Volkswagen and Audi will recall more than half a million vehicles to replace a defective ignition coil that leaves the cars prone to sudden power losses and potential engine damage.

The action comes too late to soothe thousands of VW and Audi owners.

"The unreliability of the ignition problem and the lack of initiative by VW has killed any enthusiasm I have with the Passat," Paula of Horseheads, NY, wrote to recently.

"I am waiting to see if the coil breaks a 4th time before 28,000 miles," said Christopher of North Smithfield, RI, whose 2001 Passat has already burned through three defective coils.

Recalled models include 2001, 2002, and early production 2003 Volkswagen Golf/GTIs, Jettas, New Beetles, and Passats, and Audi A4s and TTs. All have 1.8-liter turbocharged engines. The companies also said the defect potentially affects the VW Passat W8 engine, all VWs equipped with the 2.8-liter VR6, and the Audi 3.0-liter V-6 engine.

VW would not call the move a recall and has insisted for months that the problem does not involve safety, though most VW and Audi owners would disagree.

The company's policy has been to replace only those coils that had failed -- leaving customers to drive away from their dealerships knowing that another coil could go bad at any minute. There is one coil for each cylinder, meaning that each car has at least four and as many as six coils, each one a potential source of trouble.

When a coil fails, it will drastically reduce a car's power. If the car is driven for an extended period with a bad coil, it could overheat the catalytic converter and cause serious engine damage.

Audi and VW have known about the problem for quite some time but did not want to call in all affected models because they did not have enough replacements available. The supplier has now manufactured a large number of replacement coils and letters will be going out to VW and Audio owners.

Those with questions can call VW customer relations at 800-822-8987 or Audi at 800-822-2834.

The coil problem has been a serious one for VW and Audi and the cost of the recall will be significant. Each coil is said to cost about $60, plus installation. If VW winds up paying about $300 to repair 500,000 cars, expenses could exceed $150 million.

The problem also comes at a bad time for VW, which is introducing several new models. Audi executives still have nightmares about their problems with allegations of unintended acceleration in Audis over a decade ago.