The high-voltage ignition coils are secured directly to the spark plugs.
If the engine starts poorly, stalls or runs unevenly, the cause of these faults may be the spark plugs, even if they look perfect.
The choice of a correct and reliable spark plug determines the optimal operation of the engine during its use.
An important criterion when choosing a spark plug at the time of purchase is the heat range, which characterises the amount of heat that the spark plug can conduct through itself to the cylinder head (heat rating).
When the electrodes and insulator overheat, premature (glow) ignition occurs.
In other words, if the spark plug is too "hot", it will not be able to cool sufficiently before the next portion of the air-fuel mixture enters the cylinder.
As a result, glow ignition will occur — ignition of the mixture not from the spark, but from contact with the heated parts of the spark plug.
The heat rating of the chosen spark plug must strictly correspond to the value recommended for your engine.
Short-term use of spark plugs with a slightly higher heat rating is permitted, but it is categorically prohibited to use spark plugs with a lower value, as this can lead to the most severe consequences, up to blowing the cylinder head gasket, burning out the pistons, valves, etc.
If the spark plug is too "cold", carbon deposits will contaminate the electrodes and insulator of the spark plug.
This fault will cause the spark to leak along the insulator, from the centre electrode to the skirt of the spark plug insulator.
Such a fault leads to misfires, i.e. the air-fuel mixture does not ignite and, as a consequence, to uneven engine operation at idle, jerking and flat spots during acceleration, problems with starting the engine in winter and increased fuel consumption.
Long-term operation of the vehicle with systematic misfires and, consequently, incompletely burned air-fuel mixture leads to reduced engine power, increased fuel consumption, failure of the catalytic converter, reduced environmental safety of the vehicle, increased oxidation of the engine oil and damage to the vehicle transmission.
To carry out the task, a 10 or 8 mm socket and a special 16 mm spark plug spanner will be required.
We carry out the work on a cold engine.
We press the wiring connector retainer and disconnect the connector from the ignition coil.
We undo the ignition coil securing bolt.
On the F4R engine, the ignition coil of the fourth cylinder and the solenoid valve of the variable valve timing system are secured by a single bolt.
Before undoing the spark plugs, the spark plug wells must be blown with compressed air to remove dirt and dust from the spark plug wells.
We turn the solenoid valve of the variable valve timing system, freeing the coil flange.
We withdraw the ignition coils.
Using a spark plug spanner, we undo the spark plugs.
We withdraw the spark plugs from the spark plug well.
We examine the spark plugs and assess their condition.
We check the gap between the spark plug electrodes with a feeler gauge.
For the K4M engine, EYQUEM RFN58LZ, CHAMPION RYCLC87 spark plugs are used — gap 0.95±0.05 mm.
For the F4R engine, CHAMPION RC87YCL — gap 0.9±0.05 mm, NGK PFR6G-9 — gap 0.85±0.05 mm.
If the gap does not correspond, we bend the side electrode.
When installing the spark plugs, we first screw them in by hand (without a tommy bar), and then tighten them to a torque of 25—30 Nm.
Excessive tightening of the spark plugs can damage the thread in the spark plug openings of the cylinder head.
On the inner surface of the ignition coil terminals, we apply a special compound Fluostar 2L.
