KIA Niro: Engine Mechanical System / Troubleshooting

Symptoms :

Engine misfire with abnormal internal lower engine noises

Suspected area → Remedy

• Worn crankshaft bearings  â†’ Replace the crankshaft and bearings as required.

   

• Loose or out of specification engine flywheel  â†’ Repair or replace the flywheel
  as required.

   

Worn piston rings
(Oil consumption may or may not cause the engine to misfire.) → Inspect the cylinder for a loss of
compression.

Repair or replace as required.

Worn crankshaft thrust bearings→ Replace the crankshaft and
bearings as required

Symptoms :

Engine misfire with abnormal valve train noise

Suspected area → Remedy

Stuck valves
(Carbon buildup on the valve stem) → Repair or replace as required.

Excessive worn or miss-aligned timing chain → Replace the timing chain and sprocket as required.

Worn camshaft lobes →Replace the camshaft.

Symptoms :

Engine misfire with coolant consumption

Suspected area → Remedy

• Faulty cylinder head gasket or other damage to the cylinder head and engine block cooling system → Inspect the cylinder head and engine block for damage to the coolant passages and/or a faulty head gasket.

   

• Coolant consumption may or may not cause the engine to overheat → Repair or replace as required.

   

Symptoms :

Engine misfire with excessive oil consumption

Suspected area → Remedy

Worn valves, guides and / or valve stem oil seals → Repair or replace as required.

Worn piston rings
(Oil consumption may or may not cause the engine to misfire) →

• Inspect the cylinder for a loss
  of compression.

   

• Repair or replace as required.

   

Symptoms :

Engine noise on start-up, but only lasting a few
seconds
(Check and compare with
known good vehicle to determine normal condition.)

Suspected area → Remedy

Incorrect oil viscosity →

• Drain the oil.

• Install the oil of the correct viscosity.

Worn crankshaft thrust bearing →

• Inspect the thrust bearing and crankshaft.

• Repair or replace as required.

Symptoms :

Upper engine noise, regardless of engine speed

Suspected area → Remedy

Low oil pressure →

Repair or replace as required.

Broken valve spring → Replace the valve spring.

Worn or dirty valve lifters → Replace the valve lifters.

Stetched or broken timing chain and/or damaged sprocket teeth → Replace the timing chain and
sprockets.

Worn timing chain tensioner, if applicable →Replace the timing chain tensioner as required.

Worn camshaft lobes →

• Inspect the camshaft lobes.

• Replace the camshaft as required.

Worn valve guides or valve stems → Inspect the valves and valve
guides, then repair or replace as required.

Stuck valves (Carbon on the valve stem or valve seat may cause the valve to stay open.) → Inspect the valves and valve
guides, then repair or replace as required.

Worn drive belt, idler, tensioner and bearing → Replace as required.

Symptoms :

Lower engine noise, regardless of engine speed

Suspected area → Remedy

Low oil pressure → Repair or required.

Loose or damaged flywheel → Repair or replace the flywheel.

Damaged oil pan, contacting the oil pump screen →

• Inspect the oil pan.

• Inspect the oil pump screen.

• Repair or replace as required.

Loose, damaged or blocked oil pump screen →

• Inspect the oil pump screen.

• Repair or replace as required.

Excessive piston-to-cylinder bore clearance →

• Inspect the piston, piston pin and cylinder bore.

• Repair or replace as required.

Excessive piston pin-to-piston clearance →

• Inspect the piston, piston pin and the connecting rod.

• Repair or replace as required.

Excessive connecting rod bearing clearance →

Inspect the following components
and repair or replace as required.

• The connecting rod bearings.

• The connecting rods.

• The crankshaft pin journals.

Excessive crankshaft bearing clearance → Inspect the following components, and repair or replace as required.

• The crankshaft bearings.

• The crankshaft main journals.

• The cylinder block

Incorrect piston, piston pin and connecting rod installation →

• Verify the piston pins and connecting rods are installed correctly.

• Repair as required.

Symptoms :

Engine noise under load

Suspected area → Remedy

Low oil pressure → Repair or replace as required.

Excessive connecting rod bearing clearance → Inspect the following components and repair or replace as required:

• The connecting rod bearings

• The connecting rods

• The crankshaft

Excessive crankshaft bearing clearance → Inspect the following components, and repair or replace as required:

• The crankshaft bearings

• The crankshaft main journals

• The cylinder block

Symptoms :

Engine will not crank.

Crankshaft will not rotate.

Suspected area → Remedy

Hydraulically locked cylinder

• Coolant/antifreeze in cylinder

• Oil in cylinder

• Fuel in cylinder → 1) Remove spark plugs and check
  for fluid.

  2) Inspect for broken head gasket.

  3) Inspect for cracked engine block or cylinder head.

  4) Inspect for a sticking fuel injector and/or leaking fuel regulator.

   

Broken timing chain and/or timing chain gears →1) Inspect timing chain and gears.

2) Repair as required.

Material in cylinder

• Broken valve

• Piston material

• Foreign material → 1) Inspect cylinder for damaged components and/or foreign materials.

  2) Repair or replace as required.

   

Seized crankshaft or connecting rod bearings →1) Inspect crankshaft and connecting rod bearing.

2) Repair as required.

Bent or broken connecting rod  → 1) Inspect connecting rods.

2) Repair as required.

Broken crankshaft → 1) Inspect crankshaft.

2) Repair as required.

Special Service Tools

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