White/Gray Smoke: Causes and Solutions

Ibiza, mileage 331,000 km, with a small but noticeable white/gray smoke cloud after starting!

'Since the mileage reached 317,000 km, I've been having problems with the fuel injection pump, likely due to a faulty fuel pressure regulator. After that, the fuel quantity control stuck, which is why I completely replaced the pump! The timing belt was also replaced at the same time.'

Since then, I've been investigating the smoking issue and suspected a defect in the cylinder head due to excessive peak pressures caused by an incorrect injection timing (faulty fuel injection control). The cylinder head gasket was replaced, and the head was inspected, but nothing unusual was found. The vehicle starts perfectly, and there is no noticeable loss of power or coolant. The valve timing and injection start are correct and have not changed since. The injectors are less than 40,000 km old and have been checked, with optimal pressure readings of 190 bar.

What else could be causing this smoke? I'm unfortunately at a loss! Yesterday, I rechecked the fuel injection quantity using VAG com. It shows 7.6mg during a cold start, which decreases to 6.8mg within 3 minutes. Does anyone have comparable values for the AFN engine? Or do you think this could be the cause? This value seems incredibly high to me! The RSW (resting state voltage) is at 0.720V.

Disconnect the vacuum hose from the throttle body and temporarily plug it. Then see if it's still smoking. White/gray smoke indicates unburnt fuel. Could it be the air filter? Or is there a vacuum leak due to porous hoses?