CPI ENGINE NOISE-INSTALL NEW GEARS/ENGINE EXCH./NEW MEMCAL. GMC Truck S15 Pickup - 4WD 1992

For 1990-2009 cars

# CPI ENGINE NOISE-INSTALL NEW GEARS/ENGINE EXCH./NEW MEMCAL

#### SUBJECT: CPI ENGINE NOISE (INSTALL NEW GEARS/NEW MEMCAL)

VEHICLES AFFECTED: 1992 "S,T,M,L" TRUCKS WITH 4.3L ENGINE (RPO L35)

ENGINE (VIN) W

THIS BULLETIN SUPERSEDES AND REPLACES CORPORATE BULLETIN REFERENCE NUMBER 23611**. THIS BULLETIN IS BEING REVISED TO GMSPO PART NUMBERS AND CHANGES TO THE WARRANTY INFORMATION.

The 1992 model year 4.3L (L35) Engine Exchange Program is discontinued effective the end of December, 1992.

#### CONDITION:

Some 1992 4.3L CPI engines may exhibit one or both of the following noises:

1. A tick or rattle noise at idle or low engine speeds up to 1300 RPM. The noise may occur hot or cold in Park/Neutral or in gear.

2. A detonation or rattling type noise under acceleration at engine speeds between 2000 - 2500 RPM. It is usually most noticeable at the shift points under moderate acceleration with the transmission torque converter unlocked. Premium grade fuel does not affect the noise.

3. If an engine has both noises (conditions "l " and "2", follow condition "2" for cause and correction instructions and information.

#### CAUSE:

1. The most probable cause for the idle tick or rattle (condition #1) is due to zero or near zero lash between the balance shaft drive gears. Some gears may feel as if the lash is acceptable but there is most likely an area on one of the teeth which is not meshing properly with the other gear.

2. The source of the detonation or rattling type noise under acceleration between 2000 - 2500 rpm (condition #2) is the rear balance shaft needle bearing. With some engines, the rear needle bearing is excited by a combination of factors (i.e., engine case, combustion events, balance shaft gear lash, valve train torque reversals, cam chain play, needle bearing clearance, etc.).

#### IMPORTANT: If there is any question about the proper diagnosis of the noise, call Technical Assistance. The unnecessary customer inconvenience and/or replacement of parts must be avoided. It is important to note that neither noise is a reliability or dependability concern. The noises are a customer pleasability issue only. The life of the engine will not be shortened due to the above causes.

#### CORRECTION:

1. The following steps should be followed to correct an idle tick noise (condition #1).

a. Remove the accessory drive belt.

b. Start the engine and note the noise. If it is still present proceed to step 'c'; if not, proceed with diagnosis of accessory drive per the service manual procedures.

#### NOTE: Do not allow the engine to operate for an extended period of time with the accessory drive belt off. Remember the water pump and fan are not functioning. Overheat will eventually occur.

C. Contact Technical Assistance. Arrangements will be made to deliver a set of matched balance shaft drive gears . Replace the balance shaft drive gears with the ones supplied.

Steps to replace balance shaft gears:

A. Disconnect battery. B. Drain coolant. C. Remove fan shroud. D. Remove accessory drive belt. E. Remove fan. F. Remove the water pump. G. Remove crankshaft pulley and harmonic balancer. H. Remove transmission torque converter cover. Let it lie on top of exhaust crossover pipe. I. Drop the oil pan by leaving the rear two nuts on the crankshaft seal studs about 1/4 inch from tight. The two studs will stabilize the oil pan and the oil will not have to be drained. J. Remove the front cover. K. It is recommended that the engine be turned over by hand so that the crankshaft and camshaft sprocket timing marks are dot to dot. L. Loosen the small diameter balance shaft gear bolt. This is the driven gear and has a TORX drive bolt. M. Remove the camshaft sprocket by taking off the lock nut first, then the two bolts. N. Remove the large diameter balance shaft (drive) gear. 0. Remove the small diameter balance shaft driven gear. P. Clean all sealing surfaces, removing all old gasket material.

Installation of new matched set balance shaft gears:

A. Install driven gear and bolt finger tight. B. Install and align drive gear dot to dot with timing mark of the driven gear. C. Install drive gear stud to 16 N.m (12 ft.lbs.) to ensure the shoulder of the stud is below the counter bore in the gear. D. Install camshaft sprocket and chain. Ensure their timing is correct. If the camshaft and crankshaft have not been disturbed, the crankshaft and camshaft sprockets should be dot to dot. E. Install the camshaft sprocket nut and bolts. Torque to 28 N.m (21 ft.lbs.). F. Torque driven balance shaft gear bolt to 20 N.m.(15 ft.lbs.) plus an additional 35 degrees using special tool J36660. G. At this point, the gear change is complete. Follow the removal steps in reverse order to install the remaining components. Consult the service manual for torque specifications.

#### CORRECTION:

2. The following steps should be followed to diagnose the detonation type rattle noise which occurs between 2000 - 2500 RPM under load (condition #2):

a. Ensure the ESC (Electronic Spark Control) system is working properly. Refer to the ELECTRONIC SPARK CONTROL section of the LIGHT DUTY TRUCK FUEL AND EMISSIONS section of the service manual. This section includes an "ELECTRONIC SPARK CONTROL SYSTEM CHECK" with a fault tree for the 4.3L CPI engine. b. Operate the vehicle with premium fuel. If the noise is eliminated, the noise is not coming from the balance shaft rear needle bearing. Refer to the DRIVEABILITY SYMPTOMS section of the LIGHT DUTY TRUCK FUEL AND EMISSIONS service manual. C. If the ESC system is functioning properly and the noise is still audible using premium fuel, the source of the noise is most probably the rear needle bearing of the balance shaft. d. To eliminate the possibility of the rear needle bearing rattling, a production running change was made in early May 1992, to a different type bearing. The needle bearing was changed to a journal type sleeve bearing (much like a camshaft bearing). This type bearing requires pressure fed oil, therefore, an engine block casting change was made to allow an oil passage to be drilled from the vertical oil gallery coming from the oil filter to the rear balance shaft journal. e. If the detonation type rattle noise is unacceptable to the customer, the engine must be replaced using an SPO Goodwrench engine assembly part number 12520408.

#### IMPORTANT: The original needle bearing engine must be scrapped. Dealers found not conforming to this Corporate Policy will be subject to incurring the cost of the warranty claim.

f. MEM-CAL Information: When replacing a 1992 needle bearing engine (only produced prior to the May 1992 VIN break- points) with a sleeve bearing engine, the MEM-CAL must be updated to the later 1992 version. See part number information below. These new MEM-CALs are required to change the ESC calibration for the sleeve bearing engine. Without the correct calibration MEM-CAL, the engine will detonate.

g. ESC (Electronic Spark Control) information: The sleeve bearing engine "sounds" different to the ESC system. To make the sleeve bearing engine operate properly the 1992 M and L van vehicles, the knock sensors and locations have changed. The 1992 M/L motors require only one 3900 ohm knock sensor mounted in the transmission flange close to the distributor. Connect the knock sensor harness to the knock sensor in the transmission flange. The second knock sensor connector harness at the middle of the right cylinder head will not be used on the 1992 model year M and L vans with the sleeve bearing engines. To ensure the harness does not lie on the exhaust manifold and short out, tie the connector back onto the harness using a plastic tie strap. The S and T trucks will continue using both 8200 ohm knock sensors with the sleeve bearing engine. No modification to the existing harness is necessary.

SLEEVE BEARING BALANCE SHAFT KNOCK SENSOR INFORMATION:

Number of Knock Sensor Vehicle Knock Sensors Location M/L 1 Transmission Flange S/T 2 Cylinder Heads

VIN BREAKPOINTS FOR SLEEVE BEARING ENGINES BEGINNING WITH:

Plant Application VIN Number

Baltimore M Van Chevrolet 1GNDM15W3NB205128 M Van GMC 1GDDMl9W7NB539239 L Van Chevrolet 1GNELL9W3NB205177 L Van GMC 1GKEL19WlNB539267

Moraine S/T Chevrolet 1GNDT13W4N2201921 S/T GMC 1GKDTI3W4N2530843 S/T OLDS 1GHDT13W7N2709741

Shreveport S/T Chevrolet 1GCCS19RON8194634 S/T GMC 1GTDT19W6N8519794

Pontiac West S Chevrolet 1GNCS18WlNOl48128 S GMC 1GKCS18W4NO514578 T Chevrolet 1GNCT18W2NO148331 T GMC 1GKCT18W4NO514576

ENGINE BROADCAST CODE INFORMATION (last three digits of the engine I.D. number located in front of the right cylinder head at deck height):

Sleeve Bearing Needle Bearing Engine Vehicle Engine (Produced prior to VIN breakpoints) M XCU XCN L SCT XCD S XJF XFK T XJH XFW Goodwrench XXJ Not Produced

#### WARRANTY INFORMATION:

Condition 1 - For vehicles repaired by changing balance shaft drive gears: Labour Operation: J0880 Labour Time: Series Code M L S T Hours 2.2 2.2 2.8 2.8 With skid plate, add 0.2 0.2

Condition 2 - For vehicles repaired by exchanging engines: Labour Operation: J1840 Labour Time: (in hours) Description Vehicle Series Code M L S T MEM-CAL 0.6 0.6 0.8 0.8 Replace Engine Assembly 8.4 9.6 7.3 7.8 ADD TIME: With Air Conditioning 1.0 0.1 0.2 0.2 With Cruise Control 0.2 0.2 - - With Automatic Transmission 0.3 0.3 0.1 0.1

#### NOTE: Applicable miscellaneous items, such as engine oil and engine coolant, should be added to the above part allowance amount and included in the Net Amount (DMN) column of the claim.

#### PART INFORMATION:

GMSPO Goodwrench Engine Assembly for L35-Equipped Vehicles: 12520408

#### Content:

Cylinder and case, cylinder head assembly, crankshaft, crankshaft main and rod bearings, piston and connecting rod assembly, T-Truck/L-Van oil pan and screen assembly, camshaft, valve lifters, push rods, camshaft chain and sprockets, balance shaft, balance shaft drive gears, valve lifter retainer, front cover and pointer, valve rocker cover, oil fill rap, harmonic balancer.

Additional Parts Required to Dress-Out the Goodwrench Engines: (Quantity: 1 each, except as noted)

Part Description M L S T

Intake Manifold Gasket 12510908 12510908 12510908 12510908 Kit

Knock Sensor(s) 10456031 10456031 10456082 10456082 10456146 10456146

Oil Pan (Use old oil 10054809 Included 10172791 Included pan, if possible)

Oil Pump Screen Assembly 03764113 Included 10054774 Included (Use old oil pump, if possible)

Water Pump Gasket 03754587 03754587 03754587 03754587 (2 required)

Oil Filter Adapter 10108436 10108436 10108436 10172754 Gasket

Oil Filter Adapter Seal 03727474 03727474 03727474 03727474

Bolt-Engine Mounting 15688341 15688341 09442119 09442119 Bracket (6 required)

DO NOT REUSE P/N 15688341. The M/L Van requires the use of this bolt to allow the engine assembly to break free of its mounts in a very extreme frontal collision situation.

MEM-CAL (See calibration information listed below)

CALIBRATION INFORMATION FOR 1992 MODEL YEAR VEHICLES WITH SLEEVE BEARING ENGINES:

SPO PROM Scanner Broadcast Vehicle Part No. ID Code Series Emissions

16181241 1101 BCBB M1 Federal and High Altitude 16181249 1111 BCBC L1 Federal and High Altitude 16181255 1121 BCBD Mi California 16181261 1131 BCBF L1 California 16181277 1141 BCBH S1,T1 Federal and California except California S1 16181281 1151 BCBJ S1 California Sl pickup truck (2WD)

TORQUE SPECIFICATIONS: N.m Ft. Lbs. In. Lbs.

Lower Intake Manifold Bolts 48 35 -

Upper Intake Manifold Bolts 10 - 88

Exhaust Manifold Bolts Center Two Bolts 36 26 - All Others 28 20 -

Knock Sensor(s) 19 14 -

Water Pump Bolts 40 30 -

Flex Plate Bolts 100 75 -

Oil Pump Bolts 90 65 -

Oil Pan Nuts 23 17 -

Oil Pan Bolts 11 - 97

Oil Filter Adapter Bolts 20 15 -

Engine Mounting Bracket Bolts (Refer to Service Manual Section 6A3 for specific instructions and torque values and sequences.)

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.