Trouble Shooting

Troubleshooting has to start out simple. Basic troubleshooting focuses on the most common problem areas in auto repair, and provides a good starting point for searching out what repairs need to be made.

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Trouble Shooting

Truck Systems Mobile Mechanics are fully equipped with a variety of tools, equipment and parts necessary to be a mobile workshop for various service and repairs.

Backfire-Exhaust Manifold

When the engine backfires through the exhaust manifold, check for the following, as necessary:

  • Fault with the computerized engine control system
  • Faulty vacuum diverter valve
  • Leaks in the exhaust system
  • Leaks in the vacuum hose system

Backfire-Intake Manifold

When the engine backfires through the intake manifold, check for the following, as necessary:

  • A very lean air/fuel mixture (carburetor equipped)
  • Defective Exhaust Gas Recirculation (EGR) valve
  • Fault with the computerized engine control system
  • Incorrect ignition timing

High Oil Pressure

When the engine presents high oil pressure, check for the following, as necessary:

  • Faulty oil pressure gauge or sender
  • Sticking (closed) oil pressure relief valve
  • Wrong grade of oil

Low Oil Pressure

When the engine presents low oil pressure, check for the following, as necessary:

  • Blocked oil pickup screen or tube
  • Low oil level in the crankcase
  • Malfunctioning or excessive clearance of the oil pump
  • Sticking oil pressure relief valve
  • Very thin engine oil
  • Worn (loose) main, rod or camshaft bearings

Excessive Oil Leakage

When large amounts of oil are noticed under the engine after each operation, check for the following, as necessary:

  • Blocked camshaft bearing drain hole
  • Broken timing chain cover gasket
  • Damaged oil pan gasket or bent oil pan
  • Damaged or broken fuel pump gasket (mechanical pump)
  • Damaged or broken oil filter gasket
  • Damaged or loose valve cover gasket
  • Improperly seated oil pan drain plug
  • Leaking oil pressure sending switch
  • Worn front main oil seal gasket
  • Worn rear main oil seal gasket

Engine Speed Oscillates at Idle

When the engine idle speed will not remain constant, check for the following, as necessary:

  • A blocked Positive Crankcase Ventilation (PCV) valve
  • A blown head gasket
  • A faulty fuel pump
  • A leaky Exhaust Gas Recirculation (EGR) valve
  • A worn camshaft
  • Fault with the computerized engine control system
  • Leaking intake manifold-to-engine gasket
  • Overheating of the cooling system
  • Worn timing gears, chain or sprockets

Heavy Oil Consumption

When the engine is burning large amounts of oil, check for the following, as necessary:

  • Clogged piston ring grooves or oil return slots
  • Damaged valve O-ring seals
  • Damaged valve stem oil deflectors
  • Engine oil level that is too high
  • Engine oil that is too thin
  • Excessive clearance of the main and connecting rods
  • Excessively worn piston ring grooves
  • Improper Positive Crankcase Ventilation (PCV) valve operation
  • Insufficient tension of the piston rings
  • Mismatched rail and expander of the oil ring
  • Non-staggered piston ring gaps
  • Piston rings that are sticking in the grooves
  • Restricted oil drain back holes
  • Reversed (up-side-down) compression rings
  • Scored or worn cylinder walls
  • Too long intake gasket dowels
  • Worn valve stem or guides
  • Wrong size of piston rings

Low Power Output of Engine

When the engine power output is below normal, check for the following, as necessary:

  • A blown head gasket
  • A faulty pressure regulator valve (Automatic Transaxle)
  • A poorly operating diverter valve
  • A slipping clutch disc or unadjusted pedal
  • A worn camshaft
  • Excessive piston-to-bore clearance
  • Fault with the computerized engine control system
  • Leaking of the fuel pump or hoses
  • Leaks in the vacuum system
  • Low fluid level (Automatic Transaxle)
  • Overheating of the cooling system
  • Sticking valve(s) or weak valve spring(s)
  • Unadjusted valve timing
  • Worn piston rings

A dirty windshield causes eye fatigue and can pose a safety hazard. Replace worn blades and get plenty of windshield washer solvent.

Engine Detonation (Dieseling)

When the engine operates beyond the controlled limits, check for the following, as necessary:

  • Clogged fuel delivery system
  • Excessive deposits in the combustion chambers
  • Fault with the computerized engine control system
  • Faulty ignition electrical system components
  • Faulty or loose spark plugs
  • Ignition timing that is too far advanced
  • Inoperative Exhaust Gas Recirculation (EGR) valve
  • Inoperative Positive Crankcase Ventilation (PCV) valve
  • Leaks in the vacuum system
  • Sticking, leaking or broken valves

Connecting Rods

When the connecting rod bearings are constantly making noise, check for the following, as necessary:

  • Connecting rod journal of the crankshaft is out-of-round
  • Incorrectly torqued connecting rod bolts
  • Misaligned connecting rod or cap
  • Missing bearing shell or excessive bearing clearance

Main Bearings

When the main bearings are constantly making noise, check for the following, as necessary:

  • Excessive belt tension
  • Excessive clearance of the main bearings
  • Extreme crankshaft end play
  • Loose damper pulley hub
  • Loose torque converter or flywheel mounting bolts
  • Low oil supply to the main bearings
  • Oval shaped crankshaft journals

Negative Oil Pressure

When the engine presents no oil pressure, check for the following, as necessary:

  • Blocked oil pickup screen or tube
  • Blocked oil pump passages
  • Broken oil pressure gauge or sender
  • Leakage of the internal oil passages
  • Low oil level in the crankcase
  • Malfunctioning oil pump
  • Sticking oil pressure relief valve
  • Worn (loose) camshaft bearings

Pistons and Rings

When the pistons and/rings are constantly making noise, check for the following, as necessary:

  • Broken piston rings
  • Build-up of carbon on the piston(s)
  • Loose or seized piston pin(s)
  • Loose or tight ring side clearance
  • Misaligned connecting rods
  • Out-of-round or tapered cylinder bore
  • Piston-to-cylinder bore clearance is excessive

Poor Acceleration

When the engine experiences poor acceleration characteristics, check for the following, as necessary:

  • Fault with the computerized engine control system
  • Incorrect ignition timing
  • Poorly seated valves

Poor High Speed Operation

When the engine cannot maintain high speed operations, check for the following, as necessary:

  • A faulty fuel pump producing low fuel volume
  • A restriction in the intake manifold
  • A worn distributor shaft
  • Fault with the computerized engine control system
  • Leaking valves or worn valve springs
  • Unadjusted valve timing

Valves

When the valves are constantly noisy, check for the following, as necessary:

  • Bent pushrods
  • Broken valve springs
  • Dirty or worn valve lifters
  • Excessive valve seat or face run-out
  • Excessively worn camshaft lobes
  • Loose rocker arm studs
  • Unadjusted valve lash
  • Worn valve guides

Valve Train

When the valve train is constantly making noise, check for the following, as necessary:

  • Bent or worn pushrods
  • Bent valve(s)
  • Cocked or broken valve springs
  • Damaged lifter plunger or pushrod seat
  • Dirt or chips in the valve lifters
  • Excessive valve lifter leak down
  • Excessive valve stem-to-guide clearance
  • Excessively worn bridged pivots or rocker arms
  • Excessively worn camshaft lobes
  • Faulty valve lifter check ball
  • Incorrect valve lifter(s)
  • Loose rocker arms
  • Missing valve lock(s)
  • Restrictions in valve lifter oil holes
  • Reversed rocker arm nut (installed up-side-down)
  • Worn valve lifter face(s)