Home ReviewsRefund Car not listed?
Home/Jeep/Commander/Jeep Commander I (2005-2010)/Repair manual/Mechanical/3.7L Engine - Service Information: Diagnosis
Contents Wiring diagrams Section: Mechanical All sections

3.7L Engine - Service Information: Diagnosis Jeep Commander I

Mechanical 15 illustrations ~1723 words

ENGINE PERFORMANCE DIAGNOSTIC TABLE

CONDITIONPOSSIBLE CAUSECORRECTION
ENGINE WILL NOT START1. Weak battery1. Charge or replace as necessary.
2. Corroded or loose battery connections.2. Clean and tighten battery connections. Apply a coat of light mineral grease to the terminals.
3. Faulty starter.3. Refer to DIAGNOSIS AND TESTING .
4. Faulty coil or control unit.4. Refer to REMOVAL .
5. Incorrect spark plug gap.5. Correct as necessary.
6. Incorrect right bank cam timing.6. Refer to VALVE TIMING .
7. Dirt or water in fuel system.7. Clean system and replace fuel filter.
8. Faulty fuel pump, relay or wiring.8. Repair or replace as necessary.
9. Faulty cam or crank sensor9. Refer to IGNITION SYSTEM - SERVICE INFORMATION article.
ENGINE STALLS OR ROUGH IDLE1. Vacuum leak.1. Inspect intake manifold and vacuum hoses, repair or replace as necessary.
2. Faulty crank position sensor2. Replace crank position sensor
3. Faulty coil.3. Refer to REMOVAL .
4. Incorrect cam timing.4. See STANDARD PROCEDURE .
ENGINE LOSS OF POWER1. Dirty or incorrectly gapped spark plugs.1. Correct as necessary.
2. Dirt or water in fuel system.2. Clean system and replace fuel filter.
3. Faulty fuel pump.3. Refer to DESCRIPTION .
4. Blown cylinder head gasket.4. Replace cylinder head gasket.
5. Low compression.5. See CYLINDER COMPRESSION PRESSURE LEAKAGE , repair as necessary.
6. Burned, warped or pitted valves.6. Replace as necessary.
7. Plugged or restricted exhaust system.7. Inspect and replace as necessary.
8. Faulty coil.8. Refer to REMOVAL .
9. Incorrect cam timing.9. Refer to VALVE TIMING .
ENGINE MISSES ON ACCELERATION1. Spark plugs dirty or incorrectly gapped.1. Correct as necessary.
2. Dirt in fuel system.2. Clean fuel system.
3. Burned, warped or pitted valves.3. Replace as necessary.
4. Faulty coil.4. Refer to REMOVAL .
ENGINE MISSES AT HIGH SPEED1. Spark plugs dirty or incorrectly gapped.1. Correct as necessary.
2. Faulty coil.2. Refer to REMOVAL .
3. Dirt or water in fuel system.3. Clean system and replace fuel filter.

ENGINE PERFORMANCE DIAGNOSTIC

ENGINE LUBRICATION DIAGNOSTIC TABLE

CONDITIONPOSSIBLE CAUSESCORRECTION
OIL LEAKS1. Gaskets and O-Rings. Misaligned or damaged.1. Replace as necessary.
(a) Loose fasteners, broken or porous metal parts.(a) Tighten fasteners, Repair or replace metal parts.
2. Crankshaft rear seal2. Replace as necessary. See REMOVAL .
3. Crankshaft seal flange. Scratched, nicked or grooved.3. Polish or replace crankshaft.
4. Oil pan flange cracked.4. Replace oil pan. See REMOVAL .
5. Timing chain cover seal, damaged or misaligned.5. Replace seal. See REMOVAL .
6. Scratched or damaged vibration damper hub.6. Polish or replace damper.
OIL PRESSURE DROP1. Low oil level.1. Check and correct oil level.
2. Faulty oil pressure sending unit.2. Replace sending unit. See REMOVAL .
3. Low oil pressure.3. Check oil pump and bearing clearance.
4. Clogged oil filter.4. Replace oil filter. See REMOVAL .
5. Worn oil pump.5. Replace oil pump. See REMOVAL .
6. Thin or diluted oil.6. Change oil and filter.
7. Excessive bearing clearance.7. Replace as necessary.
8. Oil pump relief valve stuck.8. Replace oil pump. See REMOVAL .
9. Oil pick up tube loose, damaged or clogged.9. Replace as necessary.
OIL PUMPING AT RINGS; SPARK PLUGS FOULING1. Worn or damaged rings.1. Hone cylinder bores and replace rings.
2. Carbon in oil ring slots.2. Replace rings. See STANDARD PROCEDURE .
3. Incorrect ring size installed.3. Replace rings. See STANDARD PROCEDURE .
4. Worn valve guides.4. Ream guides and replace valves. See REMOVAL .
5. Leaking valve guide seals.5. Replace valve guide seals.

ENGINE LUBRICATION DIAGNOSTIC

ENGINE MECHANICAL DIAGNOSTIC TABLE

CONDITIONPOSSIBLE CAUSESCORRECTIONS
NOISY VALVES1. High or low oil level in crankcase.1. See STANDARD PROCEDURE .
2. Thin or diluted oil.2. Change oil and filter.
3. Low oil pressure.3. Check oil pump, if OK, check rod and main bearings for excessive wear.
4. Dirt in lash adjusters.4. Replace as necessary.
5. Worn rocker arms.5. Replace as necessary.
6. Worn lash adjusters6. Replace as necessary.
7. Worn valve guides.7. See STANDARD PROCEDURE .
8. Excessive runout of valve seats on valve faces.8. See STANDARD PROCEDURE .
CONNECTING ROD NOISE1. Insufficient oil supply.1. See STANDARD PROCEDURE .
2. Low oil pressure.2. Check oil pump, if OK, check rod and main bearings for excessive wear.
3. Thin or diluted oil.3. Change oil and filter.
4. Excessive bearing clearance.4. Replace as necessary.
5. Connecting rod journal out-of-round.5. Service or replace crankshaft.
6. Misaligned connecting rods.6. Replace bent connecting rods.
MAIN BEARING NOISE1. Insufficient oil supply.1. See STANDARD PROCEDURE .
2. Low oil pressure.2. Check oil pump, if OK, check rod and main bearings for excessive wear.
3. Thin or diluted oil.3. Change oil and filter.
4. Excessive bearing clearance.4. Replace as necessary.
5. Excessive end play.5. Check thrust washers for wear.
6. Crankshaft journal out-of round.6. Service or replace crankshaft.
7. Loose flywheel or torque converter.7. Tighten to correct torque

ENGINE MECHANICAL DIAGNOSTIC

CYLINDER-TO-CYLINDER LEAKAGE TEST

To determine if an engine cylinder head gasket is leaking between adjacent cylinders, follow the procedures in Cylinder Compression Pressure Test. See CYLINDER COMPRESSION PRESSURE LEAKAGE . An engine cylinder head gasket leaking between adjacent cylinders will result in approximately a 50 - 70% reduction in compression pressure.

CYLINDER-TO-WATER JACKET LEAKAGE TEST

WARNINGUSE EXTREME CAUTION WHEN THE ENGINE IS OPERATING WITH COOLANT PRESSURE CAP REMOVED.

VISUAL TEST METHOD

With the engine cool, remove the coolant pressure cap. Start the engine and allow it to warm up until thermostat opens.

If a large combustion/compression pressure leak exists, bubbles will be visible in the coolant.

CHEMICAL TEST METHOD

Combustion leaks into the cooling system can also be checked by using Bloc-Chek Kit C-3685-A or equivalent. Perform test following the procedures supplied with the tool kit.

Scheme 35

Scheme 35: CYLINDER HEAD - LEFT
Scheme 35: CYLINDER HEAD - LEFT

Scheme 36

Scheme 36
Scheme 36

Scheme 37

Scheme 37
Scheme 37

Scheme 38

Scheme 38
Scheme 38
  1. Disconnect the negative cable from the battery.
  2. Raise the vehicle on a hoist.
  3. Disconnect the exhaust pipe at the left side exhaust manifold.
  4. Drain the engine coolant. Refer to «STANDARD PROCEDURE»(ref-288235-S07920148752008062000000) .
  5. Lower the vehicle.
  6. Remove the intake manifold. See «REMOVAL»(ref-288233-S36083521932008062000000) .
  7. Remove the master cylinder and booster assembly. Refer to «REMOVAL»(ref-288221-S24180490342008062000000) .
  8. Remove the cylinder head cover. See «REMOVAL»(ref-288233-S18136598952008062000000) .
  9. Remove the fan shroud and fan blade assembly. Refer to «REMOVAL»(ref-288235-S14612409552008062000000) .
  10. Remove the accessory drive belt. Refer to «REMOVAL»(ref-288235-S32167489122008062000000) .
  11. Remove the power steering pump and set aside.
  12. Rotate the crankshaft until the damper timing mark is aligned with TDC indicator mark (2).
  13. Verify the V6 mark (1) on the camshaft sprocket is at the 12 o'clock position, with the No. 1 cylinder at TDC on the exhaust stroke. Rotate the crankshaft one turn if necessary.
  14. Remove the vibration damper. See «REMOVAL»(ref-288233-S33751415912008062000000) .
  15. Remove the timing chain cover. See «REMOVAL»(ref-288233-S38983476322008062000000) .
  16. Lock the secondary timing chains (2) to the idler sprocket using Secondary Camshaft Chain Holder 8429 (1). NOTE: Mark the secondary timing chain prior to removal to aid in installation.
  17. Mark the secondary timing chain (2), one link on each side of the V6 mark on the camshaft drive gear.
  18. Remove the left side secondary chain tensioner. See «REMOVAL»(ref-288233-S42264196592008062000000) .
  19. Remove the cylinder head access plug (1) and (2).
  20. Remove the left side secondary chain guide. See «REMOVAL»(ref-288233-S42264196592008062000000) .
  21. Remove the retaining bolt and the camshaft drive gear. CAUTION: Do not allow the engine to rotate. Severe damage to the valve train can occur. CAUTION: Do not overlook the four smaller bolts at the front of the cylinder head. Do not attempt to remove the cylinder head without removing these four bolts. NOTE: The cylinder head is attached to the cylinder block with twelve bolts.
  22. Remove the cylinder head retaining bolts.
  23. Remove the cylinder head and gasket. Discard the gasket.
CAUTIONDo not lay the cylinder head on its gasket sealing surface, due to the design of the cylinder head gasket any distortion to the cylinder head sealing surface may prevent the gasket from properly sealing resulting in leaks.

Scheme 39

Scheme 39: CYLINDER HEAD - RIGHT
Scheme 39: CYLINDER HEAD - RIGHT
1 - TIMING CHAIN COVER
2 - CRANKSHAFT TIMING MARKS

Scheme 40

Scheme 40
Scheme 40

Scheme 41

Scheme 41
Scheme 41

Scheme 42

Scheme 42
Scheme 42

Scheme 43

Scheme 43
Scheme 43
  1. Disconnect battery negative cable.
  2. Raise the vehicle on a hoist.
  3. Disconnect the exhaust pipe at the right side exhaust manifold.
  4. Drain the engine coolant. Refer to «STANDARD PROCEDURE»(ref-288235-S07920148752008062000000).
  5. Lower the vehicle.
  6. Remove the intake manifold. See «REMOVAL»(ref-288233-S36083521932008062000000).
  7. Remove the cylinder head cover. See «REMOVAL»(ref-288233-S27162136862008062000000).
  8. Remove the fan shroud. Refer to «REMOVAL»(ref-288235-S14612409552008062000000).
  9. Remove oil fill housing from cylinder head.
  10. Remove accessory drive belt. Refer to «REMOVAL»(ref-288235-S32167489122008062000000).
  11. Rotate the crankshaft until the damper timing mark is aligned with TDC indicator mark (2). (Scheme 40)
  12. Verify the V6 mark on the camshaft sprocket is at the 12 o'clock position. (Scheme 41) Rotate the crankshaft one turn if necessary.
  13. Remove the crankshaft damper. See «REMOVAL»(ref-288233-S33751415912008062000000).
  14. Remove the timing chain cover. See «REMOVAL»(ref-288233-S38983476322008062000000). 1 - SPECIAL TOOL 8429 2 - CAMSHAFT CHAIN 3 - CRANKSHAFT TIMING GEAR
  15. Lock the secondary timing chains to the idler sprocket using the Secondary Camshaft Chain Holder 8429 (1). (Scheme 42) NOTE: Mark the secondary timing chain prior to removal to aid in installation.
  16. Mark the secondary timing chain, one link on each side of the V6 mark on the camshaft drive gear.
  17. Remove the right side secondary chain tensioner. See «REMOVAL»(ref-288233-S42264196592008062000000). 1 - RIGHT CYLINDER HEAD ACCESS PLUG 2 - LEFT CYLINDER HEAD ACCESS PLUG
  18. Remove the cylinder head access plug (1, 2). (Scheme 43)
  19. Remove the right side secondary chain guide. See «REMOVAL»(ref-288233-S42264196592008062000000). CAUTION: The nut on the right side camshaft sprocket should not be removed for any reason, as the sprocket and camshaft sensor target wheel is serviced as an assembly. If the nut was removed, tighten nut to 5 N.m (44 in. lbs.).
  20. Remove the retaining bolt and the camshaft drive gear. CAUTION: Do not allow the engine to rotate. severe damage to the valve train can occur. CAUTION: Do not overlook the four smaller bolts at the front of the cylinder head. Do not attempt to remove the cylinder head without removing these four bolts. CAUTION: Do not hold or pry on the camshaft target wheel for any reason. A damaged target wheel can result in a vehicle no start condition. * - INDICATES SEALANT ON THREADS NOTE: The cylinder head is attached to the cylinder block with twelve bolts.
  21. Remove the cylinder head retaining bolts. see scheme 68
  22. Remove the cylinder head and gasket. Discard the gasket.
CAUTIONDo not lay the cylinder head on its gasket sealing surface, do to the design of the cylinder head gasket any distortion to the cylinder head sealing surface may prevent the gasket from properly sealing resulting in leaks.

INSPECTION

Wipe the inserts clean and inspect for abnormal wear patterns and for metal or other foreign material imbedded in the lining. Normal main bearing insert wear patterns are illustrated.

Inspect the back of the inserts for fractures, scrapes, or irregular wear patterns.

Inspect the upper insert locking tabs for damage.

Replace all damaged or worn bearing inserts.

Air Leak Detection Test Method

  1. Disconnect the breather cap to air cleaner hose at the breather cap end. Cap or plug breather cap nipple.
  2. Remove the PCV valve from the cylinder head cover. Cap or plug the PCV valve grommet.
  3. Attach an air hose with pressure gauge and regulator to the dipstick tube. CAUTION: Do not subject the engine assembly to more than 20.6 kPa (3 PSI) of test pressure.
  4. Gradually apply air pressure from 1 psi to 2.5 psi maximum while applying soapy water at the suspected source. Adjust the regulator to the suitable test pressure that provide the best bubbles which will pinpoint the leak source. If the oil leak is detected and identified, repair per service information procedures.
  5. If the leakage occurs at the rear oil seal area, refer to «REAR SEAL AREA LEAKS»(ref-288233-S11067216972008062000000) .
  6. If no leaks are detected, turn off the air supply and remove the air hose and all plugs and caps. Install the PCV valve and breather cap hose.
  7. Clean the oil off the suspect oil leak area using a suitable solvent. Drive the vehicle at various speeds approximately 24 km (15 miles). Inspect the engine for signs of an oil leak by using a black light.

INSPECTION FOR REAR SEAL AREA LEAKS

Since it is sometimes difficult to determine the source of an oil leak in the rear seal area of the engine, a more involved inspection is necessary. The following steps should be followed to help pinpoint the source of the leak.

If the leakage occurs at the crankshaft rear oil seal area

  1. Disconnect the battery.
  2. Raise the vehicle.
  3. Remove torque converter or clutch housing cover and inspect rear of block for evidence of oil. Use a black light to check for the oil leak: Circular spray pattern generally indicates seal leakage or crankshaft damage. Where leakage tends to run straight down, possible causes are a porous block, distributor seal, camshaft bore cup plugs oil galley pipe plugs, oil filter runoff, and main bearing cap to cylinder block mating surfaces.
  4. If no leaks are detected, pressurize the crankcase as outlined in «AIR LEAK DETECTION TEST METHOD»(ref-288233-S15168912682008062000000) . CAUTION: Do not exceed 20.6 kPa (3 psi).
  5. If the leak is not detected, very slowly turn the crankshaft and watch for leakage. If a leak is detected between the crankshaft and seal while slowly turning the crankshaft, it is possible the crankshaft seal surface is damaged. The seal area on the crankshaft could have minor nicks or scratches that can be polished out with emery cloth. CAUTION: Use extreme caution when crankshaft polishing is necessary to remove minor nicks and scratches. The crankshaft seal flange is especially machined to complement the function of the rear oil seal.
  6. For bubbles that remain steady with shaft rotation, no further inspection can be done until disassembled.

Scheme 44

Scheme 44: ENGINE OIL PAN
Scheme 44: ENGINE OIL PAN

The engine oil pan (1) is made of laminated steel and has a single plane sealing surface. The sandwich style oil pan gasket has an integrated windage tray (2) and steel carrier. The sealing area of the gasket is molded with rubber and is designed to be reused as long as the gasket is not cut, torn or ripped.

Scheme 45

Scheme 45: OIL PAN
Scheme 45: OIL PAN

Scheme 46

Scheme 46
Scheme 46

Scheme 47

Scheme 47
Scheme 47

Scheme 48

Scheme 48
Scheme 48

Scheme 49

Scheme 49
Scheme 49
  1. Disconnect negative battery cable.
  2. Remove the radiator fan. Refer to «REMOVAL»(ref-288235-S14612409552008062000000) .
  3. Remove the intake manifold. See «REMOVAL»(ref-288233-S36083521932008062000000) .
  4. Install Special Tool #8534 Do not raise engine at this time.
  5. Remove the structural cove using sequence shown in illustration. See «REMOVAL»(ref-288233-S29828238662008062000000) .
  6. Remove both left and right side engine mount through bolts (3).
  7. Raise engine using Engine Support 8534 (1), to provide clearance to remove oil pan.
  8. Drain engine oil and remove oil filter. NOTE: Do not pry on oil pan or oil pan gasket. Gasket is mounted to engine and does not come out with oil pan.
  9. Remove the oil pan mounting bolts and oil pan.
  10. Unbolt oil pump pickup tube and remove tube and oil pan gasket from engine.

CRANKCASE OIL LEVEL INSPECTION

CAUTIONDo not overfill crankcase with engine oil, pressure loss or oil foaming can result.

Inspect engine oil level approximately every 800 kilometers (500 miles). Unless the engine has exhibited loss of oil pressure, run the engine for about five minutes before checking oil level. Checking engine oil level on a cold engine is not accurate.

To ensure proper lubrication of the engine, the engine oil must be maintained at an acceptable level. The acceptable levels are indicated between the ADD and SAFE marks on the engine oil dipstick.

  1. Position vehicle on level surface.
  2. With engine OFF, allow approximately ten minutes for oil to settle to bottom of crankcase, remove engine oil dipstick.
  3. Wipe dipstick clean.
  4. Install dipstick and verify it is seated in the tube.
  5. Remove dipstick, with handle held above the tip, take oil level reading.
  6. Add oil only if level is below the ADD mark on dipstick.

More articles — 3.7L Engine - Service Information