Check the engine oil level or condition. If needed, refill or replace the oil.

Check the engine oil level within normal engine operating temperature as follows ;

When checking engine oil level or condition, if needed, change the engine oil (including the oil filter) as follows ;

After checking the accessory drive belt for looseness, crack, wear or tension, replace the belt if necessary.

A - New belt

B - Moderately used belt : few cracks, some wear on ribs and in grooves. Replace is not required.

C - Severely used belt : several cracks per 30 mm. Should be replaced before chunking occurs.

D - Failed belt : separation of rib material from the backing (chunking). Replace belt immediately.

After checking the spark plug for bad clearance, excessive carbon deposit, worn electrode or damaged insulator, replace the new one if necessary.

Remove and check the spark plug as follows ;

A spark plug can perform poorly due to wear, dirt, carbon fouling, excessive electrode wear, a broken insulator or excessive gap.

Worn or dirty plugs can give satisfactory operation while the vehicle is idling, but break down under load.This can cause :

Carbon fouling is indicated by black carbon deposits. The black deposits are usually the result of slow-speed driving and short runs. In these circumstances, the optimum engine operating temperature is seldom reached.Fouling can also be caused by :

This often indicates :

Broken insulators are usually the result of improper installation or carelessness.

Breaks in the upper insulator can result from a poor fitting spark plug socket or impact. The cracked insulator may not show up until oil or moisture penetrates the crack. The crack is often just below the crimped part of the shell and may not be visible.

Breaks in the lower insulator often result from careless re-gapping and are usually visible.

This can also result from the plug operating too hot. For example, in periods of high speed operation or under heavy loads.

a - Normal : Brown or grayish-tan deposits and slight electrode wear indicate correct spark plug heat range and mixed periods of high and low speed driving.

b - Carbon Fouled : Dry, fluffy black carbon deposits possibly due to poor ignition output, a weak coil, excessive idling or slow speeds under light load. If spark plug temperatures remain too low for normal combustion, the deposits are not burned off.

c - Oil Fouled : Wet, oily deposits with minor electrode wear possibly due to oil leaking past worn piston rings. Breaking in a new or recently overhauled engine before the rings are fully seated may also result in this condition.

d - Deposit Fouling A : Red brown, yellow and white colored coatings on the insulator tip which are by-products of combustion. They come from fuel and lubricating oil which generally contain additives. Most powdery deposits have no adverse effect on spark plug operation, however, they may cause intermittent missing under severe operating conditions.

e - Deposit Fouling B : Deposits similar to those identified in deposit fouling A (4). These are also by-products of combustion from fuel and lubricating oil. Excessive valve stem clearances and / or defective intake valve seals allow too much oil to enter the combustion chamber. The deposits will accumulate on the portion of the spark plug that projects into the chamber and will be heaviest on the side facing the intake valve. If this condition is only detected in one or two cylinders, check the valve stem seals.

f - Deposit Fouling C : Most powdery deposits identified in deposit fouling A (4) have no adverse effect on the operation of the spark plug as long as they remain powdery. Under certain conditions of operation however, these deposits melt and form a shiny glaze coating on the insulator. When hot, this acts as a good electrical conductor allowing the current to flow along the deposit instead of sparking across the gap.

g - Detonation : Commonly referred to as engine knock or pinging, detonation causes severe shocks inside the combustion chamber causing damage to parts.

h - Pre-ignition : Burnt or blistered insulator tip and badly eroded electrodes probably due to the excessive heat. This is often caused by a cooling system blockage, sticking valves, improperly installed spark plugs or plugs that are the wrong heat rating (too hot). Sustained high speed with a heavy load can produce temperatures high enough to cause pre-ignition.

i - Heat Shock Failure : A rapid increase in spark plug tip temperature under severe operating conditions can cause heat shock and result in fractured insulators. This is a common cause of broken and cracked insulator tips.

j - Insufficient Installation Torque : Poor contact between the spark plug and the cylinder head seat. The lack of proper heat transfer that results from poor seat contact causes overheating of the spark plug. In many cases, severe damage occurs. Dirty threads in the cylinder head can cause the plug to seize before it is seated. Ensure the cylinder head and spark plug threads are free of deposits, burrs and scale before installation.

If the air cleaner element becomes dirty, engine efficiency could be deteriorated. Be sure to check the element often and replace a new one within the specified period. Especially, if a vehicle frequently runs on a dusty road, check and replace the element often.

Check the fuel system as follows ;

Check the engine vacuum hoses, PCV hose or canister hose as follows ;

The V6 engine features a closed vee, deep skirt die cast aluminium cylinder block with cast iron cylinder liners, internally balanced crankcase, full length water jackets and six bolt main bearing caps.

The cylinders are arranged in two banks of three with a 60 degree included angle between the two banks. The rear bank of cylinders consists of number 1-3-5 cylinders (BANK 1) and the front bank of cylinders consists of number 2-4-6 (BANK 2).

The engine firing order is 1-2-3-4-5-6. Each aluminium cylinder head is fitted with hardened valve seats and four valves per cylinder: two intake and two exhaust. The valves are operated by two camshafts (DOHC) per cylinder bank, one each for intake and exhaust valves. Variable camshaft timing is provided via four actuators fitted at the front of each camshaft.

The crankshaft is manufactured from forged steel. A reluctor wheel is pressed in place onto the rear of the crankshaft for the crankshaft position sensor.The connecting rods are manufactured from powdered metal and the rod cap is separated during the manufacturing process using the fractured method. This creates a stronger, visually seamless rod to cap union.

An automobile engine is a combination of many machined, honed, polished and lapped surfaces with tolerances that are measured in thousandths of a millimeter. When any material engine parts are serviced, care and cleanliness are important. A liberal coating of engine oil should be applied to friction areas during assembly, to protect and lubricate the surfaces on initial operation. Proper cleaning and protection of machined surfaces and friction areas is part of the repair procedure. This is considered standard shop practice even if not specifically stated.

Whenever valve train components are removed for service, they should be kept in order. They should be installed in the same locations and within the same mating surfaces, as when they were removed. Battery cables should be disconnected before any major work is performed on the engine. Failure to disconnect cables may result in damage to wire harness or other electrical parts.