Tune-Up - 5.7l v8 VIN [l] GMC Vandura I

ENGINE IDENTIFICATION

Engines can be identified by eighth digit 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.

VIN ENGINE CODES

TUNE-UP NOTES

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

The 5.7L (VIN L) has two different emission packages available; California and Federal. The fundamental difference is the California package has a feedback engine management system (E4ME carb./HEI-EST), whereas the Federal package is not using a feedback system (M4ME carb./HEI-ESC). Be careful to note when a procedure or specification only applies to one of the specific emission packages.

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.

For tune-up purposes, "Light Duty" refers to vehicles up to 8500 lbs. "Heavy Duty" refers to vehicles exceeding 8500 lbs.

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 the 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 four compression strokes.

COMPRESSION SPECIFICATIONS

VALVE CLEARANCE

All vehicles are equipped with hydraulic lifters. Lifters should be adjusted to 1 turn down from zero lash.

VALVE ARRANGEMENT

E-I-I-E-E-I-I-E (Both banks, front-to-rear)

FIRING ORDER & DISTRIBUTOR/PICKUP INFORMATION

The California emissions 5.7L engine is equipped with the Electronic Spark Timing (HEI-EST) ignition system. The Federal emissions 5.7L is a high compression (9.2:1) model and uses an Electronic Spark Control (ESC) ignition system with detonation sensor.

Timing Mark & Firing Order: Timing Socket at 10 Degrees ATDC. Scheme 9

DISTRIBUTOR PICKUP COIL RESISTANCE

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.

Federal Emissions Models

1. Connect an adapter between No. 1 spark plug wire or use an inductive type pickup. 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 disconnected and plugged. (Scheme 9) Models with automatic transmission should be in "D", all others in neutral.

California Emissions Models

1. Connect an adapter between No. 1 spark plug wire or use an inductive type pickup. DO NOT puncture wires. Connect timing light according to manufacturer's instructions.
2. Check or adjust ignition timing with engine at normal operating temperature. (Scheme 9) The transmission should be in "D", and the 4-wire connector should be disconnected at the distributor.
3. After the check/adjustment is completed, reconnect the 4-wire distributor connector. Note that a false trouble code will be stored in the ECM's memory because of the disconnected the 4-wire plug. Clear the code if necessary.

TIMING SPECIFICATIONS

SPARK PLUG SPECIFICATIONS

SPARK PLUG SPECIFICATIONS

SPARK PLUG TYPE

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.

RESISTANCE

IGNITION COIL SPECIFICATIONS

COIL RESISTANCE

COIL OUTPUT

CARBURETOR USAGE

CARBURETOR

FUEL PUMP SPECIFICATIONS

FUEL PUMP SPECIFICATIONS

MIXTURE SCREW PLUG REMOVAL

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

MIXTURE CONTROL SOLENOID PLUNGER TRAVEL CHECK

1. Idle mixture control solenoid plunger travel should be checked before any mixture adjustments or disassembly. Use float gauge J-9789-130 or BT-7720 to check float level externally.
2. Insert gauge in the vertical "D" shaped vent hole in the air horn casting, next to the Idle Air Bleed cover. It may be neces- sary to file material off the gauge to allow it to enter the vent hole.
3. Engine must be off and air cleaner and gasket removed. Check that gauge moves freely in vent hole. With gauge released, record the reading of the gauge mark that lines up with the top of air horn casting.
4. Lightly press down on gauge and record reading of gauge mark that lines up with the top of air horn casting. Total plunger travel must be between 1/16" (1.6 mm) and 3/16 (4.8 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. See appropriate article in FUEL SYSTEMS section.

IDLE AIR BLEED VALVE ADJUSTMENT

1. Mixture must not be adjusted unless carburetor has been disassembled for cleaning or parts replacement or "Systems Performance Check" indicates the carburetor is the cause of any malfunction.
2. If adjustment is necessary, check ignition timing accord- ing to directions on Emission Control Label under hood. Connect a 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. Curb idle is controlled by the ECM via ISC and is not subject to routine adjustments. However, if idle is incorrect, an Idle Speed Solenoid or Idle Load Compensator (used on some models to position the primary throttle valve) could be failing. Check them for proper operation.
4. With engine idling in "DRIVE", 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 appropriate article in the ENGINE PERFORMANCE 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 the bleed valve and carburetor air inlets with masking tape to prevent metal chips from entering carburetor.
6. Use a No. 35 (.110") drill to drill out the rivet heads on either side of the idle air bleed valve cover. Life off idle air bleed valve cover and remove any rivet pieces from carburetor.
7. Look for a letter identification code on top of the idle air bleed valve. (Scheme 10) Not all valves will have an identification code. NOTE: On idle air bleed valves WITHOUT a letter code: steps 8 through 10 (setting valve to gauge dimension) are not necessary unless the idle air bleed valve was serviced prior to on-vehicle adjustment.
8. To set idle air bleed valve to a gauge dimension, install air bleed valve gauging tool (J-33815-2 or BT-8253-B) in throttle side "D" shaped hole in the air horn casting. (Scheme 11)
9. The upper end of the tool should be positioned over the open cavity next to the air bleed valve. Hold the gauging tool down lightly against the solenoid stop.
10. Adjust the idle air bleed valve so that the gauging tool will pivot over and just contact the top of the valve. The valve is now ready for adjustment. NOTE: If the idle air bleed valve HAS a letter code, the air bleed valve does NOT have an adjustment. Skip steps 11 & 12, and proceed to "Adjusting Idle Mixture Needles".
11. Start engine and bring to operating temperature. While idle in "DRIVE", use a screw- driver to adjust valve until a dwell reading of 25-35° is obtained.
12. If dwell reading is NOT within the 25-35° range, remove the mixture needle plugs and adjust the mixture needles.

IDLE MIXTURE NEEDLES ADJUSTMENT

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 air bleed valve and seal mixture needle openings with RTV sealant.

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. Scheme 11

AUTOMATIC CHOKE

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

CARBURETOR

FUEL PUMP SPECIFICATIONS

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

IDLE MIXTURE CHECK & ADJUST (PROPANE ENRICHMENT)

1. With engine at normal operating temperature, choke fully open and A/C "OFF" (if equipped), set parking brake and block drive wheels. Disconnect and plug hoses as directed on Emission Control/ Tune-Up decal.
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 (tool J-26911) 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" (automatic) or neutral (manual). NOTE: Too much propane will cause engine speed to drop.
5. Observe propane flow meter to ensure propane cartridge is full. With propane flowing, adjust idle speed screw or solenoid so speed rises above normal idle by specified amount.
6. Readjust propane flow to be certain of maximum engine speed and adjust idle speed if necessary. Turn off propane. Run engine at 2000 RPM in neutral for 30 seconds, return to idle, and place in "D".
7. Check idle speed. If correct, no adjustment of mixture is necessary. If not correct, proceed with adjustment procedure. If idle speed is too low, carefully remove caps from mixture screws and back out screws (richen) 1/8 turn at a time until correct speed is reached.
8. If RPM is too high, turn screws in (leaner) 1/8 turn at a time until correct speed is reached. Turn propane on again to check maximum engine idle speed.
9. If RPM does not meet specifications, readjust idle speed screw or solenoid screw to obtain specified enriched RPM with propane flowing.
10. Turn off propane, place transmission in neutral and run engine at 3000 RPM for 30 seconds. Recheck idle speed and repeat procedure if necessary.

PROPANE ENRICHED RPM

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

COLD (FAST) IDLE RPM

1. Place transmission in neutral. Move cam follower onto highest step of fast idle cam. 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.

Note. For information regarding the choke, look at AUTOMATIC CHOKE under FUEL SYSTEMS in this article.

FAST IDLE SPEED

DESCRIPTION/APPLICATION

An Idle Speed Control (ISC) assembly, monitored by the ECM, controls engine idle speed. The curb (or base) idle speed is programmed into the ECM and IS NOT ADJUSTABLE. However, if the ISC has been replaced or tampered with, it can cause idle speed problems. See the following procedure to set/verify proper ISC adjustment.

Also, an Idle Speed Solenoid (ISS) or Idle Load Compensator (ILC) is used on some models to position the primary throttle valve, providing the proper engine idle. To adjust them, see the following procedures (as applicable).

IDLE SPEED CONTROL (ISC) MOTOR ADJUSTMENT

1. Prior to adjustment, check for an identification letter on the ISC plunger. If no letter appears, remove plunger from unit.
2. Measure length of plunger from back side of plunger head to end of plunger screw. This is dimension "A". (Scheme 12)
3. Install plunger so that the distance measured from the back side of the plunger to ISC nosepiece is LESS than dimension "B". See ISC Plunger Identification table. Follow Vehicle Emission Information Label to prepare vehicle for adjustments. WARNING: DO NOT disconnect or connect ISC connector with ignition "ON" as damage to the ECM may occur.
4. Connect tachometer to engine. Connect dwell meter to mixture control solenoid dwell lead. Set dwell meter to 6-cylinder scale regardless of engine being tested. Turn A/C off. Start engine and run until dwell meter starts to vary.
5. Turn ignition off and unplug connector from ISC motor. Retract ISC plunger by applying 12V to terminal "C" of ISC motor connection and ground lead to terminal "D" of the ISC motor connection. (Scheme 13)
6. Start engine and wait until dwell meter needle begins to vary. Block wheels and place transmission in "D". With ISC plunger fully retracted, adjust carburetor IDLE STOP screw to curb idle specification.
7. Place automatic transmission in "P". Fully extend plunger by applying 12V to terminal "D" and ground lead to terminal "C". Leave power applied only long enough to extend plunger.
8. Preset the plunger to 1500 RPM. Set parking brake and block drive wheels. Set idle speed to specifications.
9. Recheck idle speed with voltage applied to motor. After adjustment of ISC plunger, measure distance from back side of plunger to ISC nosepiece (dimension "B" in Fig. (Scheme 12) ).
10. Dimension must not exceed specification. Plunger type is identified by plunger length or letter identification. Refer to the «IDLE SPEED CONTROL PLUNGER IDENTIFICATION»(/gmc/vandura/i-1970-1996/remont/adjustments/#tune-up-57l-v8-vin-l) table.
11. Fully retract ISC plunger and turn ignition off. Disconnect battery leads, tachometer and dwell meter. Reconnect 4-terminal harness connector.
12. The procedure described above will cause code to be stored as an "Intermittent" problem. It will be necessary to clear the diagnostic trouble codes. See appropriate article in this section.

Adjusting Idle Speed Control Unit After plunger adjustment, dimension "B" must not exceed specification. Scheme 12

ISC Motor Connections NEVER connect voltage across terminals "A" & "B". Scheme 13

IDLE SPEED CONTROL PLUNGER IDENTIFICATION

IDLE SPEED CONTROL SOLENOID (ISS)

Note. Not all models are equipped with an ISS.

1. Prepare vehicle for adjustments according to directions on Emission Label on vehicle. Disconnect solenoid and turn air conditioning off. Set curb idle speed with idle speed screw.
2. Connect solenoid. Disconnect A/C lead at compressor and turn A/C ON. Place transmission in "D".
3. Open throttle to extend solenoid plunger. Turn solenoid screw to adjust RPM. Reconnect A/C lead.

IDLE LOAD COMPENSATOR (ILC)

Note. Not all models are equipped with an ILC.

1. With transmission in "P", brakes set and wheels blocked, prepare vehicle for adjustments. 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. Verify A/C is "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 damaging 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 the ILC. Plug vacuum hose to ILC. With the ILC hose removed, remove the rubber cap from the center outlet tube. Remove the metal plug (if used) from this same tube.
5. Install ILC and all related parts on carburetor. Remove plug from vacuum hose and reconnect hose to ILC. Using a spare rubber cap with a hole punched to accept a.090" (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 and install new rubber cap. With engine running and transmission in "D", measure distance from the jam nut to the tip of plunger.
7. This distance must not exceed 1" (25 mm). (Scheme 14)
8. Disconnect and plug vacuum hose to ILC. Apply vacuum source to ILC inlet tube to fully retract plunger. Adjust idle stop screw on carburetor float bowl to obtain 500 RPM in "D".
9. Stop engine. Reconnect all hoses and remove test equipment.

Adjusting Idle Load Compensator Measure with engine running and transmission in "DRIVE". Scheme 14

IDLE SPEED

HOT (SLOW) IDLE RPM - FEDERAL EMISSIONS ONLY

Note. See engine compartment Emission Control Tune-Up Decal to prepare engine for idle speed adjustment.

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 "D" for automatic transmission, and in neutral on all others.
2. Disconnect lead from air conditioning compressor. Reconnect lead at idle solenoid, then turn air conditioning "ON". Open throttle slightly to allow solenoid to fully extend. Adjust solenoid idle speed by turning solenoid screw.

Note. Not all models are equipped with an ILC

1. With transmission in "P", brakes set and wheels blocked, prepare vehicle for adjustments. 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 damaging 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 the ILC. Plug vacuum hose to ILC. With the ILC hose removed, remove the rubber cap from the center outlet tube. Remove the metal plug (if used) from this same tube.
5. Install ILC and all related parts on carburetor. Remove plug from vacuum hose and reconnect hose to ILC. Using a spare rubber cap with a hole punched to accept a.090" (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 and install new rubber cap. With engine running and transmission in "D", measure distance from the jam nut to the tip of plunger.
7. This distance must not exceed 1" (25 mm). (Scheme 14)
8. Disconnect and plug vacuum hose to ILC. Apply vacuum source to ILC inlet tube to fully retract plunger. Adjust idle stop screw on carburetor float bowl to obtain 500 RPM in "D".
9. Stop engine. Reconnect all hoses and remove test equipment.

A/C IDLE SPEED CONTROL SOLENOID (ISS)

Note. Not all models are equipped with an ISS

1. Prepare vehicle for adjustments according to directions on Emission Label on vehicle. Disconnect solenoid and turn air conditioning off. Set curb idle speed with idle speed screw.
2. Connect solenoid. Disconnect A/C lead at compressor and turn A/C on. Place automatic transmission in "D" and manual transmission in neutral.
3. Open throttle to extend solenoid plunger. Turn solenoid screw to adjust RPM. Reconnect A/C lead.

THROTTLE POSITION SENSOR (TPS) ADJUSTMENT

Note. This procedure only applies to California emissions vehicles.

1. DO NOT readjust the TPS unless the TPS is not adjusted correctly or it is necessary to replace the air horn assembly, float bowl, TPS sensor or TPS adjustment screw.
2. Using a 5/64" (2 mm) drill, drill a 1/16" to 1/8" deep hole in aluminum plug covering TPS adjustment screw. Use care not to damage screw head. (Scheme 15)
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 screw driver between screw head and air horn, pry out plug.
4. Using tool (J-28696), remove TPS adjustment screw. Connect digital voltmeter from TPS connector center terminal (B) to bottom terminal (C).
5. With ignition on, engine stopped, install TPS adjustment screw to obtain specified TPS voltage with A/C off. Refer to the «TPS VOLTAGE ADJUSTMENT»(/gmc/vandura/i-1970-1996/remont/adjustments/#tune-up-57l-v8-vin-l) table.
6. Install new plug in air horn. If new plug not available, use Delco Threadlock Adhesive X-10 on screw threads then adjust voltage.

TPS Adjustment Screw Location for E4ME Plug must be drilled out to adjust screw. Scheme 15

TPS VOLTAGE ADJUSTMENT

EMISSION CONTROL

No emission control information is contained in this article. Instead, please see the appropriate EMISSIONS article.

ALTERNATOR SPECIFICATIONS

All models are equipped with Delco alternators with integral voltage regulators.

ALTERNATOR SPECIFICATIONS

ALTERNATOR REGULATOR SPECIFICATIONS

Regulators are Delco nonadjustable, integral with alternator.

REGULATOR SPECIFICATIONS

BATTERY SPECIFICATIONS

BATTERY

STARTER SPECIFICATIONS

All models are equipped with Delco overrunning clutch starters.

STARTER SPECIFICATIONS

BASIC SERVICE INTERVALS

REPLACEMENT INTERVALS

FLUID CAPACITIES

FLUID CAPACITIES

BELT ADJUSTMENT SPECIFICATIONS

BELT ADJUSTMENT (1)

See also:
• FUEL SYSTEMS