Tune-Up - v8 Pontiac Firebird III

VEHICLE IDENTIFICATION NUMBER CODE

Engine can be identified by the eighth character of Vehicle Identification Number (VIN). The VIN is located on top left corner of instrument panel, and is visible through windshield.

VIN ENGINE CODES

TUNE-UP NOTES

Note. When performing tune-up procedures described in this article, the following notes and precautions must be followed

Due to late changes, always refer to Engine Tune-Up Decal in engine compartment before performing tune-up. If manual and decal differ, use decal specifications.

With the exception of initial ignition timing, normal tune-up procedures are not required. Adjust fuel system only when indicated by the computer Command Control (CCC) System Performance Check or poor engine performance.

Damage to the HEI electronic module and/or coil may result if "TACH" terminal is grounded. Do not remove spark plug wires with engine running. This would cause an overly rich mixture which may damage catalytic converter.

Before making compression test, or cranking engine with a remote starter switch, disconnect the "BATT" terminal connector from distributor.

ENGINE COMPRESSION

During compression test, engine must be at normal operating temperature, all spark plugs removed and throttle (and choke) valve must be in WOT position. See COMPRESSION SPECIFICATIONS table. Crank engine through 4 or more compression strokes.

COMPRESSION SPECIFICATIONS

SPARK PLUGS

SPARK PLUG TYPE

SPARK PLUG INSTALLATION

HIGH TENSION WIRE RESISTANCE

Carefully remove wire end and boot from spark plug and distributor. Using an ohmmeter, check resistance while gently twisting wire. If resistance is incorrect, or if resistance fluctuates, wire must be replaced.

WIRE RESISTANCE (OHMS)

FUEL PUMP

Perform all tests at idle RPM. Pinch off fuel return line (if equipped). Connect pressure gauge to fuel line at carburetor or throttle body and hold gauge level with carburetor or throttle body.

FUEL PUMP PERFORMANCE

Distributor

All models use a Delco-Remy High Energy Ignition with Electronic Spark Timing (HEI-EST).

PICK-UP COIL RESISTANCE (OHMS)

Ignition Coil Resistance (Ohms)

1. Connect ohmmeter between ignition coil primary and coil frame. Reading should be infinite on high scale of meter. Disconnect ohmmeter from coil frame and connect it to the other coil primary terminal. Reading should be very low or zero on low scale of meter.
2. Disconnect ohmmeter lead from one of the coil primary terminals and connect it to coil secondary terminal. Reading should not be infinite on high scale of meter.

VALVE CLEARANCE

VALVE CLEARANCE ADJUSTMENT

4.1L (VIN 7 & 8) & 5.0L (VIN Y & 9)

Both Banks - I-E-I-E-E-I-E-I (Front-to-rear).

All Other Engines

Both Banks - E-I-I-E-E-I-I-E (Front-to-rear).

All models are equipped with High Energy Ignition (HEI) systems with Electronic Spark Timing (EST). No adjustments are required.

4.1L (VIN 7 & 8) Firing Order & Timing Marks. Scheme 1

5.0L (VIN Y & 9) Firing Order & Timing Marks. Scheme 2

5.0L (H, G & F) & 5.7L Firing Order & Timing Marks. Scheme 3

IGNITION TIMING

Note. Some engines are equipped with a socket for a magnetic probe timing meter, located 9.5° ATDC. Do not use this location for timing with a conventional timing light.

4.1L (VIN 7 & 8)

1. Place transmission in Park. Warm engine to normal operating temperature. Turn off all accessories. Remove air cleaner. Plug any open vacuum lines. Start engine.
2. Install jumper wire between terminals "A" and "B" of ALDL connector. Verify that the "SET TIMING" message is displayed, or "ENGINE SOON" light is flashing.
3. Set timing at any speed less than 800 RPM. Remove jumper wire from ALDL. Tighten the distributor hold-down bolt (or nut) and re-check timing.

5.0L (VIN F) & 5.7L (VIN 8)

1. Engine must be at normal operating temperature. Turn A/C and all accessories off. Verify that "CHECK ENGINE" light is off.
2. Put EST into by-pass mode by unplugging "Set Timing" timing connector. Connector is a Tan/Black wire in the wiring harness near the distributor. DO NOT unplug 4-wire connector at distributor.
3. Connect timing light to No. 1 spark plug. Set timing at specified idle speed. Tighten distributor housing and recheck timing. Connect all wiring and vacuum hoses. Reconnect "Set Timing" connector. Clear ECM trouble code by momentarily disconnecting ECM power source.

5.0L (VIN G) & 5.7L (VIN 6)

1. Engine must be at normal operating temperature with choke fully open. Air cleaner must be installed. Turn A/C and all accessories off.
2. Unplug 4-wire connector at distributor. Set ignition timing at specified idle speed. Plug in 4-wire connector. Clear ECM trouble code by momentarily disconnecting ECM power source.

5.0L (VIN H, Y & 9)

1. Engine must be at normal operating temperature with choke fully open. Turn A/C and all accessories off. Connect tachometer to engine. Connect timing light to No. 1 spark plug.
2. With engine running, install a jumper wire between terminals "A" and "B" of diagnostic connector. Connector is under left side of instrument panel near steering column.
3. Set timing at specified engine RPM. See IGNITION TIMING SPECIFICATIONS table below. Recheck timing after tightening distributor housing. With engine still running, remove jumper wire from diagnostic connector (if removed before engine is shut off, no trouble code will be stored).

IGNITION TIMING SPECIFICATIONS

HOT (SLOW) IDLE RPM - CARBURETED

Note. On most models, idle speed is controlled by ECM and Idle Speed Control (ISC) motor. Other models use standard solenoids or vacuum-operated Idle Load Compensator (ILC). Identify system used on vehicle, then follow adjustment procedures.

Idle Speed (With Solenoid)

1. Warm engine to normal operating temperature and adjust timing. Air cleaner must be installed. Choke must be fully open.
2. Disconnect wire from idle solenoid. Adjust idle speed screw to correct curb idle speed. Connect lead to solenoid. Disconnect compressor clutch wire and turn A/C on (if equipped).
3. Unplug electrical lead from solenoid and connect a 12-volt supply. Open throttle to extend solenoid plunger. Turn solenoid plunger to set correct solenoid RPM. Connect compressor clutch wire and solenoid wire. Turn A/C off (if equipped).

IDLE SPEED (RPM)

Idle Speed (With Idle Load Compensator)

1. Place transmission in "P", set parking brake, and block wheels. Remove air cleaner and plug hose to Thermal Vacuum Valve (TVV). Disconnect and plug hoses to EGR, canister purge port, and idle load compensator (ILC). Engine must be at normal operating temperature.
2. Back out throttle stop screw 3 turns. With engine running and transmission selector in "D", adjust plunger to set "plunger extended" RPM. Hold jam nut on plunger to avoid damaging ILC.
3. Measure distance from jam nut to tip of plunger. (Scheme 4) Dimension must not exceed 1" (25.4 mm). If dimension exceeds 1" (25.4 mm), check for a low idle condition.
4. Reconnect engine vacuum to ILC and observe idle speed. Idle speed should match "plunger retracted" RPM. If correct, go to step 9). If idle is not correct, stop engine.

Note. It is not necessary to remove ILC if Allen wrench is modified to clear obstructions.

Scheme 4

IDLE LOAD COMPENSATOR ADJUSTMENT (RPM)

Scheme 5

1. Prior to adjustment, check for identification letter on adjustment plunger. If no letter appears, remove plunger from ISC motor and measure length of plunger. (Scheme 5)
2. Record measurement. Adjust plunger in motor so that distance "B" is less than distance "A." (Scheme 5) If letter appears, record letter.
3. Place transmission in "P", set parking brake, and block drive wheels. Remove and plug vacuum hoses at air cleaner. Remove air cleaner. Connect dwell meter to carburetor mixture control (M/C) solenoid lead (Green). Set meter on 6-cylinder scale (regardless of engine size). NOTE: Do not unplug or connect ISC connector with ignition on.
4. Turn A/C and all accessories off. Start engine and warm to normal operating temperature. Engine must be operating in "closed loop" (dwell meter needle varying).
5. Connect tachometer to engine. Turn ignition off. Unplug electrical connector from ISC motor. Retract plunger by applying 12 volts to ISC motor terminal "C" and ground terminal "D". NOTE: DO NOT leave battery voltage applied to ISC motor. Remove voltage as soon as plunger is retracted (extended). Never connect battery voltage across terminals "A" and "B".
6. Start engine and wait until dwell meter begins to vary indicating "closed loop." With parking brake applied, shift transmission into "D." With plunger fully retracted, adjust stop screw to set Minimum Authority RPM. See IDLE SPEED CONTROL (ISC) ADJUSTMENTS table.
7. Place transmission in "P." Extend plunger by applying 12 volts to terminal "D" and ground terminal "C." Leave power applied only long enough to extend plunger. When plunger is extended, it must be in contact with throttle lever to prevent damage to unit.
8. Place transmission in "D." With plunger fully extended, check Maximum Authority RPM. Turn ISC plunger with Adjuster (J-29607) to specified RPM. Recheck Maximum Authority RPM with voltage applied to ISC motor. Readjust if necessary. MINIMUM & MAXIMUM AUTHORITY RPM Application Minimum Maximum 5.0L (VIN Y) 450 (1) 700 (1) Set with transmission in Drive.
9. After adjustment, measure distance from back side of plunger head to ISC nose piece (distance "B"). Dimension must not exceed that specified by plunger identification letter or distance "A."

IDLE SPEED CONTROL (ISC) ADJUSTMENTS

HOT (SLOW) IDLE RPM - FUEL INJECTED ENGINES

Note. On 4.1L DFI engine, idle speed is controlled by ECM. Idle adjustment is necessary only when ISC or throttle body has been replaced. Prior to adjusting idle speed, record, diagnose, repair, and clear all trouble codes in ECM memory.

4.1L DFI & MFI

1. Remove air cleaner and warm engine to normal operating temperature. Turn A/C and all accessories off. Check and adjust engine timing. Cooling fan must not be running during adjustments.
2. Place steering wheel in center position and transmission selector in "P." Retract ISC motor.
3. To retract ISC, unlock ISC motor connector but do not disconnect motor. Open throttle and hold it at approximately 1500 RPM. With same hand, close throttle switch by depressing ISC plunger. When fully retracted, continue to hold throttle open and throttle switch closed while disconnecting ISC motor. Return throttle to idle. NOTE: Do not power ISC motor in fully retracted position for more than 4 seconds or ECM damage may occur.
4. On MFI engines, retract the ISC motor by selecting ECM override ES03 "ISC Motor." Press the "COOLER" button on the CCDIC. The ISC will slowly retract to a fully retracted position (about 20 seconds). Once the ISC has fully retracted, make sure that the throttle lever is resting on the minimum idle speed screw.
5. ISC plunger should now be retracted. If plunger still contacts throttle lever, turn plunger in so it is not touching. With idle speed control (ISC) plunger fully retracted and not touching throttle lever, check minimum idle speed RPM. MINIMUM IDLE SPEED RPM Application Idle Speed 4.1L (VIN 7 & 8) 475-550
6. Check TPS adjustment. See THROTTLE POSITION SENSOR (TPS) ADJUSTMENT. With ISC motor fully retracted and throttle against stop screw, turn ISC motor plunger adjustment screw to obtain a .160" (4.06 mm) gap between throttle lever and plunger. Disconnect all test equipment and plug in all harness connectors. Turn off ignition for at least 10 seconds. Start engine. Check ISC motor for proper operation.
7. This procedure might have recorded intermittent trouble codes in DFI computer. After all connections have been made and system is restored to normal operation, codes must be cleared.

Note. On 5.0L and 5.7L TPI engines, idle speed is controlled by ECM and will normally vary. Idle speed adjustment is not normally required. The following adjustment is for minimum idle speed only.

Scheme 6

1. Pierce idle stop screw plug with an awl and remove it. (Scheme 6) With Idle Air Control (IAC) motor connected, ground diagnostic lead. Ground lead by installing jumper wire between terminals "A" and "B" in diagnostic connector. Connector is located under left side of instrument panel near steering column.
2. Turn ignition on, but do not start engine. Wait 30 seconds. With ignition on, disconnect IAC connector. (Scheme 6): 5.0L & 5.7L TPI Idle Screw Plug Removal
3. Remove ground from diagnostic lead and start engine. Allow engine to go into "closed loop" mode. Adjust idle screw to specifications. See IDLE SPEED RPM table. Turn ignition off and connect IAC motor. Adjust TPS. See THROTTLE POSITION SENSOR (TPS) ADJUSTMENT. Start engine and check for proper idle operation.

IDLE SPEED RPM

THROTTLE POSITION SENSOR (TPS) ADJUSTMENT - CARBURETED

Note. TPS adjustment screw is factory-sealed. No adjustment should be performed unless indicated by CCC System Performance Check.

Note. Before proceeding with TPS voltage check and adjustment, ensure that idle RPM is set to specification on vehicle emission control information label.

5.0L & 5.7L 4-Bbl.

1. Without separating connector, connect a high impedance digital voltmeter from TPS connector center terminal "B" to bottom terminal "C." Turn ignition switch to "ON" position with engine off.
2. Disconnect idle solenoid connector and ensure that throttle lever is against idle speed screw. Voltage reading should be .50-.58 volts on models with E4ME carburetor, or should not to exceed .7 volts on models with E4MC carburetor. If voltage is incorrect, adjust TPS voltage by removing plug covering TPS adjustment screw.
3. Using a 5/64" drill bit, drill a hole 1/16-1/8" (1.6-3.2 mm) deep in plug covering TPS adjustment screw. Do not damage screw head. Start a 1/2" long No. 8 screw in drilled hole, seating only enough for good thread engagement. Using a screwdriver, pry against screw to remove plug. Discard plug.
4. Using TPS Wrench (J-28696 or BT-7967-A), adjust TPS screw to obtain .50-.58 volts. Install new plug to seal setting after adjustment. Clear ECM memory if diagnostic code was set during adjustment.

Scheme 7

4.1L DFI

1. Ignition must be on with engine stopped. Use a high impedance digital voltmeter to measure voltages. With throttle closed against stop screw, measure and record reference voltage at TPS terminals "B" (Gray) and "C" (Black/White).
2. Connect positive lead of voltmeter to TPS harness test point at terminal "A" (Dark Blue). Connect negative lead to terminal "B." Set voltmeter on 2-volt DC scale. Measure and record TPS voltage between terminals "A" and "B."
3. Determine correct TPS voltage from reference voltage recorded. See 4.1L TPS ADJUSTMENT VOLTAGE chart. To adjust TPS voltage, loosen attaching screws and rotate TPS. Recheck TPS voltage after tightening attaching screws.

4.1L MFI

1. With the engine running, select ECM override ES03 "ISC Motor" and press the cooler button (retract ISC motor). Select ECM data ED01 "TPS" while still in the ECM override ES03. If the throttle position displayed on the ECM data ED01 is: +0.8 to +2.0, go to next step.
2. Measure the TPS signal voltage by connecting a high impedance digital voltmeter to the TPS test point. With the meter set to the two volt scale, connect the meter positive lead to CKT 417, Dark Blue wire, and the negative lead to CKT 476, Black/White wire.
3. With engine still running, loosen the TPS screws just enough to permit the sensor to be rotated. A T-25 torx driver should be used for TPS adjustment. Adjust the TPS so that the voltmeter reads 0.475-0.525 volts. Tighten the TPS mounting screws with the sensor in the adjusted position. Recheck ECM data ED01 to be sure that the TPS angle is + 0.8 to +2.0-.

4.1L TPS ADJUSTMENT VOLTAGE

5.0L & 5.7 TPI

1. Install 3 jumper wires between TPS and harness connector or use an ALCL display tool. With ignition on and engine stopped, connect a digital voltmeter to terminals "A" and "B." Loosen TPS adjusting screws to obtain .54 volts.
2. Tighten screws to 18 INCH lbs. (2 N.m). Recheck reading to ensure adjustment has not changed. With ignition off, remove jumper wires and connect harness to TPS.

IDLE MIXTURE ADJUSTMENT

Note. Idle mixture adjustment is not required on fuel injected models. On carbureted models, mixture should be adjusted only if vehicle fails emission testing or carburetor has been disassembled.

Mixture Screw Plug Removal - Carbureted Models

1. Remove carburetor from engine and drain fuel into container. Place carburetor in a holding fixture with manifold side up.
2. Use hacksaw to make 2 small parallel cuts on throttle body, one on each side of locator points beneath idle mixture plugs. Cuts should extend down to steel plug, but not extend more than 1/8" (3.2 mm) below locator points.
3. Using a flat punch or chisel, break out throttle body between saw cuts to gain access to plugs. Use punch to drive out plug. If hardened plug shatters, remove loose pieces. Repeat procedure to remove remaining plug. Install carburetor on engine.

Idle Mixture Adjustment - Carbureted Models

1. Using Remover/Installer (J-29030-B or BT-7610-B), remove both idle mixture screws and springs. Inspect needles for damage and needle openings for damage or foreign material.
2. Reinstall mixture screws and springs in throttle body. Using remover/installer, turn both mixture screws clockwise until lightly seated. Turn each mixture screw counterclockwise 3 turns.
3. Reinstall carburetor on engine using a new flange gasket. Proceed to IDLE MIXTURE CONTROL ADJUSTMENT step 9) to finalize correct dwell reading.

Scheme 8

1. Mixture control solenoid must be checked before adjustment. Stop engine. Remove air cleaner and gasket. Insert Float Gauge (J-34935 or BT-8420-A) in "D" shaped hole in air horn (next to idle air bleed valve cover). Gauge checks float level externally. It may be necessary to grind material off gauge to allow it to enter hole.
2. With gauge installed, read and record gauge mark that lines up with top of air horn. Lightly press down to bottom gauge. Total travel should be 1/16-3/16" (1.6-4.8 mm). If travel is correct, go to step 3). If solenoid plunger travel is not correct, carburetor must be disassembled and readjusted.
3. Set parking brake and block drive wheels. Disconnect and plug canister purge hose. Connect tachometer to engine. Check ignition timing and adjust, if necessary.
4. Connect a dwell meter to Green wire from mixture control solenoid in carburetor. Set dwell meter on 6-cylinder scale. Warm engine to normal operating temperature. A varying dwell should be noted on dwell meter. NOTE: Engine must be run long enough to ensure engine coolant sensor and oxygen sensor are at full operational temperature.
5. Adjust curb idle speed (on models with ISC or ILC, do not adjust). With engine idling in Drive (Neutral on man. trans.), observe dwell reading. If dwell needle is moving within 10-50°, no adjustment is necessary. If needle is fixed at one point or outside this range, see SYSTEM PERFORMANCE CHART in the appropriate TESTS W/CODES article in the ENGINE PERFORMANCE section. Return to next step if flow charts indicate carburetor adjustments, calibration or service are necessary.
6. Stop engine. Cover carburetor air intakes and vents with tape. Drill rivet heads on idle air bleed plug (above primary bores). Remove plug and blow out metal chips and rivet pieces.
7. Install Gauge (J 33815 2 or BT 8253 B) in "D" shaped hole on throttle side of air horn. Position gauge so upper end is over open cavity next to idle air bleed valve. (Scheme 8)
8. Lightly hold gauge down to seat solenoid plunger against its stop. Adjust idle air bleed valve so that gauge will pivot over and just touch top of valve. Remove gauge.
9. Start engine and allow it to reach normal operating temperature. Ensure canister purge hose is disconnected and plugged. While idling in Drive (Neutral on man. trans.), adjust idle air bleed valve with screwdriver until dwell varies within 25-35° range. Try to get as close to 30° as possible. NOTE: Perform this step carefully. Idle air bleed valve is very sensitive in controlling air/fuel ratios. Valve should be turned only in 1/8 turn increments.
10. If dwell reading does not vary and is not within 25-35° range after this adjustment, it will be necessary to remove plugs covering idle mixture screws. After removing plugs, adjust idle mixture as follows
11. Turn mixture screws in until lightly seated. Back each screw out 3 turns. Install carburetor with new flange gasket. Repeat step 9).
12. If unable to set dwell to 25-35°, and dwell is below 25°, turn both mixture screws out one turn. If above 35°, turn both mixture screws in one turn.
13. Readjust idle air bleed valve to obtain dwell limits. Seal idle mixture screws with silicone sealant or RTV. Mixture control adjustment is complete if dwell at 3000 RPM varies between 10-50° and there is at least a 300 RPM drop from full rich to full lean.
14. Idle mixture adjustment is complete if closed loop dwell at idle varies between 10-50° and there is no rough engine idle.

Carbureted Engines

1. Engine must be at normal operating temperature with choke fully open. Air cleaner must be installed and A/C off.
2. Disconnect and plug vacuum hoses at EGR valve. Position cam follower on high step of fast idle cam. On 5.0L (VIN Y or 9), place cam follower on low step of fast idle cam.
3. On 5.0L (VIN Y or 9), apply vacuum to ILC with vacuum pump to retract ILC plunger. On all models, turn fast idle screw to set correct fast idle RPM. Adjust fast idle speed within 15 seconds after idle speed reaches 700 RPM.

FAST IDLE SPEED SPECIFICATIONS

Digital Fuel Injection

Fast idle on 4.1L engines is controlled by the Electronic Control Module through the Idle Speed Control (ISC) motor. Fast idle adjustment is not possible.

Tuned-Port Fuel Injection

Fast idle on 5.0L and 5.7L TPI engines is controlled by the Electronic Control Module through the Idle Air Control (IAC) assembly. Fast idle adjustment is not possible.

Multi-Port Fuel Injection

Fast idle on 4.1L engines is controlled by the Electronic Control Module through the Idle Air Control (ISC) motor. Fast idle adjustment is not possible.

AUTOMATIC CHOKE

All carbureted models are equipped with a riveted, indexed choke cover. Choke is not adjustable.

ALTERNATOR REGULATOR

All models except 27SI use a Delco-Remy nonadjustable regulator, integral with alternator. The 27SI uses a Delco-Remy adjustable regulator, integral with alternator.

REGULATOR OPERATING VOLTAGE

FUEL SYSTEM

CARBURETORS

FUEL INJECTION

ALTERNATOR

All models use a Delco-Remy SI alternator with integral regulator.

ALTERNATOR SPECIFICATIONS

BATTERY

BATTERY SPECIFICATIONS

STARTER

All models are equipped with a Delco-Remy solenoid actuated starter with overrunning clutch.

STARTER SPECIFICATIONS

SERVICE INTERVALS

REPLACEMENT INTERVALS

BELT ADJUSTMENT

BELT ADJUSTMENT (1)

CAPACITIES

COOLING SYSTEM CAPACITIES

ENGINE OIL & FUEL CAPACITIES

TRANSMISSION & DIFFERENTIAL CAPACITIES

SYSTEM REFRIGERANT CAPACITIES