Engine Mechanical - 4.2L: Diagnosis GMC Envoy II

Diagnostic Starting Point - Engine Mechanical

Begin the system diagnosis by reviewing the Disassembled Views , Engine Component Description , and Lubrication Description . Reviewing the description and operation information will help you determine the correct symptom diagnostic procedure when a malfunction exists. Reviewing the description and operation information will also help you determine if the condition described by the customer is normal operation. Refer to Symptoms - Engine Mechanical in order to identify the correct procedure for diagnosing the system and where the procedure is located.

Strategy Based Diagnostics

1. Perform A Diagnostic System Check in Engine Controls before using the symptom tables (if applicable).
2. Review the system operations in order to familiarize yourself with the system functions. Refer to «Disassembled Views»(ref-200396-S36199845132005102000000) , «Engine Component Description»(ref-200396-S39686314502005102000000) , and «Lubrication Description»(ref-200396-S05157715212005102000000) .

All diagnosis on a vehicle should follow a logical process. Strategy based diagnostics is a uniform approach for repairing all systems. The diagnostic flow may always be used in order to resolve a system problem. The diagnostic flow is the place to start when repairs are necessary.

Visual/Physical Inspection

1. Inspect for aftermarket devices which could affect the operation of the engine.
2. Inspect the easily accessible or visible system components for obvious damage or conditions which could cause the symptom.
3. Check for the correct oil level, proper oil viscosity, and correct filter application.
4. Verify the exact operating conditions under which the concern exists. Note factors such as engine RPM, ambient temperature, engine temperature, amount of engine warm-up time, and other specifics.
5. Compare the engine sounds (if applicable) to a known good engine and make sure you are not trying to correct a normal condition.

Symptom List

Refer to a symptom diagnostic procedure from the following list in order to diagnose the symptom

1. «Base Engine Misfire without Internal Engine Noises»(ref-200396-S39282391022005102000000)
2. «Base Engine Misfire with Abnormal Internal Lower Engine Noises»(ref-200396-S04293786952005102000000)
3. «Base Engine Misfire with Abnormal Valve Train Noise»(ref-200396-S06913237082005102000000)
4. «Base Engine Misfire with Coolant Consumption»(ref-200396-S33412423152005102000000)
5. «Base Engine Misfire with Excessive Oil Consumption»(ref-200396-S04270240042005102000000)
6. «Engine Compression Test»(ref-200396-S26481969892005102000000)
7. «Engine Noise on Start-Up, but Only Lasting a Few Seconds»(ref-200396-S39565351992005102000000)
8. «Upper Engine Noise, Regardless of Engine Speed»(ref-200396-S05827234052005102000000)
9. «Lower Engine Noise, Regardless of Engine Speed»(ref-200396-S19839392782005102000000)
10. «Engine Noise Under Load»(ref-200396-S02109750892005102000000)
11. «Engine Will Not Crank - Crankshaft Will Not Rotate»(ref-200396-S17828510472005102000000)
12. «Oil Consumption Diagnosis»(ref-200396-S40113198152005102000000)
13. «Oil Pressure Diagnosis and Testing»(ref-200396-S05176206452005102000000)
14. «Oil Leak Diagnosis»(ref-200396-S03470846452005102000000)

Oil Consumption Diagnosis

Oil Consumption Diagnosis

Oil Pressure Diagnosis and Testing

Tools Required

1. J 21867 Pressure Gage and Hose Assembly. See «Special Tools»(ref-200396-S26818425802005102000000) .
2. J 42907 Oil Pressure Tester. See «Special Tools»(ref-200396-S26818425802005102000000) .

1. With the vehicle on a level surface, run the vehicle for a few minutes, allow adequate drain down time (2-3 minutes) and measure for a low oil level.
2. If required, add the recommended grade engine oil and fill the crankcase until the oil level measures full on the oil level indicator.
3. Run the engine briefly (10-15 seconds) and verify low or no oil pressure on the vehicle gage or light.
4. Listen for a noisy valve train or a knocking noise.
5. Inspect for the following: Oil diluted by water or glycol (anti freeze) Foamy oil
6. Remove the oil filter and install the J 42907 . See «Special Tools»(ref-200396-S26818425802005102000000) .
7. Install J 21867 or equivalent to the J 42907 . See «Special Tools»(ref-200396-S26818425802005102000000) .
8. Run the engine and measure the engine oil pressure.
9. Compare the readings to «Engine Mechanical Specifications»(ref-200396-S04002696082005102000000) .
10. If the engine oil pressure is below specifications, inspect the engine for one or more of the following: Oil pump worn or dirty Refer to «Oil Pump Cleaning and Inspection»(ref-200396-S31190679032005102000000) . Oil pump screen loose, plugged, or damaged Oil pump screen O-ring seal missing or damaged Malfunctioning oil pump pressure regulator valve Excessive bearing clearance Cracked, porous, or restricted oil galleries Oil gallery plugs missing or incorrectly installed Refer to «Engine Block Plug Installation»(ref-200396-S32239435842005102000000) . Broken valve lash adjusters Repair as necessary
11. If the reading on J 21867 or equivalent is within specifications, inspect for the following:. See «Special Tools»(ref-200396-S26818425802005102000000) . Plugged or incorrect oil filter and/or malfunctioning oil bypass valve Malfunctioning vehicle oil pressure gage or sensor Repair as necessary

Oil Leak Diagnosis

Oil Leak Diagnosis

Diagnostic Aids

The symptom may be intermittent due to moisture on the drive belt(s) or the pulleys. It may be necessary to spray a small amount of water on the drive belt(s) in order to duplicate the customers concern. If spraying water on the drive belt(s) duplicates the symptom, cleaning the belt pulleys may be the probable solution.

A loose or improper installation of a body component, a suspension component, or other items of the vehicle may cause the chirping noise.

A loose or improper installation of a body component, a suspension component, or other items of the vehicle may cause the squeal noise.

If the noise is intermittent, verify the accessory drive components by varying their loads making sure they are operated to their maximum capacity. An overcharged A/C system, power steering system with a pinched hose or wrong fluid, or a generator failing are suggested items to inspect.

The drive belt(s) will not cause the whine noise.

If the whine noise is intermittent, verify the accessory drive components by varying their loads making sure they are operated to their maximum capacity. Such items but not limited to may be an A/C system overcharged, the power steering system restricted or the wrong fluid, or the generator failing.

Vibration from the engine operating may cause a body component or another part of the vehicle to make rumbling noise.

The drive belt(s) may have a condition that can not be seen or felt. Sometimes replacing the drive belt may be the only repair for the symptom.

If replacing the drive belt(s), completing the diagnostic table, and the noise is only heard when the drive belt(s) is installed, there might be an accessory drive component with a failure. Varying the load on the different accessory drive components may aid in identifying which component is causing the rumbling noise.

The accessory drive components can have an affect on engine vibration. Such as but not limited to the A/C system over charged, the power steering system restricted or the incorrect fluid, or an extra load on the generator. To help identify an intermittent or an improper condition, vary the loads on the accessory drive components.

If the drive belt(s) repeatedly falls off the drive belt pulleys, this is because of pulley misalignment.

An extra load that is quickly applied on released by an accessory drive component may cause the drive belt to fall off the pulleys. Verify the accessory drive components operate properly.

If the drive belt(s) is the incorrect length, the drive belt tensioner may not keep the proper tension on the drive belt.

Excessive wear on a drive belt(s) is usually caused by an incorrect installation or the wrong drive belt for the application.

Minor misalignment of the drive belt pulleys will not cause excessive wear, but will probably cause the drive belt(s) to make a noise or to fall off.

Excessive misalignment of the drive belt pulleys will cause excessive wear but may also make the drive belt(s) fall off.

Inspection Procedure

1. Remove the drive belts. Refer to «Drive Belt Replacement»(ref-200396-S20666880032005102000000) .
2. Position a hex-head socket on the belt tensioner pulley bolt head.
3. Move the drive belt tensioner through it's full travel. The movement should feel smooth. There should be no binding. The tensioner should return freely.
4. If any binding is observed, replace the tensioner. Refer to «Drive Belt Tensioner Replacement»(ref-200396-S30481771322005102000000) .
5. Install the drive belt. Refer to «Drive Belt Replacement»(ref-200396-S20666880032005102000000) .

Camshaft Position (CMP) Actuator Diagnosis

For overall description of the camshaft position actuator refer to Exhaust Camshaft Position Actuator Description .

The camshaft position actuator will only phase 25-cam degrees retard (counterclockwise). Full advance (clockwise) is 0 degrees.

Scheme 1

The camshaft position actuator should always be serviced/replaced in the full advanced position (full clockwise or 0 degrees). New replacement (service) camshaft position actuators are shipped at full advance or 0 degrees. To be sure the camshaft position actuator is performing properly, perform the following to help in the diagnostics.

The camshaft position actuator must be removed from the engine to perform the proper diagnostic test.

1. Clamp the camshaft actuator in a vice. Use care not to damage the contact area of the sprocket.
2. Scribe or draw a line (1) on the camshaft position actuator outer ring face, in the full advanced position. With the engine at TDC on #1 cylinder, the wording should be level.
3. Apply compressed air pressure to the oil port (1) on the back side of the actuator to unlock the locking pin.
4. Turn the actuator, by hand, to the full counterclockwise position.
5. Scribe or draw a line (2) on the camshaft position actuator at that position.
6. Measure the distance between the two lines. The measurement (3) should be 14-15 mm (0.55-0.59 in). The camshaft position actuator must be replaced if it does not unlock when air pressure is applied, does not lock when air pressure is removed, or does not move within the 14-15 mm (0.55-0.59 in).

Engine Block Cleaning and Inspection

Tools Required

1. J 8001 Dial Indicator Set
2. J 8087 Cylinder Bore Gauge. See «Special Tools»(ref-200396-S26818425802005102000000) .
3. J 45059 Angle Meter. See «Special Tools»(ref-200396-S26818425802005102000000) .

1. Clean the sealing material from all gasket mating surfaces.
2. Clean the engine block with a cleaning solution.
3. Flush the engine block with clean water.
4. Clean the oil passages.
5. Coat the cylinder bores and the machined surfaces with engine oil.
6. Inspect the threaded holes. Clean the holes with a tap, if needed.
7. Use a straight edge and a feeler gauge to check the deck surface for flatness. Carefully remove any minor irregularities. Replace the block if there is more than 0.08 mm (0.003 in) gap.
8. Replace the engine block if the bores are out of specification.
9. Inspect the cylinder bores. Use J 8087 to measure the cylinder bore. See «Special Tools»(ref-200396-S26818425802005102000000) . Inspect the bores for the following conditions: Wear Taper Runout Ridging
10. Leave sufficient material to allow finish honing when fitting the pistons.
11. Inspect the oil pan rail for nicks. Use a flat file to remove an nicks.
12. Inspect the front cover attaching area for nicks. Use a flat file to remove any nicks.
13. Inspect the mating surfaces of the transmission case.
14. Use the following procedure to measure the engine block flange runout at the mounting bolt hole bosses: Temporarily install the crankshaft. Measure the crankshaft flange runout. Hold a gauge plate flat against the crankshaft flange. Place J 8001 (dial indicator stem) on the transmission mounting bolt hole boss. Set the indicator to zero. Record the readings obtained from all of the bolt hole bosses. The measurements should not vary more than 0.25 mm (0.010 in). Recheck the crankshaft flange runout if the readings vary more than 0.25 mm (0.010 in). If the crankshaft flange runout is within the specification, replace the engine block.
15. Remove the crankshaft.
16. Re-install the crankshaft bearing caps, stiffener, and bolts. Tighten: Tighten the crankshaft bearing cap bolts to 25 N.m (18 lb ft). Use J 45059 to tighten the crankshaft bearing cap bolts an additional 180 degrees. See «Special Tools»(ref-200396-S26818425802005102000000) .
17. Inspect the crankshaft main bearing bores. Use J 8087 to measure the bearing bore concentricity and alignment. See «Special Tools»(ref-200396-S26818425802005102000000) .
18. Remove the crankshaft main bearing cap stiffener and main bearing caps with bearings.

Crankshaft and Bearings Cleaning and Inspection

Tools Required

1. J 45059 Angle Meter. See «Special Tools»(ref-200396-S26818425802005102000000) .
2. J 8087 Cylinder Bore Gauge. See «Special Tools»(ref-200396-S26818425802005102000000) .

1. Clean the crankshaft of all elements.
2. Inspect the crankshaft oil passages for obstructions.
3. Inspect the crankshaft for the following conditions: Damaged threads (1) Damaged mounting faces Worn crankshaft pin (2) Wear without any grooves or scratches (3) Grooves or scoring (3) Scratches (3) Pitting or embedded bearing material (3) Overheating (discoloration) (3)
4. Inspect the corresponding crankshaft bearing inserts for embedded material and determine the source of the material.
5. Inspect the outer surfaces of the crankshaft bearings for the following conditions: Wear - surface wear indicates either movement of the insert or high spots in the surrounding material (spot wear) Overheating or discoloration Looseness or rotation indicated by flattened tangs and wear grooves
6. Inspect the crankshaft main bearings for craters or pockets. Flattened sections on the crankshaft bearing halves also indicate fatigue.
7. Inspect the thrust surfaces of the main thrust bearing for the following conditions: Wear Grooving - Grooves are caused by irregularities of the crankshaft thrust surface.
8. Inspect the crankshaft bearings for excessive scoring or discoloration.
9. Inspect the crankshaft bearings for dirt or imbedded debris.
10. Inspect the crankshaft bearings for improper seating indicated by bright, polished sections.
11. Inspect the crankshaft bearings for uneven side-to-side wear. This may indicate a bent crankshaft or a tapered bearing journal.
12. Inspect the connecting rod bearing bores using the following procedure: Tighten the connecting rod bearing cap to specification. Use J 8087 to measure the bearing bore for taper and out-of-round. See «Special Tools»(ref-200396-S26818425802005102000000) . Record the readings. No taper or out-of-round should exist.
13. Measure the crankshaft bearing journal diameter with a micrometer in several places, 90 degrees apart. Average the measurements.
14. Measure the crankshaft bearing journal taper and runout.
15. Install the crankshaft bearing caps.
16. Install the crankshaft main bearing cap stiffener.
17. Install the crankshaft bearing cap bolts. Tighten: Tighten the crankshaft bearing cap bolts to 25 N.m (18 lb ft). Use J 45059 to tighten the crankshaft bearing cap bolts an additional 180 degrees. See «Special Tools»(ref-200396-S26818425802005102000000) .
18. Measure the crankshaft main bearing inside diameter with an inside micrometer.
19. Measure the connecting rod inside diameter in the same direction as the length of the rod with an inside micrometer.
20. If the specified clearances cannot be met, the crankshaft, connecting rods, or block may need to be replaced.

Crankshaft Balancer Cleaning and Inspection

1. Inspect the crankshaft balancer sealing area for grooves, nicks, or burs (1).
2. Inspect the crankshaft balancer belt ribs for dents or damage (2).
3. Replace the crankshaft balancer if damage is present.

Engine Flywheel Cleaning and Inspection

1. Inspect the engine flywheel for cracks (1).
2. Inspect the engine flywheel teeth for damage (2).
3. Replace the engine flywheel if damage is present.

Timing Chain and Sprockets Cleaning and Inspection

1. Inspect the timing chain sprockets for cracks or teeth that are worn, broken, or chipped.
2. Inspect the timing chain for binding or stretching.
3. Inspect the dowel pins for wear or damage
4. Inspect the crankshaft sprocket keyway and the locating dowel pins in the crankshaft for damage.
5. Inspect the timing chain shoe and guide for excessive wear or cracks.
6. Inspect the timing chain tensioner for damage.
7. Replace the timing chain and sprockets if damaged.

Valve Rocker Arm and Valve Lash Adjuster Cleaning and Inspection

1. Clean the valve rocker arms and valve lash adjusters in cleaning solvent.
2. Dry the valve rocker arms and valve lash adjusters with compressed air.
3. Inspect the valve rocker arms for the following conditions: Excessive wear at the valve contact or valve lash adjuster socket area A loose or damaged pin A worn or damaged roller. The roller should rotate freely with no binding or roughness.
4. Inspect the valve lash adjusters for the following conditions: Excessive wear Clogging of the oil passage Damage Collapsed or spongy

Camshaft Cover Cleaning and Inspection

1. Remove and discard the rubber ignition coil seals, and the camshaft cover seal.
2. Clean the camshaft cover with a suitable cleaning solvent.
3. Inspect the camshaft cover for cracks or damage.
4. Inspect the bolt threads for damage.
5. Replace the camshaft cover if necessary.

Oil Pump Cleaning and Inspection

1. Clean all parts of sludge, oil, and varnish by soaking in carburetor cleaner or cleaning solvent.
2. Inspect for foreign material and determine the source of the foreign material.
3. Inspect the oil pump housing and engine front cover for the following conditions: Cracks or casting imperfections Scoring Damaged threads
4. Do not attempt to repair the oil pump housing. Replace the oil pump housing if damage is found.
5. Inspect the oil pump gears for damage.
6. Measure the inner oil pump gear tip clearance in several places.
7. Measure the outer oil pump gear tip clearance in several places.
8. Measure the oil pump gear side clearance.
9. Inspect the pressure regulator valve for the following conditions: Scoring Sticking Burrs - Burrs may be removed using a fine oil stone.
10. Inspect the pressure regulator valve spring for loss of tension or bending. Replace the pressure regulator spring if damaged.
11. Inspect the oil pump pipe pickup tube and screen assembly for the following conditions: Looseness - If the oil pump pipe pickup tube is loose or bent, replace the oil pump pipe pickup tube. Broken wire mesh or screen Inspect the O-ring seal at the base of the oil pump pickup tube for damage.

Oil Pan Cleaning and Inspection

1. Clean the oil pan in solvent. Remove all sludge and debris from the oil pan.
2. Remove all sealing material from the oil pan rails.
3. Inspect the oil pan sealing surfaces for nicks or damage. Remove any minor nicks with a fine flat file.
4. Inspect the threads in the oil drain plug hole.
5. Replace the oil pan if necessary.

Engine Front Cover Cleaning and Inspection

1. Clean the engine front cover with cleaning solvent.
2. Remove all sealing material.
3. Inspect the engine front cover sealing surfaces for nicks or damage. Use a fine flat file to remove any minor nicks.
4. Inspect the engine front cover threaded holes for damage.
5. Repair or replace the engine front cover as necessary.

Intake Manifold Cleaning and Inspection

1. Clean the intake manifold gasket mating surface.
2. Inspect the threads on the retaining bolts.
3. Inspect the intake manifold for cracks.
4. Clean the internal ports of all debris.
5. Replace the intake manifold if necessary.

Exhaust Manifold Cleaning and Inspection

1. Clean the exhaust manifold.
2. Inspect the exhaust manifold for cracks or damage.
3. Inspect the exhaust manifold threads and studs (if necessary).
4. Check the exhaust manifold mating surface for flatness. Use a straight edge and a feeler gauge.
5. Replace the exhaust manifold if necessary.

Water Pump Cleaning and Inspection

1. Remove all sealing material from the sealing surface.
2. Inspect the water pump impeller for damage.
3. Inspect the water pump shaft for looseness.
4. Inspect the threads for damage.
5. Replace the water pump if necessary.