Tune-Up - v8 Chevrolet Forward Control P30

ENGINE IDENTIFICATION

Engines can be identified by 8th character of Vehicle Identification Number (VIN). Number is located on plate at top left corner of dashboard and at base of steering column on Van models.

Engine code numbers are located at front of block, at right cylinder head on 5.0L and 5.7L engines and in front of intake manifold on 7.4L engines.

VIN ENGINE CODES

TUNE-UP NOTES

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

1. Due to changes and corrections, always refer to Engine Tune-Up Decal in engine compartment before attempting tune-up. In the event of a conflict between specifications given in this manual and decal specifications, decal specifications prevail.
2. For tune-up purposes, "Light Duty" refers to vehicles up to 8500 lbs. "Heavy Duty" refers to vehicles exceeding 8500 lbs.
3. When performing tune-up on vehicles equipped with a catalytic converter, do not allow or create a condition of engine misfire in one or more cylinders for an extended period of time. Damage to converter from overheating may occur due to loading with unburned fuel.

ENGINE COMPRESSION

When making compression checks, disconnect ignition switch connector Pink wire from high energy ignition system. With air cleaner removed and throttle and choke wide open, crank engine through at least 4 compression strokes.

COMPRESSION SPECIFICATIONS

SPARK PLUGS

SPARK PLUG TYPE

SPARK PLUG SPECIFICATIONS

HIGH TENSION WIRE RESISTANCE

Carefully remove ends of wire from spark plug and distributor. Using an ohmmeter, check resistance while gently twisting wire. If resistance is not to specifications, or fluctuates from infinity to any value, replace cable.

HIGH TENSION WIRE RESISTANCE (OHMS)

5.0L & 5.7L

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

7.4L

1. Left Bank - E-I-E-I-E-I-E-I (Front-to-rear).
2. Right Bank - I-E-I-E-I-E-I-E (Front-to-rear).

VALVE CLEARANCE

All vehicles are equipped with hydraulic lifters. Lifters should be adjusted to one turn down from zero lash.

DISTRIBUTOR

California 5.0L and 5.7L engines are equipped Delco-Remy High Energy Ignition with Electronic Spark Timing (HEI-EST).

Federal 5.0L high compression (9.2:1) engines use Electronic Spark Control (ESC) ignition system with detonation sensor.

All other engines are equipped with High Energy Ignition (HEI) systems and no adjustments are required.

Firing Order & Timing Mark (Magnetic Timing Pick-Up Is Located At 10 Degrees ATDC). Scheme 4

IGNITION TIMING

Note. Engines are equipped with a receptacle for magnetic probe timing lights, located 10° ATDC. Do not use this location for timing with a conventional light.

1. Connect an adapter between No. 1 spark plug wire or use an inductive type pick-up. Do not puncture wires. Connect timing light according to manufacturer's instructions.
2. Check or adjust ignition timing with engine at normal operating temperature, distributor vacuum line (if equipped) disconnected and plugged. Light duty models with automatic transmission should be in Drive; all others in Neutral.
3. On California Models with HEI-EST and HEI-ESC distributors, disconnect 4-wire plug connector at distributor when checking ignition timing. Once timing has been set, reconnect connector and clear trouble code from computer.

IGNITION TIMING SPECIFICATIONS (DEGREES BTDC @ RPM)

Curb Idle and Throttle Return Control (TRC)

1. Set ignition timing to specifications. Disconnect lead from idle solenoid (if equipped). Adjust curb idle speed to specifications using idle speed screw. Transmission should be in Drive for light duty models with automatic transmission, and in Neutral on all others.
2. Disconnect lead from A/C compressor. Reconnect lead at idle solenoid. Turn A/C on. Open throttle slightly to allow solenoid to fully extend. Adjust solenoid idle speed by turning solenoid screw.
3. On heavy duty engines equipped with TRC, connect a hand vacuum pump to control diaphragm. With engine idling, apply sufficient vacuum to extend plunger fully.
4. Open throttle slightly to allow plunger to fully extend. Screw plunger in or out as necessary to obtain specified RPM.

IDLE SPEED (RPM)

THROTTLE RETURN CONTROL (RPM)

Scheme 5

Scheme 6

1. Check identification letter on ISC plunger. (Scheme 5) If no letter appears, remove plunger from unit using Wrench (J-29607 or BT-8022).
2. Measure and record length of plunger from back side of plunger head to end of screw. This is dimension "A". (Scheme 5) Install plunger so that distance measured from back side of plunger to ISC nose piece is less than dimension "B".
3. Remove air cleaner, disconnect and plug EGR and canister purge hoses. Connect tachometer to engine. Connect dwell meter (set on 6-cylinder scale) to mixture control solenoid dwell lead. Turn A/C off. Start engine and run until meter starts to vary. (Scheme 5): Idle Speed Control (ISC) Adjustment NOTE: Do not disconnect or connect ISC connector with ignition on as damage to ECM may occur.
4. Turn ignition off and unplug connector from ISC motor. Retract plunger by applying 12V to terminal "C" of ISC motor connection and ground lead to terminal "D" of ISC motor connection. (Scheme 6)
5. Start engine and wait until dwell meter begins to vary. Set parking brake, block drive wheels and place transmission in "D" (auto. trans.) or Neutral (man. trans.). With plunger fully retracted, adjust idle stop screw to curb idle specification. (Scheme 6): ISC Motor Connections
6. Place transmission in "P" (auto. trans.). Fully extend plunger by applying 12V to terminal "D" and ground terminal "C". Leave power applied only long enough to extend plunger.
7. Using Adjuster (J-29607 or BT-8022), adjust solenoid idle speed on vehicles with manual transmissions. Preset plunger to 1500 RPM on vehicles with automatic transmissions. Place transmission in "D", then adjust solenoid idle speed using adjuster. IDLE SPEED (RPM) Application Curb Idle Solenoid Idle Speed Calif. Light Duty (5.0L & 5.7L) 550 650
8. Recheck solenoid idle speed with voltage applied to motor. After adjustment of plunger, measure distance from back side of plunger to ISC nose piece. Dimension "B" must not exceed specification shown.
9. Fully retract plunger and turn ignition off. Disconnect battery leads, tachometer and dwell meter. Connect 4-terminal connector.

IDLE SPEED CONTROL PLUNGER SPECIFICATIONS

Idle Load Compensator (ILC) (M4MC Carburetor Only)

1. Place transmission in "P", set brakes and block drive wheels. Connect tachometer to engine. 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).
2. Back out idle stop screw 3 turns. Turn A/C off. With engine running and transmission selector in "D", check that ILC plunger is fully extended. Adjust plunger to obtain 725 RPM. Hold jam nut on plunger to avoid damage to ILC.
3. Remove plug from vacuum hose, reconnect hose to ILC. Idle speed should be 500 RPM in "D". If speed is correct, no further adjustment is necessary. If speed is not correct, proceed to next step.
4. Stop engine and remove ILC. Plug vacuum hose to ILC. With ILC removed, remove rubber cap or metal plug from center outlet tube.
5. Install ILC and related parts on carburetor. Remove plug from vacuum hose and reconnect to ILC. Using a spare rubber cap with a hole punched to accept a 3/32" Allen wrench, install cap on center outlet tube.
6. Start engine and turn adjusting screw to obtain 500 RPM in "D". Remove wrench and cap. Install new rubber cap.
7. With engine running and transmission in "D", measure distance from jam nut to tip of plunger. This distance must not exceed 1" (25.4 mm). (Scheme 7)
8. Disconnect and plug vacuum hose to ILC. Apply vacuum to ILC inlet tube to fully retract plunger. Adjust idle stop screw on carburetor float bowl to obtain 500 RPM in "D". Stop engine, reconnect all hoses and remove test equipment.

Adjusting Idle Load Compensator. Scheme 7

Throttle Position Sensor (TPS)

1. Adjust TPS only if it is not adjusted correctly, or if it is necessary to replace air horn assembly, float bowl, TPS sensor or TPS adjustment screw.
2. Using a 5/64" drill bit, drill a 1/16" to 1/8" deep hole in aluminum plug covering TPS adjustment screw. Use care not to damage screw head. (Scheme 8)
3. Start a No. 8-1/2" long self-tapping screw in drilled hole, turning screw in only far enough to ensure good thread engagement. Using a screwdriver between screw head and air horn, pry out plug.
4. Using TPS Adjuster (J-28696), remove TPS adjusting screw. Connect digital voltmeter from TPS connector center terminal "C" to bottom terminal "C".
5. With ignition on, engine stopped, install TPS adjustment screw to obtain specified TPS voltage with A/C off.
6. Install new plug in air horn. If new plug not available, use Delco Threadlock Adhesive X-10 on TPS adjustment screw. Adjust voltage, as in step 5).

TPS Adjustment Screw Location For E4ME (Plug Must Be Drilled Out To Adjust Screw). Scheme 8

TPS VOLTAGE ADJUSTMENT

Mixture Screw Plug Removal

1. Remove carburetor from engine and drain fuel. Invert carburetor. Make 2 parallel cuts in throttle body, one cut on each side of locator points beneath idle mixture needle plug.
2. The cuts should reach down to steel plug, but should not extend more than 1/8" beyond locator points. The distance between saw marks depends on size of punch to be used.
3. Place a flat punch at a point near ends of saw marks in throttle body. Holding punch at a 45° angle, drive it into throttle body until casting breaks away, exposing steel plug.
4. Holding a center punch vertically, drive it into steel plug. Holding punch at a 45° angle, drive out steel plug.

Propane Enrichment Procedure Federal Light Duty Models Only

1. With engine at normal operating temperature, choke fully open and A/C off (if equipped), set parking brake and block drive wheels.
2. Connect tachometer to engine. Disconnect vacuum advance and set timing to specification. Reconnect vacuum advance. Disconnect crankcase ventilation tube from air cleaner.
3. Insert hose with rubber stopper from propane valve into PCV tube opening in air cleaner. Propane bottle must be in vertical position.
4. Slowly open control valve until maximum engine speed is reached with transmission in "D" (auto. trans.) or Neutral (man. trans.).
5. Observe propane flow meter to ensure propane cartridge is full. With propane flowing, observe idle speed. Continue to add propane until speed drops off. Note maximum idle speed.
6. If idle speed is within specification, mixture is correct. No further adjustments are necessary. If not correct, proceed with adjustment procedure.
7. Lightly seat idle mixture adjustment screws. Back out equally, just enough so engine will run. Place transmission in "D" (auto. trans.) or Neutral (man. trans.).
8. Turn each mixture screw out 1/8 turn at a time until maximum idle speed is reached. Set idle speed to enriched idle speed specification. Turn each idle mixture screw in 1/8 turn at a time until idle speed matches specification. See IDLE SPEED (RPM) table.
9. Re-check enrichment speed with propane. After adjustments are complete, seal idle mixture adjustment screws with RTV.
10. Turn off propane, unplug and reconnect all vacuum hoses. Install air cleaner. Recheck idle speed and repeat procedure if necessary.

PROPANE ENRICHED RPM (FEDERAL LIGHT DUTY)

Heavy Duty Models Only

1. Set parking brake and block drive wheels. Warm engine to normal operating temperature. Remove air cleaner. Place transmission in Neutral and connect tachometer.
2. Turn idle mixture screws in lightly to seat them, then back out 2 turns. Do not turn screws tightly against seat or damage may result.
3. With engine running, choke open, and transmission in Neutral, adjust idle speed to specification. Adjust mixture screws to obtain maximum RPM.
4. Readjust idle speed screw to specification, and readjust mixture screws to obtain highest RPM. Turn ignition off, and install air cleaner.

Mixture Control Solenoid Plunger Travel

1. Idle mixture control solenoid plunger travel should be checked before mixture adjustment or disassembly. Use Float Gauge (J-9789-130 or BT-7720) to check float level externally.
2. Insert gauge in "D" shaped vent hole in air horn casting, next to Idle Air Bleed cover. It may be necessary to file material off gauge to allow it to enter vent hole.
3. Turn engine off. Remove air cleaner and gasket. Check that gauge moves freely in vent hole. With gauge released, record reading of gauge mark that lines up with top of air horn casting.
4. Lightly press down on gauge and record reading of gauge mark that lines up with top of air horn casting. Total plunger travel must be between 1/8" (3.2 mm) and 3/8" (9.5 mm).
5. If plunger travel is within specifications, proceed to Idle Air Bleed Valve Adjustment. If plunger travel is incorrect, carburetor must be disassembled and adjusted.

Scheme 9

Scheme 10

1. Mixture must not be adjusted unless carburetor has been disassembled for cleaning or parts replacement or a systems performance check indicates that carburetor is cause of malfunction.
2. If adjustment is necessary, check ignition timing. Connect tachometer to engine. Connect dwell meter to Green wire of mixture control solenoid on carburetor.
3. Set dwell meter to 6-cylinder scale. Bring engine to operating temperature and check idle speed. Adjust idle and curb idle speed if necessary. On models with ILC or ISC, curb idle is controlled by ECM.
4. With engine idling in "D" (auto. trans.) or Neutral (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 if it is outside this range, see SYSTEM PERFORMANCE CHART in COMPUTER CONTROLS article in COMPUTER CONTROLS section. Return to next step if flow charts indicate carburetor adjustments, calibration or service are necessary.
5. Turn engine off. Cover internal bowl vents, air inlets to bleed valve and carburetor air inlets with masking tape to prevent metal chips from entering carburetor.
6. Use a No. 35 (.110") drill bit to drill out rivet heads on either side of idle air bleed valve cover. Lift off idle air bleed valve cover and remove rivet pieces from carburetor. On models without rivets, pry cover off.
7. Look for letter identification code on top of idle air bleed valve. Not all valves will have an identification code. NOTE: On idle air bleed valves WITHOUT a letter code, the following procedure (setting valve to gauge dimension) is not necessary unless the idle air bleed valve was serviced prior to on-vehicle adjustment.
8. To set idle air bleed valve to gauge dimension, install Air Bleed Valve Gauge (J-33815-2 or BT-8253-B) in throttle side "D" shaped hole in air horn casting. (Scheme 10) (Scheme 9): Idle Air Bleed Valve Identification (Check For Letter Identification Code On Top Of Valve) (Scheme 10): Positioning Idle Air Bleed Valve (Hold Gauging Tool Down Lightly)
9. Upper end of gauge should be positioned over open cavity, next to air bleed valve. Hold gauge down lightly against solenoid stop.
10. Adjust idle air bleed valve so that gauge will pivot over and just contact top of valve. Valve is now ready for adjustment. NOTE: If idle air bleed valve HAS a letter code, air bleed valve does NOT have an adjustment. Proceed to Adjusting Idle Mixture Needles.
11. Start engine and bring to operating temperature. While idling in "D" (auto. trans.) or Neutral (man. trans.), use a screwdriver to adjust valve until a dwell reading of 25-35° is obtained.
12. If dwell reading is not within 25-35°, remove mixture needle plugs and adjust idle mixture needles.

Adjusting Idle Mixture Needles

1. Turn each needle clockwise until lightly seated. Back out needles 3 turns. Bring engine to operating temperature.
2. For valves WITH letter code, adjust both needles equally, in or out, until dwell meter reads as close to 30° as possible. After adjustment is complete, seal mixture needle openings with RTV sealant.
3. For valves WITHOUT letter code, readjust air bleed valve. If unable to set dwell to 25-35° range, turn mixture needles equally in or out to bring dwell reading within range. Readjust idle air bleed valve, and seal mixture needle openings with RTV sealant.

AUTOMATIC CHOKE

The choke cover on all engines is riveted in place, and no adjustments are possible or necessary.

COLD (FAST) IDLE RPM

1. Place transmission in "P" (auto. trans.) or Neutral (man. trans.). Place cam follower on highest step of fast idle cam. On light duty vehicles; disconnect and plug vacuum hose to EGR valve, canister purge hose and purge signal hose at canister.
2. Start engine without touching throttle. Turn fast idle speed screw to adjust speed to specification.

FAST IDLE SPEED (RPM)

California 5.0L and 5.7L engines are equipped with Delco-Remy High Energy Ignition with Electronic Spark Timing (HEI-EST).

Federal 5.0L high compression (9.2:1) engines use Electronic Spark Control (ESC) ignition system with detonation sensor.

All other models are equipped with High Energy Ignition (HEI) systems and no adjustments are required.

Note. High energy ignition system module must be replaced as a unit. A liberal coat of silicone grease MUST be applied to both module and its mounting surface.

DISTRIBUTOR PICK-UP COIL RESISTANCE

BATTERY

BATTERY SPECIFICATIONS @ 0°F (-18°C)

STARTER

All models are equipped with Delco-Remy overrunning clutch starters.

STARTER SPECIFICATIONS

IGNITION COIL

IGNITION COIL RESISTANCE - OHMS @ 75°F (24°C)

COIL OUTPUT

FUEL PUMP

FUEL PUMP SPECIFICATIONS

FUEL SYSTEMS

CARBURETORS

ALTERNATOR

All models are equipped with Delco-Remy alternators with integral voltage regulators. No adjustments are possible.

ALTERNATOR SPECIFICATIONS @ 80°F (27°C)

ALTERNATOR REGULATOR

Regulators are Delco nonadjustable, integral with alternator.

REGULATOR SPECIFICATIONS

SERVICE INTERVALS

REPLACEMENT INTERVALS

BELT ADJUSTMENT

BELT ADJUSTMENT (TENSION IN LBS. (KG) USING STRAND TENSION GAUGE)

CAPACITIES

FLUID CAPACITIES

SYSTEM REFRIGERANT CAPACITY