1991 MITSUBISHI MONTERO ECO mode
[x] Cancel search: ECO modePage 1216 of 1333
or alcohol
Intermittent ECM ground Test ECM ground
connection for
resistance
Restricted air cleaner Replace air cleaner
Restricted exhaust system Test for exhaust
manifold back
pressure
Poor MAF sensor signal Check leakage
between sensor and
manifold
Poor VSS signal If tester for ALCL
hook-up is available
check that VSS
reading matches
speedometer
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Ping or Knock on Poor Knock sensor signal Test for shorted or
Acceleration open sensor or
circuit
Poor Baro sensor signal Test for shorted or
open sensor or
circuit
Improper ignition timing See VEHICLE EMISSION
CONTROL LABEL (where
applicable)
Check for engine Low coolant, loose
overheating problems belts or electric
cooling fan
inoperative
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NOTE: For additional electronic fuel injection trouble shooting
information, see the appropriate article in the ENGINE
PERFORMANCE section (not all vehicles have Computer Engine
Control articles). Information is provided there for
diagnosing fuel system problems on vehicles with electronic
fuel injection.
IGNITION SYSTEM TROUBLE SHOOTING
NOTE: This is GENERAL information. This article is not intended
to be specific to any unique situation or individual vehicle
configuration. The purpose of this Trouble Shooting
information is to provide a list of common causes to
problem symptoms. For model-specific Trouble Shooting,
refer to SUBJECT, DIAGNOSTIC, or TESTING articles available
in the section(s) you are accessing.
Ignition Secondary Trouble Shooting Chart
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START: Visually inspect Spark Plug Wires, Coil Wires,
Plug Wire Boots, Rotor, and Distributor Cap for
signs of damage.
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OK NOT OK
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* Check air Gap of the Pick-Up * Check resistance of ballast
coil in the distributor. resistor (if used) for the
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correct resistance value.
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* Check Pick-Up coil for * Adjust or replace as
correct resistance value. necessary.
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* Replace Pick-Up coil if * Check control module for
not to specification. good ground connections.
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OK
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* If vehicle fails to run at this point, go to
the appropriate article in the ENGINE
PERFORMANCE section.
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* Check wires from the battery/ * Replace ballast resistor
ignition switch to the coil. if the measured resistance
Also check the coil primary value is not within
and secondary resistance. specification.
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STARTER TROUBLE SHOOTING
NOTE: This is GENERAL information. This article is not intended
to be specific to any unique situation or individual vehicle
configuration. The purpose of this Trouble Shooting
information is to provide a list of common causes to
problem symptoms. For model-specific Trouble Shooting,
refer to SUBJECT, DIAGNOSTIC, or TESTING articles available
in the section(s) you are accessing.
BASIC STARTER TROUBLE SHOOTING CHART
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CONDITION POSSIBLE CAUSE CORRECTION \
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Starter Fails Dead battery or bad Check battery charge
to Operate connections between and all wires and
starter and battery connections to starter
Page 1267 of 1333
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WAVEFO RM S - IN JE C TO R P A TTE R N T U TO RIA L
1991 M it s u bis h i M onte ro
GENERAL INFORMATION
Waveforms - Injector Pattern Tutorial
* PLEASE READ THIS FIRST *
NOTE: This article is intended for general information purposes
only. This information may not apply to all makes and models.
PURPOSE OF THIS ARTICLE
Learning how to interpret injector drive patterns from a Lab
Scope can be like learning ignition patterns all over again. This
article exists to ease you into becoming a skilled injector pattern
interpreter.
You will learn:
* How a DVOM and noid light fall short of a lab scope.
* The two types of injector driver circuits, voltage controlled
& current controlled.
* The two ways injector circuits can be wired, constant
ground/switched power & constant power/switched ground.
* The two different pattern types you can use to diagnose with,
voltage & current.
* All the valuable details injector patterns can reveal.
SCOPE OF THIS ARTICLE
This is NOT a manufacturer specific article. All different
types of systems are covered here, regardless of the specific
year/make/model/engine.
The reason for such broad coverage is because there are only
a few basic ways to operate a solenoid-type injector. By understanding
the fundamental principles, you will understand all the major points
of injector patterns you encounter. Of course there are minor
differences in each specific system, but that is where a waveform
library helps out.
If this is confusing, consider a secondary ignition pattern.
Even though there are many different implementations, each still has
a primary voltage turn-on, firing line, spark line, etc.
If specific waveforms are available in On Demand for the
engine and vehicle you are working on, you will find them in the
Engine Performance section under the Engine Performance category.
IS A LAB SCOPE NECESSARY?
INTRODUCTION
You probably have several tools at your disposal to diagnose
injector circuits. But you might have questioned "Is a lab scope
necessary to do a thorough job, or will a set of noid lights and a
multifunction DVOM do just as well?"
In the following text, we are going to look at what noid
lights and DVOMs do best, do not do very well, and when they can
mislead you. As you might suspect, the lab scope, with its ability to
look inside an active circuit, comes to the rescue by answering for
the deficiencies of these other tools.
OVERVIEW OF NOID LIGHT
Page 1270 of 1333
full load. The Kent-Moore J-39021 is such a tool, though there are
others. The Kent-Moore costs around $240 at the time of this writing
and works on many different manufacturer's systems.
The second method is to use a lab scope. Remember, a lab
scope allows you to see the regular operation of a circuit in real
time. If an injector is having an short or intermittent short, the lab
scope will show it.
Checking Available Voltage At the Injector
Verifying a fuel injector has the proper voltage to operate
correctly is good diagnostic technique. Finding an open circuit on the
feed circuit like a broken wire or connector is an accurate check with
a DVOM. Unfortunately, finding an intermittent or excessive resistance
problem with a DVOM is unreliable.
Let's explore this drawback. Remember that a voltage drop due
to excessive resistance will only occur when a circuit is operating?
Since the injector circuit is only operating for a few milliseconds at
a time, a DVOM will only see a potential fault for a few milliseconds.
The remaining 90+% of the time the unloaded injector circuit will show
normal battery voltage.
Since DVOMs update their display roughly two to five times a
second, all measurements in between are averaged. Because a potential
voltage drop is visible for such a small amount of time, it gets
"averaged out", causing you to miss it.
Only a DVOM that has a "min-max" function that checks EVERY
MILLISECOND will catch this fault consistently (if used in that mode).\
The Fluke 87 among others has this capability.
A "min-max" DVOM with a lower frequency of checking (100
millisecond) can miss the fault because it will probably check when
the injector is not on. This is especially true with current
controlled driver circuits. The Fluke 88, among others fall into this
category.
Outside of using a Fluke 87 (or equivalent) in the 1 mS "min-\
max" mode, the only way to catch a voltage drop fault is with a lab
scope. You will be able to see a voltage drop as it happens.
One final note. It is important to be aware that an injector
circuit with a solenoid resistor will always show a voltage drop when
the circuit is energized. This is somewhat obvious and normal; it is a
designed-in voltage drop. What can be unexpected is what we already
covered--a voltage drop disappears when the circuit is unloaded. The
unloaded injector circuit will show normal battery voltage at the
injector. Remember this and do not get confused.
Checking Injector On-Time With Built-In Function
Several DVOMs have a feature that allows them to measure
injector on-time (mS pulse width). While they are accurate and fast to\
hookup, they have three limitations you should be aware of:
* They only work on voltage controlled injector drivers (e.g
"Saturated Switch"), NOT on current controlled injector
drivers (e.g. "Peak & Hold").
* A few unusual conditions can cause inaccurate readings.
* Varying engine speeds can result in inaccurate readings.
Regarding the first limitation, DVOMs need a well-defined
injector pulse in order to determine when the injector turns ON and
OFF. Voltage controlled drivers provide this because of their simple
switch-like operation. They completely close the circuit for the
entire duration of the pulse. This is easy for the DVOM to interpret.
The other type of driver, the current controlled type, start
off well by completely closing the circuit (until the injector pintle
opens), but then they throttle back the voltage/current for the
duration of the pulse. The DVOM understands the beginning of the pulse