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TomcoTechtips

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TM ISSUE 6

FORD EEC-IV QUICK TEST

How to read trouble codes on Ford's EEC-IV

QUICK TEST STEPS

1. Visual Check & Vehicle Preparation

2. Equipment Hookup

3. Key On Engine Off Self-Test

4. Computed Timing Check

5. Engine Running Self-Test

6. Continuous Self-Test

SELF TEST CONNECTOR

LOCATED IN ENGINE COMPARTMENT

VOLTMETER

VISUAL CHECK

(Very important - These

Basic checks solve over

50% of problems)

1. Inspect the air cleaner and inlet duct. Correct if necessary.

2. Check all engine vacuum hoses for damage, leaks, cracks, blockage, proper routing, etc. - Very important if customer reports recent engine work.

3. Check EEC-IV system wiring harness for proper connections, bent or broken pins, corrosion, loose wires, proper routing, etc.

4. Check the engine coolant for proper level.

5. Make all necessary repairs before continuing with QUICK TEST.

VEHICLE PREPARATION

1. Perform ALL safety steps required to start and run vehicle tests.

2. Turn off ALL electrical loads - radios, lights, A/C-heater blower fans, etc.

3. Start engine and run until at operat-

ing temperature.

4. Turn engine off and proceed.

SELF-TEST DESCRIPTION

The Self-Test is divided into three sections. Key On Engine Off, Engine

Running, and Continuous Self-Test.

The computer stores the Self-Test program in its permanent memory. When activated, it checks the EEC-IV system by testing its memory integrity

SELF TEST

OUTPUT

2" JUMPER

SELF TEST

CONN.

SELF TEST

INPUT

Fig. #2

2" JUMPER

Fig. #1 and processing capability, and verifies that various sensors and actuators are connected and operating properly.

Most automotive computer scanners have Ford EEC-IV adaptors. They usually have a digital type read out of codes and prompting messages to help you along. Follow their instructions.

An inexpensive analog (pointer type) volt meter with a 12v scale can also be used.

Find the Self-Test connector. It can be in various locations in the engine compartment. It's appearance is the same - a large six connector output and small single input connector, see Fig. #1.

KEY ON ENGINE OFF

SELF-TEST

At this time, a test of the EEC-IV system is conducted with power applied and engine at rest.

For Self-Test to detect errors in the

Key On Engine Off Self-Test mode, the fault must be present at the time of testing. For intermittents, refer to Continuous Memory Codes.

CONTINUOUS MEMORY

CODES

Continuous Memory Codes are issued as a result of information stored while the vehicle was in normal operation during the last 40 starts. These codes are displayed after the separator code 10.

These codes should be used for diagnosis only when Key On Engine Off and

Engine Running Self-Tests result in pass or "ok" code 11.

Fig. #3

TOMCO TECH TIP #6

EQUIPMENT HOOKUP

USING AN ANALOG VOLT/OHM METER

(VOM)

1. Turn the ignition key off.

2. Two 2" long jumper wires with 1/4" male spade type connections on

both ends - is helpful in making good electrical contact - see Fig.

#1. Set theVOM on a DC voltage range to read from 0 to 15 volts.

3. Connect the VOM from the Battery

+ terminal to the Self-Test Output pin of the large Self-Test connec

tor. Use one of the connectors for a better electrical connection fig. #2.

4. Connect a timing light.

1/2

SECOND

PAUSE

1 NEEDLE PULSE (SWEEP) + 1 NEEDLE (SWEEP) =

2 SECOND PAUSE BETWEEN DIGITS

1 NEEDLE PULSE

(SWEEP) +

FOR 1/2 SECOND

1/2

SECOND

PAUSE

1 NEEDLE PULSE

(SWEEP) +

FOR 1/2 SECOND

2 NEEDLE PULSE

(SWEEP) FOR

1ST DIGIT

= 23

1/2

SECOND

PAUSE

1 NEEDLE PULSE

(SWEEP) =

FOR 1/2 SECOND

3 NEEDLE PULSE

(SWEEP) FOR

2ND DIGIT

USING THE "CHECK

ENGINE" LIGHT (MIL)

On some late models the check engine light will flash codes in a similar manner as on GM vehicles. No special equipment hookup is required on these cars.

4 SECOND PAUSE BETWEEN SERVICE CODES,

WHEN MORE THAN ONE CODE IS INDICATED

HOW TO RUN THE KEY ON

ENGINE OFF SELF-TEST

DO

* Place ignition key in the ON position.

* Activate Self-Test.

Analog VOM: Jumper STI to SIG

RTN at the Self-Test connectors.

* Record all service codes displayed.

DON'T

* Depress throttle during Key On

Engine Off Self-Test.

On all vehicles equipped with a 4.9L

engine, the clutch must be depressed during the Key On Engine Off Self-

Test.

On these models during Self-

Test a service code is reported by the

"Check Engine" Light flashing. A singledigit number of three will be reported by three flashes. To access codes using the check engine light use the same steps used in hooking up the Self-Test connector as with the voltmeter must be followed.

ENGINE RUNNING SELF-

TEST

At this time, a test of the EEC-IV system is conducted with the engine running. The sensors are checked under actual operating conditions and at normal operating temperatures. The actuators are exercised and checked for corresponding results.

READING CODES -

ANALOG VOLTMETER

A service code on the analog voltmeter will represent itself as a pulsing or sweeping movement of the voltmeter's needle. For example: The Self-

Tests service code of 2-3 will appear on the voltmeter as two needle pulses

(sweeps), then, after a two-second pause, the needle will pulse (sweep) three times.

The continuous Memory Codes are separated from the Key On Engine

Off codes by a six second delay, a single half-second sweep, and another six-second delay. See Fig. #3.

ENGINE IDENTIFICATION

CODES (ID CODES)

Engine ID codes are issued at the beginning of the Engine Running

Self-Test and are one-digit numbers represented by the number of pulses sent out. The engine ID code is equal to onehalf the number of engine cylinders (i.e.

2 pulses = 4 cylinders). These codes are used to verify that the proper processor is installed and that the Self-Test has been entered.

READING CODES -

"CHECK ENGINE" LIGHT

The "Check Engine" Light on the front dash panel on some models will remain on when a hard fault (open or short circuit) is present.

ENGINE RUNNING SELF-

TEST

On vehicles equipped with the

Brake On/Off Switch (BOO),the brake pedal MUST be depressed and released

AFTER the ID code.

Fig. #3

On vehicles equipped with the

Power Steering Pressure Switch (PSPS),

The steering wheel must be turned at least one-half turn and released within 1 to 2 seconds after the ID code.

HOW TO RUN THE ENGINE

RUNNING SELF-TEST

DO

* Deactivate Self-Test. Remove Self-

Test input jumper.

* Start and run engine at 2,000 rpm for two minutes. This action warms up the EGO sensor.

* Turn engine off, wait 10 seconds.

* Start engine.

* Activate Self-Test. Plug Self-Test jumper back in.

* After the ID code, depress and release the brake pedal if appropriate. See Special Note Above.

* After the ID code, within 1 to 2 seconds, turn the steering wheel at least one-half turn and then release it, if appropriate. See Special Note

Above.

* If a dynamic response code occurs, perform a brief wide-open throttle

(WOT).

* Record all service codes displayed.

DON'T

* Depress the throttle unless a

Dynamic Response Code is displayed.

DYNAMIC RESPONSE

CHECK

The dynamic response check verifies the movement of the TP, VAF and

MAP sensors during the brief Wide-Open

Throttle (WOT) performed during the

Engine Running Self-Test. The signal for the operator to perform the brief WOT is a single pulse on the voltmeter.

COMPUTED TIMING

CHECK

If the "Check Engine" Light (MIL) is on, do not run Quick Test timing check.

Verify Key On Engine Off Self-Test is a

PASS (code).

Self-Test timing is equal to Base

Timing plus 20 degrees BTDC + 3 degrees (see VECI decal for correct base timing).

Example:

If base timing is 10 degrees BTDC,

Self-Test timing is equal to: 10 degrees +

20 degrees = 30 degrees BTDC + 3 degrees or 27 degrees to 33 degrees

BTDC.

HOW TO RUN QUICK TEST

TIMING CHECK

1.

Turn the key off and wait 10 seconds.

2.

Start engine.

3.

Activate Engine Running Self-Test.

4.

Check timing after the last service code has been displayed. The timing will remain fixed for two minutes, unless Self-Test is deactivated.

DIAGNOSTIC AIDS

CONTINUOUS MONITOR MODE

(WIGGLE TEST)

The continuous Monitor Modes allow the technician to ATTEMPT to recreate an intermittent fault.

The needle of the VOM will sweep across the face of the meter when a fault is recreated.

KEY ON ENGINE OFF

1.

Hook up a VOM as shown in Quick

Test.

2.

DO NOT ground STI if using a VOM or "Check Engine" Light.

3.

Turn the ignition key to the ON position.

4.

You are now in the Continuous

Monitor Mode.

5.

Tap, Move and Wiggle the suspect sensor and/or harness. If a fault is detected, a Service Code will be stored in memory and will be indicated as explained previously.

ENGINE RUNNING

1.

Hook up VOM as shown in Quick

Test Step.

2.

Start the engine.

3.

Activate Self-Test, wait 10 seconds, deactivate and reactivate Self-Test.

DO NOT shut the engine off.

4.

You are now in the Engine Running

Continuous Monitor Mode.

5.

Tap, move, and wiggle thesuspect sensor and/or harness. If a fault is detected, a Service Code will be stored in memory and will be indicated as explained previously.

CYLINDER BALANCE TEST

The Cylinder Balance test on the

5.0L SEFI and 5.0L SEFI MA vehicles is designed to aid in the detection of a noncontributing cylinder.

The Cylinder Balance test, first reads engine rpm, with all injectors activated.

Next, each injector is turned "off and on," one at a time. The rpm drop that results, if any, is then read. These two rpm's are compared to verify that the rpm drop was greater than a calibrated level.

The Cylinder Balance Test service codes correspond with cylinder number followed by a "O" on a scanner. Example

20 = cyl #2.

1.

Perform Engine Running Self-Test.

2.

After the last repeated service code is received, wait 5-10 seconds.

3.

Lightly depress and release throttle

(not wide-open throttle) within two mintutes of the last repeated service code.

4.

Cylinder Balance Test will be per formed at the first test level.Test

time is approximately three minutes.

5.

Within 2 minutes after the previous

Cylinder Balance Test, lightly de press and release the throttle to enter 2nd/3rd level Cylinder Balance

Test.

6.

If a throttle is touched (moved) during Cylinder Balance Test,

Service Code 77 will appear, indicating test was not completed.

The 2nd/3rd level Cylinder Balance Test is intended to aid in the detection of any partially contributing injectors.

OUTPUT STATE CHECK

This mode is entered after all codes have been received from Key On Engine

Off and Continuous Testing. At this time, leave Self-Test activated and depress the throttle. Each time the throttle is depressed, the output actuators will change state from energized to de-energized or from de-energized to energized.

1.

Enter Self-Test.

2.

Code Output Ends.

3.

Do Brief WOT.

4.

EEC-IV Output To Actuators

TOMCO TECH TIP #6

Energized.

5.

Do Brief WOT.

6.

EEC-IV Output To Actuators De-

Energized.

HOW TO CLEAR

CONTINUOUS MEMORY

CODES

1.

Run the Key On Engine Off Self-

Test according to Quick Test.

2.

When the Service Codes begin to

be displayed, deactivate Self-Test:

Disconnect the jumper wire from the Self-Test connector.

3.

The continuous service codes will be erased from the processor's memory.

EEC CODES 1984 TO

1988 (Difference in

Years noted)

O = KOEO test key on engine off

R = KOER test key on engine

running

M = in memory - after separator

(10) in KOEO test

Code

11 system OK

Definition

12 (R) Idle Speed Control (ISC) motor or Air Bypass not controlling idle properly (generally idle too slow)

13 (O) ISC did not respond properly

Electronic Control Assembly

(Processor)(ECA ext/retracts for test)

(R) RPM’s out of specs

(usually too high)

(M) Idle Speed Control ISC

(motor) sticking, open Idle

Tracking Switch ITS circuit or

Throttle Pos. Sensor TPS sticking

14 (M) Profile Ignition Pickup PIP was erratic (poss secondary ignition arcing, wiring problem or 2-way radio interference?)

15 (O) No keep Alive Memory power

(pin 1) or bad Electronic

Control Assembly (Processor)

ECA

(M) Keep Alive Memory (KAM) (pin

1) was interrupted (poss batt.

was disconnected)

16 (R) Erratic idle during test or throttle was touched (try resetting throttle stop)

17 (R) Same as 16

18 (R) Check base timing, advance function or ignition ground

(M) Ignition Tachometer (TACH sig.) was erratic (poss wiring,

Outside Frequency Interfer-

TOMCO TECH TIP #6 ence (IFI prob)

19 (O) No Voltage Power (pins 37 +

57) or bad Electronic Control

Assembly (Processor) ECA

(R) Low idle Revolutions Per

21

22

Minute (RPM)

Engine Coolant Temp.

(ECT)(run for 2 minutes and retest)

Manifold Absolute Pressure

23

24

(MAP) sensor out of range

Throttle Position Sensor (TPS) out of range or throttle set too high

Air Charge Temp Sensor

(ACT)out of range (84-86 with

Vane meter) Vane Air Temperature (VAT) sensor out of range

25 (R) Knock sensor not tested

26

(ignore if not pinging)

Vane Air Flow sensor out of range

27 (M) Vehicle Speed Sensor problem

(see 29)

28

29

Vane Air Temp sensor out of range

Vehicle Speed Sensor (VSS) problem (clear memory and test drive to confirm)

31(OR) EGR Valve Position or Pressure Feedback EGR Transducer (PFE) sensor out of range

(M) Intermittent EGR Valve

Position (EVP) or Pressure

Feedback (EGR) Transducer

(PFE) signal (poss open or short to gnd.)

32 (O) EGR Valve Position (EVP) sensor signal too low or EGR valve problem

(R.M) Pressure Feedback EGR or

(EVP) lower than normal

33 (R) EGR did not respond during test

(M) EGR Valve Position (EVP) was out of range

34 (O) MPFE: Low exh.press., blocked sensor tube or bad sensor

EGR Valve Position (EVP): If

CODE 84 PRESENT GOTO 84

(R) Cars with EGR cont/ vent solenoids: EGR not controlling Cars with EVR: EVP or FFE signal too high Cars with EGR cutoff solenoid: Remove shop exhaust hose and rerun test or perform output state check

(M) PFE equipped: check for blockage in PFE sensor tube

EVP equipped: check EVP resistance while moving valve

35 (O) PFE or EVP too high or

shorted to power

(R) Cars with EGR solenoids:

RPM’s too low to test EGR All others: Excess exhaust pressure (restricted?) blocked PFE tube or bad EVP, PFE sensor

(M) Intermittent EVP or PFE signal

(poss open signal return or short to power)

38 (M) Idle Tracking Switch (ITS) signal was intermittent

39 (M) Intermittent in Lock-Up Solenoid (LUS) circuit

41 (R) System running lean (3.8L left if dual)(5.0L right)

(M) System was lean for 15 seconds or more

42 (R) System running rich (3.8L left

if dual)(5.0L right)

(M) System was rich for 15 seconds or more

43 (R) Oxygen Sensor(EGO) not reading (Run engine at 2000 rpm’s for 2 minutes and retest)/ check EGO voltage

(M) System was lean at Wide

Open Thrott. for 3 sec. or more

44 (R) Thermactor air system not working

45 (R) Thermactor air not Diverting

Thermactor Air Diverter (TAD)

46 (R) Thermactor air Bypass not working Thermactor Air By-

Pass (TAB)

47 (R) Unmetered air getting around

Air Flow box (low flow)

48 (R) Unmetered air getting around

Air Flow box (high flow)

51 (O.M) Coolant sensor (ECT) signal too high or open circuit

52 Power Steering Press Switch/ circuit open

(R) Steering wheel not turned during test or PSPS problem

53 (O.M) Throttle Pos sensor too high

(to power or stuck open)

54 (O.M) Air Charge Temp sensor input high or open circuit

(O.M) (84-86 with Vane meter)

Vane Air Temperature (VAT)

55 out of range/ open circuit

No Key Power (pin 5) to processor or charging system problem (undercharging or overcharging)

56 (O.M) Vane Air Flow sensor input too high (poss to power)

(R) Mass Air Flow sensor high or

57 shorted to power

Intermittent in Neutral/ Drive

Switch (NDS) circuit

58 (0.R) Idle Tracking Switch signal

too high - switch or circuit open

(opens when touching throttle)

(O.M) (87.88 with Vane meter)

(VAT) out of range/ open circuit

59 (O.M) Automatic Overdrive Transmission (AXOD) 4/3 circuit

fault (poss short to ground)

61 (O.M) Coolant (ECT) sensor too low or signal line grounded

62 (O) Automatic Overdrive Transmission (AXOD) 3/2 circuit short to ground

(R) Automatic Overdrive Transmission (AXOD) 4/3 circuit failure

63 (O.M) Throttle Position Sensor

(TPS) sensor signal too low

(grounded or open circuit)

64 (O.M) Air Charge Temperature

Sensor (ACT) signal too low or signal line grounded

(O.M)(84-86 with Vane meter) Vane

Air Temperature (VAT) out of range or grounded

65 (84 3.8L) (O.M) Battery volt too high (check for o’ charging)

(88)(M) Check intermittent

Heated Exhaust Gas Oxygen

Sensor (HEGO) orob (signal or ground)

66 (O.M) Vane Air Flow (VAF) signal low (poss short to ground or open)

(R) Mass Air Flow (MAF) sensor low (disconnected or grounded)

67 (O.R) MAKE SURE A/C IS OFF! -

Neutral Drive Switch (NDS) circuit fault or WOT A/C

Throttle (WAC) circuit

(O) (4.8L truck hold clutch in while running test)

(M) Intermittent Neutral Drive

Switch (NDS) fault

68 (O.R) ITS closed or grounded

(O.M)(87.88 with Vane meter)

(VAT) out of range or grounded

69 (O.M) Transmission Hydraulic

Switch-3rd/2nd Gear THS-3/2 circuit short to ground

71 (M) Intermittent Idle Tracking

Switch (ITS) (if equipped) or intermittent Vehicle Supply

Voltage, Power (VPWR) Circuit

(pins 37 + 57) (poss power relay problem) or Electronic

Control Assembly (Processor)

(ECA) case ground (pin 20 to case and/ case to chassis should be 5 ohms or less)

72 (R) No Manifold Absolute Pressure

(MAP) change in “goose” test

(M) See 71

73 (R) Throttle Position Sensor (TPS) did not change in “goose” test

(must get 25%)

(O) Rerun test, if 73 is still output replace Throttle Position

Sensor (TPS)

74 (R) Brake-on-off Switch (B00) Did

TOMCO TECH TIP #6 not step on brk during test or

800 short to gnd

75 (R) (B00) signal shorted to power

(brake light switch stuck on?)

76 (R) Vane Air Flow (VAF) did not respond to “goose” test

77 (R) System did not receive “goose” test or throttle was touched during balance test

78 (M) See 71

79

81

A/C is on or A/C clutch wire is shorted to power 89 series:

CIRCUIT OR SOLENOID

PROBLEMS

Boost control solenoid or Ther-

82

83 mactor Air By-Pass (TAB)/

Thermactor Air Diverter (TAD) solenoid

Electro-Drive Fan EDF signal wire shorted to ground or Thermactor Air By-Pass (TAB)/

Thermactor Air Diverter (TAD) solenoid

High Speed Electro-Drive Fan

HEDF circuit fault or Exhaust

Gas Recirculation EGR solenoid

84(O.R) Solenoid/ circuit fault for Electronic Vacuum (or Voltage)

Regulator (EVR) Exhaust Gas

Recirculation (EGR) cutoff solenoid or Exhaust Gas Recirculation (EGR) solenoids, which ever is present

85 (O.R) Shift solenoid 3/4-4/3 or circuit fault Canister Purge

(CANP) solenoid or circuit if equipped

(M) System has corrected a rich condition

86 (M) System has corrected a lean condition

87 (O) Fuel pump relay/ circuit fault

(check inertia switch)

(M) Intermittent in fuel pump circuit

(Escort with automatic seat

88

89 belts normal IN MEMORY due to wiring)

Throttle Kicker Solenoid. Variable Voltage Choke (VVC) relay. Electro Drive Fan circuit fault or Converter Clutch

Override (CCO) solenoid, whichever is present

Converter Clutch Override

(CCO) solenoid Lock Up Sole

90 noid (LUS) or Exhaust Heat

Cross-over (EHC) solenoid, whichever is present

System pass during balance test 91, 92, 93, 94 fuel codes: see also 41, 42, 43, 44

91 (R.M) System running lean (3.8L

right if dual)(5.0L left)

92 (R) System running rich

93 (O) Throttle linkage binding or bad

Idle Speed Control (ISC)

(motor)

(R) Oxygen sensor Exhaust Gas

Oxygen Sensor(EGO) not reading (3.8L R. 5.0L L.)(See

43)

94 (R) Thermactor air not working

95 (O) Fuel pump: open circuit, bad ground or always on

(R) Thermactor air not Diverting

(M) Poss. bad fuel pump ground or open circuit between fuel pump circuit and pin 8 at Electronic

Control Assembly (Processor)

(ECA) (Fuel Pump Monitor signal)

96 (O) Fuel pump not getting power when activated

(R) Thermactor air Bypass not working (3.8L R. 5.0L L.)

(M) Service 27 code first if present)

Fuel pump relay or battery power feed was open (wiggle power connections while running and check for stall)

98 (R) Vehicle did not pass Key On

Engine Off (KOEO) test (Get !!

in KOEO first)

99 (R) Idle Speed Control (ISC) needs to lean (idle 2 minutes, erase mem and retest)

CHECKING CANISTER

PURGE VALVES

These valves, used on late carburetor equipped GM vehicles, vent fuel vapors from the carburetor bowl to the charcoal canister. They also control the purging of the bowl vapors from the canister along with any fuel vapors accumulated in the canister from the fuel tank.

When the valve is operating properly vapors are permitted to enter the intake manifold only when certain engine speeds and temperature conditions are attained.

When purge valve failure occurs fuel mixtures become very rich, stumble on acceleration, poor fuel mileage and flooded charcoal canister and overheating of the exhaust catalytic converter can occur.

Two types of external canister purge valves have been used by GM.

Single Diaphragm Type

Valve

When the engine is not running, spring tension holds the valve open.

This allows venting of the float bowl.

When the engine is running, manifold vacuum pulls the plunger up to close the valve. see fig.#4

MANIFOLD

DIAPHRAGM

ASSEMBLY

VACUUM

SPRING

CARBURETOR

BOWL

Fig 4

Fig 5

PURGE

VACUUM

CANISTER

VALVE

SEAT

Double Diaphragm Type

Valve

When the engine is running, manifold vacuum from the positive crankcase ventilation (PCV) System pulls the lower diaphragm upward to shut off venting of the float bowl.

When the engine is running above idle speed, control vacuum pulls the upper diaphragm upward to allow purging of the canister through the PCV System.

see fig #5

OFF THE CAR TESTS

Use a hand operated vacuum pump such as shown IN FIG. 6. A short rubber hose helps in blowing through the connection with lung pressure to check if the valve operates properly.

Fig 6

TOMCO TECH TIP #6

TESTING THE SINGLE

DIAPHRAGM TYPE

VALVE

.

APPLY 15" VAC

SHOULD HOLD

20 SEC

Fig 7

TESTING THE DOUBLE DIAPHRAGM TYPE

VALVE

APPLY 15" VAC

SHOULD HOLD

20 SEC

Fig 9

APPLY 15" VAC

SHOULD HOLD

20 SEC

BLOW

IN HERE

NO AIR

HERE

AIR SHOULD COME

OUT HERE

NO AIR HERE

BLOW

IN HERE

NO AIR HERE

Fig 10

Fig 11

NO AIR HERE

Fig 8

BLOW

IN HERE

AIR SHOULD COME

OUT HERE

AIR SHOULD COME

OUT HERE

AIR SHOULD COME

OUT HERE

Fuel in the valve or hoses may come from condensation of fuel vapors and is not always an indication of a defective valve. Most problems have been due to ruptured diaphragms.

Any vacuum leak, pinched or kinked hose or intake manifold leak will upset the system. Either the

ECM or Oxygen sensor, or both, will receive an incorrect signal causing their output to also be in error.

The end result could be driveability complaints and higher than normal exhaust emissions.

A complete check of connecting hoses - PCV valves charcoal canister and its filter should be made when servicing the canister purge valve.

NEW PLATINUM II O

2

SENSOR

The oxygen or O 2 sensor is a very critical sensing device in the automotive computer circuit. It functions as an electrical generator using exhaust heat and the presence or absence of oxygen to create a low voltage signal to the computer. As it senses oxygen in the exhaust system, it sends a voltage signal of 200 millivolts to 1 volt to the computer - indicating that the exhaust mixture is rich or lean. The sensors ability to switch quickly from a low to a high voltage is an important operating function.

Tomco's Platinum II Sensor has been designed to have the fast switching characteristics needed to operate todays high speed computer systems. The new Platinum II sensors compact design eases installation on those hard to get at locations.

TOMCO TECH TIP #6

EXHAUST AIR LEAKS BADLY AFFECT OXYGEN SENSOR OUTPUT

Recently we encountered a problem of an O2 sensor that always indicated a low voltage

(Lean fuel mixture) when checked with a voltmeter. A slight exhaust leakage sound could be heard. The area around the manifold was covered by a sheet metal heat shield. A hairline crack in the manifold became visible when the shield was removed.

Most mechanics think of the exhaust system as having only positive pressure.

With the valve overlap present in modern engines a low pressure pulse exists in the exhaust manifold that can draw in oxygen and cause the O 2 sensor to deliver a lean (low voltage) signal to the computer.

Replacment of the exhaust manifold fixed the problem.

(A.I.R.)INJECTION

TUBES

A.I.R. Injection Tubes distribute air from the air pump to the exhaust system to help reduce harmful emissions. Because of the corrosive effect of exhaust gases, they rust through causing an exhaust leak.

Inspect for rust and exhaust leakage with engine running.

With engine off, grasp the tubes and check to see if they are still tight and in good condition.

A.I.R. Injection Tubes often develop leaks and thin sections due to the corrosive effect of gases and may break off when moved during other engine service. They are in the same system as

A.I.R. Pump Check Valves and should be checked when an A.I.R. Pump Check

Valve is replaced.

TOMCO TECH TIP #6

THIS BIRD WAS JAILED ON 2 COUNTS

FUEL INJECTION

MANUAL T1-90

It always seems easier to diagnose and fix a mechanical problem if one understands how the device or engine system operates. Tomco's

Electronic Fuel Injection Manual is designed to promote a better understanding of these computer controlled fuel systems. Our recent updated issue now contains over 900 pages cover the diagnosis and testing of domestic and import cars, light trucks and vans through the very latest models. Each fuel injection system is covered by a theory of operation section, a trouble-shooting guide, pressure, voltage and resistance specifications and complete fuel system wiring diagrams. This manual has been used as a text in fuel injection clinics held across the country. The T1-90 replaces the earlier T1-89 issue.

Contact TOMCO for ordering information.

#1. Stole Gas

#2. Polluted Our Air

A BAD Oxygen Sensor

STEALS GAS And POLLUTES

PROBLEM:

• It Works In The RED HOT Corrosive Exhaust.

• Leaded Fuel, Anti-Freeze, Excessive Oil

Burning and Silicone Sprays Poison It.

A Sluggish Or Dead Oxygen Sensor...

• Wastes As Much As 3 Out of Every 10 Gallons

Of Gas.

• Pollutes The Air.

• Ruins Catalytic Converters.

SOLUTION: Replace Oxygen

Every 25,000 Miles With....

TOMCO'S NEW PLATINUM II SENSOR

PAT.PEND.

Here's Why...

• Two Platinum Layers For

Longer Life.

• Quicker Warm-Up Saves

Gas.

• Faster Action Saves Gas.

• Reduces Pollution

• Engineered For All

Domestic And Import Cars.