The Vauxhall 1.8 has a major design fault - the ECU is bolted directly to the engine so suffers from vibration - this can affect the soldered connections of the ECU causing fatigue failure. Each of the sensors are cabled back to the ECU, including their earth circuits.
It's not uncommon for the MAF earth circuit joint at the ECU to fail - when this happens an auxilliary earth cable can be run from the MAF directly to earth but needs care as the cables at the MAF connector are very fine gauge.
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