Spark Plug Malfunctions (General information / Help with malfunctions / Ford Mondeo 3 2000-2007)

Sign of recognition	Reason / features
A. The top of the thermal cone of the insulator is light gray to gray in color.	Spark plugs are mounted with a given glow number. Engine management (fuel mixture preparation, ignition system) works according to regulations, mechanical wear is within acceptable limits.
B. The top of the thermal cone of the insulator is whitish in color.	The insulator is overheated. bad (defective) fuel. Leaky valves. Too small valve clearance. The exhaust gas must be measured. Check engine management, possibly lean fuel mixture. In case of doubt, you risk major engine damage (piston seizure, piston burnout, exhaust valve combustion).
IN. The appearance of the screwed part of the candle is dark, the insulator is black.	The spark plugs are mounted with a high glow number. The candles are worn out. High share of short distance traffic. The air filter is closed. The motor control should be adjusted. The lambda sensor is not working properly. Exhaust gases are black.
G. The appearance of the screw part of the candle is black, the insulator is oily.	See B. high voltage ignition cable, spark plug plug defective. Oil scraper piston ring broken. Piston seizure. The valve stem gasket is worn. High oil consumption. Blue-black exhaust gas exhaust.

Spark Plug Malfunctions