1993 CHEVROLET DYNASTY fuel

dition exists. These messages are displayed on the
center of the instrument panel.For complete EVIC operating instructions, refer to
the Owners Manual provided with the vehicle.
EVIC BUTTON FUNCTIONS
TIME button will display:
² Time of day
² Day of week
² Day of month
² Month of year
² To set HOURS, press TIME button and within four
seconds press the SET button. An arrow will appear
on the display and point to the hours. Press and hold
the SET button to advance the hours or INFO button
to set back the hours.
² To set MINUTES, press TIME button. The arrow
will point to the minutes. Press and hold the SET
button to advance the minutes or INFO button to set
back the minutes.
² To set DAY of WEEK, press TIME button. An ar-
row will appear on the display and point to the Day.
Press and hold the SET button to move the day for-
ward or INFO button to move it backward.
² To set DAY of MONTH, press TIME button. The
arrow will point to Date. Press and hold the SET
button to advance the date or INFO button to move
it backwards.
² To set MONTH of YEAR, press TIME button. The
arrow will point to the Month. Press and hold the
SET button to advance the Month forward or INFO
button to move backward. TEMP button, pressing the Temp button will dis-
play:
² The temperature outside the vehicle
² Vehicle direction define by an eight point compass
If Compass has lost calibration or not receiving
good information from the engine compartment node,
an asterisk (*) will flash on the display and the word
calibrate will appear. Refer to Compass Calibration. FUEL BUTTON, WILL DISPLAY:
² Pressing FUEL button the first time will show, the
estimated number of miles that can be driven with
the remaining fuel. The destination to empty indica-
tion will vary every few seconds as the amount of
fuel and fuel efficiency is calculated. This function
can not be reset.
² Pressing the FUEL button second time; will dis-
play the fuel consumed.
² Pressing the FUEL button third time; will display
the average fuel economy in miles per gallon since
last reset. The display will be updated every 16 sec-
onds.
² Pressing the FUEL button forth time, the current
fuel economy will be displayed. The current fuel
economy will be up updated every two seconds. ²
To reset Fuel consumed, press SET button until
the fuel consumed message is displayed and then
within five seconds press SET button.
² To reset AVERAGE FUEL ECONOMY, press the
FUEL button until average fuel economy is displayed
and within five seconds press SET button. TRIP RESET, press FUEL button and wait four
seconds press the SET button twice. This clears all
trip information and the message Trip Reset will be
displayed. This will occur only if a reset function is
currently being displayed. The reset functions:
² Fuel consumed
² Average fuel economy message
INFO button, will active a MONITORED SYS-
TEMS OK message on display if all monitored sys-
tems are operating properly. If a problem is detected,
the appropriate message will be displayed. SET button, will clear the various functions after
they have been displayed. It is used to enter the
clock set or compass variance modes. This button is
also used to reset certain trip computer functions and
the maintenance reminder message. The EVIC display may be turned off by pressing
the TIME and SET buttons at the same time. Press-
ing the buttons a second time will restore the dis-
play.
EVIC INFORMATION SOURCES
The EVIC monitors information provided by the
body controller, engine compartment node and pow-
ertrain control module. Refer to Body Diagnostic Test
Procedure Manual for test procedures. The Body Controller is a micro-controller unit
which, informs the EVIC via the CCD bus of:
² Time of day
² Day of week
² Day of month
² Month of year
² Fuel range
² Fuel consumed
² Fuel efficiency
² Warning messages as noted in Fig. 3.
The Engine Compartment Node is a microcomputer
controlled unit which, informs the EVIC via the CCD
bus of:
² Outside temperature
² Compass direction
THE FOLLOWING ARE WARNING MESSAGES:
² Low brake fluid
² Low coolant level
² Low engine oil level
The powertrain control module is a microcomputer
controlled unit which, informs the EVIC via the CCD
bus of the following warning messages:
² Engine temperature high
² Voltage improper
8C - 14 OVERHEAD CONSOLE Ä

VISUAL MESSAGES
Following are the visual messages and the condi-
tions under which, the messages will be given:
² Keys in ignition
² Exterior lamps on
These messages will appear if the conditions are
present and the driver's door is open while the igni-
tion switch is in the OFF, LOCK, or ACC positions.
A tone will sound until the condition is corrected or
the door is closed.
² Passenger door ajar
² Driver door ajar
² Trunk ajar
² Park brake engaged
² Right rear door ajar
² Left rear door ajar
These messages will appear if a condition is de-
tected after the vehicle is in motion. When the con-
dition is corrected, a short tone will sound to
acknowledge the action. LOW OIL PRESSURE
If this message is displayed while the vehicle is at
cruising speeds, immediate attention is required. If
this message appears at idle speed, increase the idle
speed and the message should go off. If the message
remains on, immediate attention is required. ENGINE TEMP CRITICAL
This message appears when a sensor has deter-
mined that the engine coolant is overheating. If this
message comes on and stays on, immediate action is
required. COOLANT LEVEL LOW
LOW FUEL LEVEL
LOW BRAKE FLUID WASHER FLUID LOW
These messages will appear if a continuous warn-
ing condition is detected while the engine is running.
Inspection is required. To clear this message from
the display, after the condition is corrected, the igni-
tion switch must be turned OFF. CHECK TRANS
This message will appear if a continuous warning
condition is detected while the engine is running. Im-
mediate attention is recommended. To clear this mes-
sage from the display, after the condition has been
corrected, the ignition switch must be turned OFF. VOLTAGE IMPROPER
This message will appear if a continuous warning
condition is detected. Immediate attention is re-
quired. To clear this message from the display, after
the condition has been corrected, the ignition switch
must be turned OFF. TURN SIGNAL ON
This message will appear if the turn signal is left
on while vehicle speed is over 15 mph and the vehi-
cle has traveled over one-half mile. FASTEN SEAT BELTS
An intermittent chime tone will sound for several
seconds if the seat belt is not fastened. CHK ENGINE OIL LEVEL
If this message is delivered, a check of the engine
oil dipstick is suggested. To clear this message, after
the condition is corrected, the ignition switch must
be turned OFF. HEADLAMP OUT
BRAKE LAMP OUT
TAIL LAMP OUT
These conditions are monitored only when the
lamps are on. The message will remain, even after
the lamp is replaced, until the lamp is turned on and
operates. SERVICE REMINDER
The maintenance reminder statement is pro-
grammed to provide general information only. Refer
to Group 0, Lubrication & Maintenance for specific
vehicle requirements. The service reminder message is displayed at 7,500
miles or 12 months intervals, which ever comes first. MONITORED SYSTEMS OK
If there is no warning condition to report, the mes-
sage Monitored Systems OK is displayed (Fig. 3).
ENGINE COMPARTMENT NODE (ECN)
The Engine Compartment Node is a microcomputer
controlled unit which, informs the Electronic Vehicle
Information Center (EVIC) via the CCD bus of:
² Outside temperature
² Compass direction
and the following warning messages:
² Low Brake Fluid
² Low Coolant Level
² Low Engine Oil Level
Fig. 3 EVIC Messages and Sensors
Ä OVERHEAD CONSOLE 8C - 15

IGNITION SYSTEMS
CONTENTS
page page
2.2L TBI, 2.5L TBI, 2.5L MPI AND 3.0L IGNITION SYSTEMSÐDIAGNOSTIC PROCEDURES
..... 11
2.2L TBI, 2.5L TBI, 2.5L MPI AND 3.0L IGNI- TION SYSTEMSÐSERVICE PROCEDURES . 14
2.2L TBI, 2.5L TBI, 2.5L MPI AND 3.0L IGNI- TION SYSTEMSÐSYSTEM OPERATION .... 1
2.2L TURBO III, 3.3L AND 3.8L IGNITION SYSTEMÐDIAGNOSTIC PROCEDURES
.... 35
2.2L TURBO III, 3.3L AND 3.8L IGNITION SYSTEMÐSYSTEM OPERATION ......... 24
2.2L TURBO III, 3.3L AND 3.8L IGNITION SYSTEMSÐSERVICE PROCEDURES ...... 39
IGNITION SWITCH ...................... 45
SPECIFICATIONS ....................... 47
GENERAL INFORMATION
Throughout this group, references are made to par-
ticular vehicles by letter designation. A chart ex-
plaining the designations appears in the Introduction
Section of this manual.
2.2L TBI, 2.5L TBI, 2.5L MPI AND 3.0L IGNITION SYSTEMSÐSYSTEM OPERATION
INDEX
page page
Auto Shutdown (ASD) Relay and Fuel Pump Relay . 8
Coolant Temperature Sensor ................. 7
Distributor Cap ........................... 1
Distributor Pick-UpÐ3.0L Engine .............. 7
Distributor Pick-UpÐPCM Input ............... 6
General Information ........................ 1 Ignition Coil
.............................. 9
Manifold Absolute Pressure (MAP) Sensor ...... 8
Powertrain Control Module (PCM) ............. 6
Rotor .................................. 2
Spark Plug Cables ........................ 2
Spark Plugs ............................. 3
GENERAL INFORMATION
This section describes the ignition systems of the
2.2L TBI, 2.5L TBI, 2.5L MPI (flexible fuel AA-body)
and 3.0L engines. The Fuel Injection sections of Group 14 explain On
Board Diagnostics. Group 0, Lubrication and Maintenance, contains
general maintenance information for ignition related
items. The Owner's Manual also contains mainte-
nance information.
DISTRIBUTOR CAP
Remove the distributor cap and inspect the inside
for flash over, cracking of carbon button, lack of
spring tension on carbon button, cracking of cap, and
burned, worn terminals (Fig. 1). Also check for bro-
ken distributor cap towers. If any of these conditions
are present the distributor cap and/or cables should
be replaced. When replacing the distributor cap, transfer cables
from the original cap to the new cap one at a time.
Ensure each cable is installed into the corresponding tower of the new cap. Fully seat the wires into the
towers. If necessary, refer to the appropriate engine
firing order diagram (Fig. 2 or Fig. 3).
Fig. 1 Distributor Cap Inspection
Ä
IGNITION SYSTEMS 8D - 1

When testing secondary cables for punctures and
cracks with an oscilloscope follow the equipment
manufacturers instructions. If an oscilloscope is not available, secondary cables
can be tested as follows:
CAUTION: Do not leave any one spark plug cable
disconnected any longer than necessary during test-
ing. Excessive heat could damage the catalytic con-
verter. Total test time must not exceed ten minutes.
(a) With the engine not running, connect one end
of a test probe to a good ground. Use a probe made of
insulated wire with insulated alligator clips on each
end. (b) With engine running, move test probe along
entire length of all cables (approximately 0 to 1/8
inch gap). If punctures or cracks are present there
will be a noticeable spark jump from the faulty area
to the probe. Check the coil cable the same way.
Replace cracked, leaking or faulty cables.
When replacing cables, install the new high
tension cable and nipple assembly over cap or
coil tower. When entering the terminal into the
tower, push lightly, then pinch the large diam-
eter of nipple to release air trapped between the
nipple and tower. Continue pushing on the cable
and nipple until cables are properly seated in the
cap towers. A snap should be heard as terminal
goes into place. Use the same procedure to install cable in coil tower.
Wipe the spark plug insulator clean before reinstalling
cable and cover. Use the following procedure when removing the high
tension cable from the spark plug. First, remove the
cable from the retaining bracket. Then grasp the ter-
minal as close as possible to the spark plug. Rotate the
cover and pull the cable straight back. Pulling on the
cable itself will damage the conductor and termi-
nal connection. Do not use pliers and do not pull
the cable at an angle. Doing so will damage the
insulation, cable terminal or the spark plug in-
sulator. Wipe spark plug insulator clean before
reinstalling cable and cover. Resistance type cable is identified by the words
Electronic Suppression printed on the cable jacket.
Use an ohmmeter to check resistance type cable for
open circuits, loose terminals or high resistance as
follows: (a) Remove cable from spark plug.
(b) Lift distributor cap from distributor with
cables intact. Do not remove cables from cap. The
cables must be removed from the spark plugs. (c) Connect the ohmmeter between spark plug end
terminal and the corresponding electrode inside the
cap, make sure ohmmeter probes are in good contact.
Resistance should be within tolerance shown in the cable resistance chart. If resistance is
not within tolerance, remove cable at cap tower
and check the cable. If resistance is still not within
tolerance, replace cable assembly. Test all spark
plug cables in same manner.
To test coil to distributor cap high tension cable,
remove distributor cap with the cable intact. Do not
remove cable from the cap. Connect the ohmmeter
between center contact in the cap and remove the ca-
ble at coil tower and check cable resistance. If resis-
tance is not within tolerance, replace the cable.
SPARK PLUGS
Resistor spark plugs are used in all engines and
have resistance values of 6,000 to 20,000 ohms when
checked with at least a 1000 volt tester. Remove the spark plugs and examine them for
burned electrodes and fouled, cracked or broken por-
celain insulators. Keep plugs arranged in the order
in which they were removed from the engine. An iso-
lated plug displaying an abnormal condition indi-
cates that a problem exists in the corresponding
cylinder. Replace spark plugs at the intervals recom-
mended in Group O. Undamaged low milage spark plugs can be cleaned
and reused. Refer to the Spark Plug Condition sec-
tion of this group. After cleaning, file the center elec-
trode flat with a small point file or jewelers file.
Adjust the gap between the electrodes (Fig. 6) to the
dimensions specified in the chart at the end of this
section. Always tighten spark plugs to the specified torque.
Over tightening can cause distortion and change
spark plug gap. Tighten spark plugs to 28 N Im (20 ft.
lbs.) torque.
SPARK PLUG CONDITION
NORMAL OPERATING CONDITIONS
The few deposits present will be probably light tan
or slightly gray in color with most grades of commer-
cial gasoline (Fig. 7). There will not be evidence of
electrode burning. Gap growth will not average more
than approximately 0.025 mm (.001 in) per 1600 km
(1000 miles) of operation. Spark plugs that have nor-
mal wear can usually be cleaned, have the electrodes
filed and regapped, and then reinstalled. Some fuel refiners in several areas of the United
States have introduced a manganese additive (MMT)
CABLE RESISTANCE CHART
Ä IGNITION SYSTEMS 8D - 3

for unleaded fuel. During combustion, fuel with
MMT coats the entire tip of the spark plug with a
rust color deposit. The rust color deposits could be
misdiagnosed as being caused by coolant in the com-
bustion chamber. MMT deposits do not affect spark
plug performance.
COLD FOULING (CARBON FOULING)
Cold fouling is sometimes referred to as carbon
fouling. The deposits that cause cold fouling are ba-
sically carbon (Fig. 7). A dry, black deposit on one or
two plugs in a set may be caused by sticking valves
or defective spark plug cables. Cold (carbon) fouling
of the entire set may be caused by a clogged air
cleaner. Cold fouling is normal after short operating periods.
The spark plugs do not reach a high enough operating
temperature during short operating periods.
WET FOULING
A spark plug that is coated with excessive wet fuel or
oil is wet fouled. In older engines, wet fouling can be
caused by worn rings or excessive cylinder wear.
Break-in fouling of new engines may occur be-
fore normal oil control is achieved. In new or
recently overhauled engines, wet fouled spark
plugs can be usually be cleaned and reinstalled.
OIL OR ASH ENCRUSTED
If one or more plugs are oil or oil ash encrusted,
engine oil is entering the combustion chambers (Fig. 8).
Evaluate the engine to determine the cause.
HIGH SPEED MISS When replacing spark plugs because of a high speed
miss condition; wide open throttle operation
should be avoided for approximately 80 km (50
miles) after installation of new plugs. This will
allow deposit shifting in the combustion chamber to
take place gradually and avoid plug destroying splash
fouling shortly after the plug change.
ELECTRODE GAP BRIDGING
Loose deposits in the combustion chamber can cause
electrode gap bridging. The deposits accumulate on the
spark plugs during continuous stop-and-go driving.
When the engine is suddenly subjected to a high torque
load, the deposits partially liquefy and bridge the gap
between the electrodes
Fig. 6 Setting Spark Plug Electrode GapÐTypical
Fig. 7 Normal Operation and Cold (Carbon) FoulingFig. 8 Oil or Ash Encrusted
8D - 4 IGNITION SYSTEMS Ä

(Fig. 9). This short circuits the electrodes. Spark
plugs with electrode gap bridging can be cleaned us-
ing standard procedures.
SCAVENGER DEPOSITS Fuel scavenger deposits may be either white or yel-
low (Fig. 10). They may appear to be harmful, but
are a normal condition caused by chemical additives
in certain fuels. These additives are designed to
change the chemical nature of deposits and decrease
spark plug misfire tendencies. Accumulation on the
ground electrode and shell area may be heavy but
the deposits are easily removed. Spark plugs with
scavenger deposits can be considered normal in con-
dition and be cleaned using standard procedures.
CHIPPED ELECTRODE INSULATOR A chipped electrode insulator usually results from
bending the center electrode while adjusting the
spark plug electrode gap. Under certain conditions,
severe detonation also can separate the insulator
from the center electrode (Fig. 11). Replace spark
plugs with chipped electrode insulators. PREIGNITION DAMAGE
Excessive combustion chamber temperature can
cause preignition damage. The center electrode dis-
solves first and the ground electrode dissolves some-
what later (Fig. 12). Insulators appear relatively
deposit free. Determine if the spark plug has the cor-
rect heat range rating for the engine, if ignition tim-
ing is over advanced or if other operating conditions
are causing engine overheating. The heat range rat-
ing refers to the operating temperature of a particu-
lar type spark plug. Spark plugs are designed to
operate within specific temperature ranges depend-
ing upon the thickness and length of the center elec-
trode and porcelain insulator.
SPARK PLUG OVERHEATING Overheating is indicated by a white or gray center
electrode insulator that also appears blistered (Fig.
13). The increase in electrode gap will be consider-
ably in excess of 0.001 in per 1000 miles of operation.
This suggests that a plug with a cooler heat range
rating should be used. Over advanced ignition tim-
Fig. 9 Electrode Gap Bridging
Fig. 10 Scavenger Deposits
Fig. 11 Chipped Electrode Insulator
Fig. 12 Preignition Damage
Ä IGNITION SYSTEMS 8D - 5

ing, detonation and cooling system malfunctions also
can cause spark plug overheating.
SPARK PLUG SERVICE
When replacing the spark plug and coil cables,
route the cables correctly and secure them in the ap-
propriate retainers. Failure to route the cables prop-
erly can cause the radio to reproduce ignition noise,
cross ignition of the spark plugs or short circuit the
cables to ground.
SPARK PLUG REMOVAL
Always remove the spark plug cable by grasping at
the spark plug boot turning, the boot 1/2 turn and
pulling straight back in a steady motion. (1) Prior to removing the spark plug spray com-
pressed air around the spark plug hole and the area
around the spark plug. (2) Remove the spark plug using a quality socket
with a rubber or foam insert. (3) Inspect the spark plug condition. Refer to
Spark Plug Condition in this section.
SPARK PLUG GAP ADJUSTMENT Check the spark plug gap with a gap gauge. If the
gap is not correct, adjust it by bending the ground
electrode (Fig. 6).
SPARK PLUG INSTALLATION (1) To avoid cross threading, start the spark plug
into the cylinder head by hand. (2) Tighten spark plugs to 28 N Im (20 ft. lbs.)
torque. (3) Install spark plug cables over spark plugs.
POWERTRAIN CONTROL MODULE (PCM)
The ignition system is regulated by the powertrain
control module (PCM) (Fig. 14). The PCM supplies
battery voltage to the ignition coil through the Auto
Shutdown (ASD) Relay. The PCM also controls the
ground circuit for the ignition coil. By switching the ground path for the coil on and off, the PCM adjusts
ignition timing to meet changing engine operating
conditions.
During the crank-start period the PCM advances
ignition timing a set amount. During engine opera-
tion, the amount of spark advance provided by the
PCM is determined by these input factors:
² coolant temperature
² engine RPM
² available manifold vacuum
The PCM also regulates the fuel injection system.
Refer to the Fuel Injection sections of Group 14.
DISTRIBUTOR PICK-UPÐPCM INPUT
The engine speed input is supplied to the power-
train control module (PCM) by the distributor pick-
up. The distributor pick-up is a Hall Effect device
(Fig. 15 or Fig. 16).
A shutter (sometimes referred to as an interrupter)
is attached to the distributor shaft. The shutter con-
tains four blades, one per engine cylinder. A switch
plate is mounted to the distributor housing above the
shutter. The switch plate contains the distributor
Fig. 14 Powertrain control module (PCM)
Fig. 15 DistributorÐ2.2L and 2.5L TBI Engines
Fig. 13 Spark Plug Overheating
8D - 6 IGNITION SYSTEMS Ä

pick-up (a Hall Effect device and magnet) through
which the shutter blades rotate. As the shutter
blades pass through the pick-up, they interrupt the
magnetic field. The Hall effect device in the pick-up
senses the change in the magnetic field and switches
on and off (which creates pulses), generating the in-
put signal to the PCM. The PCM calculates engine
speed through the number of pulses generated. On 2.5L MPI (flexible fuel AA-Body) engines, one
of the shutter blades has a window cut into it. The
PCM determines injector synchronization from the
window. Also, the PCM uses the input for detonation
control.
DISTRIBUTOR PICK-UPÐ3.0L ENGINE
The distributor pick-up provides two inputs to the
powertrain control module (PCM). From one input
the PCM determines RPM (engine speed). From the
other input it derives crankshaft position. The PCM
regulates injector synchronization and adjusts igni-
tion timing and engine speed based on these inputs. The distributor pick-up contains two signal gener-
ators. The pick-up unit consists of 2 light emitting
diodes (LED), 2 photo diodes, and a separate timing
disk. The timing disk contains two sets of slots. Each
set of slots rotates between a light emitting diode
and a photo diode (Fig. 17). The inner set contains 6
large slots, one for each cylinder. The outer set con-
tains several smaller slots. The outer set of slots on the rotating disk repre-
sents 2 degrees of crankshaft rotation. Up to 1200
engine RPM, the PCM uses the input from the outer
set of slots to increase ignition timing accuracy. The outer set of slots contains a 10 degree flat spot.
This area is not slotted (Fig. 17). The flat spot tells
the PCM that the next piston at TDC will be number
6. Each piston's position is referenced by one of the
six inner slots (Fig. 18). As each slot on the timing disk passes between the
diodes, they interrupt the beam from the light emit-
ting diode. This creates an alternating voltage in
each photo diode which is converted into on-off
pulses. The pulses are the input to the PCM. During cranking, the PCM cannot determine which
cylinder will be at TDC until the 10 degree flat spot
on the outer set of slots rotates through the optical
unit. Once the flat spot is detected, the PCM knows
piston number 6 will be the next piston at TDC. Since the disk rotates at half crankshaft speed, it
may take up to 2 engine revolutions during cranking
before the PCM determines the position of piston
number 6. For this reason the PCM energizes all six
injectors at the same time until it senses the position
of piston number 6.
COOLANT TEMPERATURE SENSOR
On 2.2L TBI, 2.5L TBI and 2.5L MPI engines, the
coolant temperature sensor is installed behind the
thermostat housing and ignition coil in the hot box
(Fig. 19). On 3.0L engines the sensor is located next
Fig. 16 DistributorÐ2.5L MPI (Flexible Fuel AA-Body)Fig. 17 Distributor Pick-upÐ3.0L Engine
Fig. 18 Inner and Outer Slots of Rotating DiskÐ3.0L Engine
Ä IGNITION SYSTEMS 8D - 7