WORKERS at one of Europe's biggest and most advanced car plants are secretly planting wrong and faulty parts onto the assembly line...and management know it's going on.

But this is not industrial sabotage - it's all part of a sophisticated quality control system designed to spot problems before cars reach the end of the production line.

To make sure faults are spotted, employees at Ford's Valencia plant have been tasked with secretly planting "gremlins" into the assembly process, including incomplete steering wheels and faulty engine components.

It's all designed to test Ford's industry-first Vision System which photographs, checks and tracks every single part of each of the 400,000 cars and vans assembled as well as the 330,000 engines built at the plant each year.

"Gremlin Tests" are an innovative way of ensuring that each process is working correctly, says the company. Faulty engine parts, wrong steering wheels, and even incorrect dashboards have been sent down the line, with the tests covering all 34 stages of assembly.

Technical specialist Xabier Garciandia's working day involves literally trying to put a spanner into the works by making sure wrong parts and faulty components are secretly placed on the assembly line.

"The Vision System is crucial to ensuring every single part of each vehicle is just right," says Garciandia. "It is a game with a very serious point; we are making them harder to spot all the time."

The Vision System captures more than a billion photos every 14 days and helps to generate a composite image - consisting of 3,150 digital photographs - that highlights any discrepancies to engineers on the spot.

Ford produces more Ford models at the state-of-the-art, mega-plant in Valencia than anywhere else in Europe, including the Kuga, Kuga Vignale, Mondeo, Mondeo Vignale, Galaxy, S-MAX and Transit Connect and Tourneo Connect vans. Ford's two-litre and 2.3-litre Ecoboost engines are also built at the plant.