - Sputter and Hesitation Troubleshooting Guide for the 3000GT (I hope)

SENSOR REVIEW
Sputter and Hesitation Troubleshooting Guide for the 3000GT (I hope)
by ProwlerGT

My opinion:
I'm now convinced that the problem is an old sensor and that the IAC was a separate yet very similar problem. The IAC will deteriorate acceleration capabilities while driving and cause the sputtering while actually on the road and also while at IDLE and/or stopped while in Drive and/or with the A/C on or not.
In any case the IAC will start to need service I'd say somewhere at 70 or 80K if not just needing to be replaced altogether. Still though, my theory here is a compounding one. I have heard reports of the IAC melting the caps (capacitors) on the ECU (or ECM ?; DA MAIN SHIZ DIGGIE MOTHER COMPUTER OF THE CAR) which would cause further electronic instability. I'm wondering if the IAC currents that were likely sent when it was faulty also threw off some other sensor voltages throughout the fuel/engine system and/or if my caps are melted. I just haven't wanted to remove the ECU. I don't like fooling with the motherboard of my car when its been doing just fine sitting under there. Still, since I know I had a bad IAC I should break down and LOOK.
In any case I have decided to review ALL SENSORS in the car, but I do not have a datalogger so this makes things interesting. Will I get one or try to troubleshoot with old fashioned methods? Reading the troubleshooting portions of the manual for the sensors is really helpful I have found ! LOL - GO FIGURE.
Below are the sensors involved in fuel injection which could possibly cause the interruption of it (fuel injection and injector timing). All of the following is from the manual, but I figured it would help me and others to have a REVIEW of sensors all in one place here.

Although I have yet to test these out(no datalogger doesn't help) or replace any of them, from the information I read from the manual which I've grouped here in this review I have deduced the following priority ordered list of which sensors I think may be the cause of these sputter, hesitation, near stalling at stops, etc.. problems.
Again I list these in order of "what I think is more likely causing the problem" down to "the more unlikely sensors causing the problem":

Page numbers - Where pages numbers are specified they are the page numbers in the service manual unless otherwise specified as the PDF page numbers in Adobe Acrobat Reader. Most of the page numbers referred to are under Chapter 13A - Fuel System in the 1st volume Manual for our cars.

Non-Turbo Focus - As I went thru the manual I realized that because I have a N/A (non-turbo) 1995 3000GT I ended up looking up the sensors in the pages that refer to my type of car. IE: <Up to 1995 Non Turbo models
for Federal and up to 1993 models> as listed by the manual. Still, as I've compared a few of these sensors with other years and the TURBO models, most of the time there is little difference in the look, position, and troubleshooting of these sensors. At least this is something. So I hope it helps.

Service Manual - If you are even looking at 3SI.org at all you shouldn't be doing so without the service manual on CD at your side. The usage of Adobe Acrobat to do "text searches" within the manual is an extremely HUGE time saver and benefit although it may not seem so at first due to all the hours of reading that must be done. So, without the service manual at your side the guide will not make sense and furthermore I reference the manual's page numbers so that you'll go look at the illustrations of the sensors themselves, where they are, what they look like, and further datalogger information that I do not cover here on purpose.

Purpose - This is basically a listing of sensors and what TROUBLSHOOTING behavior is likely the cause of what problems you may be experiencing with regards to idle problems, sputtering at launch/accel, engine threatening to stall when coming to a stop at a red light or stop sign, etc... FYI - I notice the problem more when I am quickly/sharply stopping or starting than I do when I move the accelerator up or down slowly. I almost never notice the problem when I use it slowly.

Likely related sensors:
BAROMETRIC PRESSURE SENSOR........... 91
CAMSHAFT POSITION SENSOR...... 103
CRANKSHAFT POSITION SENSOR ...... 107
Engine Coolant Temperature Sensor . . . . . . . 93
Heated Oxygen .................................. 137
Induction Control Valve Position Sensor . . . . 133
Intake Air Temperature Sensor . . . . . . . . . 88
Throttle Position Sensor . . . . . . . . . . 98
--Sensor (TPS) Adjustment . . . . . . . . . . 57 (put this here cause I recommend doing it)
--Throttle Body (Throttle Valve Area) Cleaning . . . 57 (put this here cause I recommend doing it)
Vehicle Speed Sensor
(Electrical Speedometer Type) . . . . . . . . . . . 119
(Mechanical Speedometer Type) . . . . . . . . 117
Volume Air Flow Sensor. . . . . . . . . . . . . 85

Unlikely related sensors:
EGR Temperature Sensor . . . . 135
(NOTE: Federal spec NON-TURBOs DO NOT HAVE EGR Temp Sensors and to my knowledge are the only 3000GT's that don't have them. Not sure about the Stealth, but from what I've read you are better off blocking EGR with EGR block off plates anyway)
G Sensor
<ACTIVE ECS> .................................. 33B-l 8-l <not in chapter MFI 13A>
<AWD-ABS> ..................................... 35-117 <not in chapter MFI 13A> SEE the manual PDF page 943
Front-impact Sensor ...................................... 52B-68-I <not in chapter MFI 13A> SEE the manual PDF page 1200
Knock Sensor .......................................... 13A-125
<Is In 13A, but I don't think its related. If you've got knock you've got bigger different problems than just sputtering and hesitation.>
Steering Angular Velocity Sensor ........................... 338-18-I <not in chapter MFI 13A>
WheelSpeed Sensor .................................. ..35-113 <not in chapter MFI 13A>

PDF page 195
Barometric Pressure Sensor

OPERATION
The barometric pressure sensor converts the barometric pressure into a voltage and inputs it to
the engine control module, which then corrects the fuel injection, rate, etc. based on the input signal.
The 5 V power in the engine control module is supplied to the barometric pressure sensor. Through
the circuit in the sensor, it is grounded in the engine contrcjl module.
The barometric pressure sensor output voltage which is proportional to the barometric pressure (absolute pressure) is supplied to the engine control module.
TSB Revision; 13A-92 MULTIPORT On-Vehicle Inspection of MFI FUEL INJECTION - Components

TROUBLESHOOTING HINTS
Hint 1: If the barometric pressure sensor is faulty, poor driveability is caused at high altitude, in particular.
Hint 2: If the pressure indication of the barometric pressure sensor drops significantly during high speed
driving, check the air cleaner for clogging.

PDF page 890
Brake Fluid Level Check Sensor
<Doesn't apply to fuel or hesitation related stuff, but I include it because its a sensor>

*Resides in the Brake fluid resevoir and reports brake fluid level of course.

PDF page 329
Camshaft position sensor

OPERATION
The camshaft position sensor senses the top dead center on compression stroke, converts it into
a pulse signal and inputs it to the engine control module, which then controls the fuel injection sequence,
etc. based on the input signal.
Power to the camshaft position sensor is supplied from the MFI relay and is grounded to the body.
The camshaft position sensor generates a pulse signal as it repeatedly connects and disconnects
between 5 V voltage supplied from the engine control module and ground.

TROUBLESHOOTING HINTS
Hint 1: If the camshaft position sensor does not function correctly, correct sequential injection is not
made so that the engine may stall, run irregularly at idle or fail to accelerate normally.
Hint 2: If the sensor outputs a pulse signal when the ignition switch is turned ON (with the engine not running), a faulty camshaft position sensor or engine control module is suspected.

PDF page 330
Crankshaft position sensor

OPERATION
The crankshaft position sensor senses the crank angle (piston position) of each cylinder, converts
it into a pulse signal and inputs it to the engine control module, which then controls the engine
speed and controls the fuel injection timing and ignition timing based on the input signal.
Power to the crankshaft position sensor is supplied from the MFI relay and is grounded to the body.
The crankshaft position sensor generates a pulse signal as it repeatedly connects and disconnects
between 5 V voltage supplied from the engine control module and ground.

TROUBLESHOOTING HINTS
Hint 1: If unexpected shocks are felt during driving or the engine stalls suddenly during idling, shake
the crankshaft position sensor harness. If this causes the engine to stall, poor contact of the
sensor connector is suspected.
Hint 2: If the crankshaft position sensor outputs a pulse signal when the ignition switch is turned ON
(with the engine not running), a faulty crankshaft position sensor or engine control module is
suspected.
Hint 3: If the tachometer reads 0 rpm when the engine that has failed to start is cranked, faulty crankshaft
position sensor or broken timing belt is suspected.
Hint 4: If the tachometer reads 0 rpm when the engine that has failed to start is cranked, the primary
current of the ignition coil is not turned on and off. Therefore, troubles in the ignition circuit and
ignition coil or faulty ignition power transistor is suspected.
Hint 5: If the engine can be run at idle even though the crankshaft position sensor reading is out of
specification, troubles are often in other than the crankshaft position sensor.
[Examples]
(1) Faulty engine coolant temperature sensor
(2) Faulty idle air control motor
(3) Poorly adjusted reference idle speed

PDF page 239
EGR temperature sensor

OPERATION
The EGR temperature sensor converts the temperature of EGR gas downstream from the EGR valve
to voltage and inputs it to the engine control module. The engine control module judges the condition
of the EGR by this signal. If there is abnormal condition, the check engine/malfunction indicator lamp
is turned on to notify the driver.
Five volt power supply in the engine control module is applied to the EGR temperature sensor through
the resistance in the module. This power supply further passes through the EGR temperature sensor,
which is a kind of resistor, and is grounded at the engine control module. The resistance of the
EGR temperature sensor is characterized by a decrease in resistance with an increase of EGR temperature due to increase in quantity of EGR.
EGR temperature sensor terminal voltage increases or decreases with EGR temperature sensor resistance.
Therefore, EGR temperature sensor terminal voltage changes with EGR gas temperature.
The higher the EGR gas temperature, the lower the EGR temperature sensor terminal voltage.

PDF page 197
Engine coolant temperature sensor

OPERATION
The engine coolant temperature sensor converts the engine coolant temperature into a voltage and
inputs it to the engine control module, which then controls the fuel injection rate and fast idle speed
when the engine is cold based on the input signal.
The 5 V power in the engine control module is supplied via a resistor in the module to the engine
coolant temperature sensor. Through the sensor which is a kind of resistor, it is grounded in the
engine control module. The engine coolant temperature sensor resistor has the characteristic of decreasing its resistance decreases as the coolant temperature rises.
The engine coolant temperature sensor terminal voltage increases or decreases as the sensor resistance
increases or decreases. Therefore, the engine coolant temperature sensor terminal voltage changes
with the coolant temperature, decreasing as the temperature rises.

TROUBLESHOOTING HINTS
If the fast idle speed is inadequate or the engine emits dark smoke during engine warm up operation,
the engine coolant temperature sensor is often faulty.

PDF page 189
Volume air flow sensor

OPERATION
*Note: MFI relay; A Harness side connector; Engine control module connector; Engine control module

The volume air flow sensor located in the air cleaner converts the engine intake air volume into
a pulse signal of frequency proportional to the air volume and inputs it to the engine control module,
which then computes the fuel injection rate, etc. based on the input signal.
The volume air flow sensor power is supplied from the MFI relay to the volume air flow sensor and
is grounded in the engine control module. The volume air flow sensor generates a pulse signal as
it repeatedly opens and closes between the 5 V voltage supplied from the engine control module
and ground.

TROUBLESHOOTING HINTS
Hint 1: If the engine stalls occasionally, crank the engine and shake the volume air flow sensor harness.
If the engine stalls, poor contact of the volume air flow sensor connector is suspected.
Hint 2: If the volume air flow sensor output frequency is other than 0 when the ignition switch is turned
on (but not starting the engine), faulty volume air flow sensor or engine control module is suspected.
Hint 3: If the engine can be run idle even though the volume air flow sensor output frequency is out
of specification, troubles are often found in other than the volume air flow sensor itself.
[Examples]
(1) Disturbed volume air flow in the air flow sensor
(Disconnected air duct, clogged air cleaner element)
(2) Poor combustion in the cylinder
(Faulty ignition plug, ignition coil, injector, incorrect compression pressure, etc.)
(3) Air leaking into the intake manifold through gap of gasket, etc.
(4) Loose EGR valve seat

PDF page 221
Vehicle Speed Sensor

(Electrical Speedometer Type) . . . . . . . . . 119 in the manual
(Mechanical Speedometer Type) . . . . . . . . 117 in the manual

OPERATION
Mechanical - The vehicle speed sensor which is located in the speedometer converts the vehicle speed into a pulse signal and inputs it to the engine control module, which then provides the idle speed control,
etc. based on this signal.
The vehicle speed sensor generates the vehicle speed signal by repeatedly opening and closing
between the voltage of about 5 V applied from the engine control module and ground using a reed
switch.

TROUBLESHOOTING HINTS
If there is an open or short circuit in the vehicle speed sensor signal circuit, the engine may stall when
the vehicle is decelerated to stop.
HARNESS INSPECTION

OPERATION
Electrical - The vehicle speed sensor, mounted directly to the speedometer driven gear of the transmission,
converts the vehicle speed to the pulse signal to be input to the engine control module. By this
signal, the engine control module performs idle speed control servo control.
A voltage of approx. 5V is applied from the engine control module to the vehicle speed sensor output
terminal. By turning the power transistor ON and OFF, the vehicle speed sensor generates the pulse
signal.

TROUBLESHOOTING HINTS
Refer to P.l3A-117. *IE: Same as mechanical troubleshooting hints.

PDF page 202
Throttle Position Sensor

OPERATION
The throttle position sensor converts the throttle position opening into a voltage and inputs it to the
engine control module, which then controls the fuel injection based on the input signal.
The 5 V power in the engine control module is supplied to the throttle position sensor. Through
the resistor in the sensor, it is grounded in the engine control module.
As the throttle valve shaft rotates from the idle position to wide open position, the resistance between
the variable resistor terminal of the throttle position sensor and the ground terminal increases. As
a result, the voltage at the throttle position sensor variable resistance terminal also increases.
TROUBLESHOOTING HINTS
Hint 1: The throttle position sensor signal is more important in the control of automatic transaxle than
in the engine control. Shifting shock and other troubles will be caused if this sensor is faulty.
Hint 2: If the output voltage of the throttle position sensor is out of specification, adjust the sensor and
check the voltage again. If there is an evidence of disturbed fixed SAS setting, adjust the fixed
SAS.

PDF page 205
Closed throttle position switch
<Not a sensor, but could be a culprit in related problem behavior>

OPERATION
*Note: Engine control module; A Harness side connector
The closed throttle position switch senses whether the accelerator pedal is depressed or not, converts
it into high/low voltage and inputs the voltage to the engine control module, which then controls
the idle air control motor based on the input signal.
The voltage in the engine control module is applied to the closed throttle position switch through
a resistor. When the accelerator pedal is released, the closed throttle position switch is turned on
to conduct the voltage to ground. This causes the closed throttle position switch terminal voltage
to go low from high.

TROUBLESHOOTING HINTS
If the closed throttle position switch harness and individual part check results are normal but the closed
throttle position switch output is abnormal, the following troubles are suspected.
(1) Poorly adjusted accelerator cable or auto-cruise control cable
(2) Poorly adjusted fixed SAS

PDF page 192
Intake air temperature sensor

OPERATION

The intake air temperature sensor converts the engine intake air temperature into a voltage and
inputs it to the engine control module, which then corrects the fuel injection rate, etc. based on the
input signal.
The 5 V power in the engine control module is supplied via a resistor in the module to the intake
air temperature sensor. Via the sensor which is a kind of resistor, it is grounded in the engine control
module. The intake air temperature sensor resistor has the characteristic of decreasing its resistance
decreases as the intake air temperature rises.
The intake air temperature sensor terminal voltage increases or decreases as the sensor resistance
increases or decreases. Therefore, the intake air temperature sensor terminal voltage changes with
the intake air temperature, decreasing as the temperature rises.

TROUBLESHOOTING HINTS
The intake air temperature sensor senses the intake air temperature in the air cleaner so that it may
indicate a temperature different from outside temperature depending on engine operating state.

PDF page 237
Induction control valve position sensor

OPERATION
The induction control valve position sensor detects the induction control valve opening degree and
converts it into a pulse signal to be input into the engine control module, which provides valve opening
and closing control based on this signal.
The induction control valve position sensor is supplied with 5V power engine control module and
is grounded to the engine control module. A voltage of 5V from the engine control module is impressed
to the two output terminals of the induction control valve position sensor. By opening and closing
the circuit between the output terminal and ground, the induction control valve position sensor generates
the pulse signal.

PDF page 241
Heated oxygen sensor

OPERATION
The heated oxygen sensor senses the oxygen concentration in exhaust gas, converts it into a voltage
and inputs it to the engine control module.
The heated oxygen sensor outputs about 1 V when the air-fuel ratio is richer than the theoretical
ratio and outputs about 0 V when the ratio is leaner (higher oxygen concentration in exhaust gas).
The engine control module controls the fuel injection ratio based on this signal so that the air-fuel
ratio may be kept at the theoretical ratio.
The battery voltage is supplied to the heated oxygen sensor through the MFI relay. Therefore, the
sensor element is heated by the heater so that the heated oxygen’ sensor remains responsive even
when the exhaust temperature is low.
TSB Revision 13A-138 MULTIPORT On-Vehicle Inspection of MFI FUEL INJECTION - Components

TROUBLESHOOTING HINTS
Hint 1: Poor cleaning of exhaust gas will result if the heated oxygen sensor fails.
Hint 2: If the heated oxygen sensor checked good but the sensor output voltage is out of specification,
troubles of parts related to air-fuel ratio control system are suspected.
[Examples]
L)
(1) Faulty injector
(2) Air leaking into the intake manifold through gasket gap, etc.
(3) Faulty volume air flow sensor, intake air temperature sensor, barometric pressure sensor, engine
coolant temperature sensor

PDF page 229
Knock sensor

OPERATION
The knock sensor generates a voltage proportional to the magnitude of cylinder block vibration due to
knocking and inputs it to the engine control module. Based on this signal, the engine control module
provides retard control of the ignition timing.

TROUBLESHOOTING HINTS
When knocking occurs while driving under high-load conditions, the following problems are suspected
in addition to the knock sensor itself.
(1) Inappropriate ignition plug heat range
(2) Inappropriate gasoline
(3) Incorrectly adjusted reference ignition timing