Volkswagen, one of the most popular manufacturers in the Australian market, is facing growing pressure to tackle problems with its cars that have led to overseas recalls.

A coroner this week investigated the death of Ms Ryan, who was killed when a prime mover with two trailers hit her Golf from behind. The truck driver and Ms Ryan's family believe her car dramatically and inexplicably slowed before the crash. After Fairfax's reporting of the coronial inquest, 15 owners of Volkswagens have spoken of frightening experiences when their cars, including Golf, Passat, Polo and Eos models, suddenly lost power on highways and, in one case, a train line.

"I did not feel safe driving a car like that. It was frightening," said Jean Lim, who was driving a 2007 Golf automatic that suddenly decelerated. VW replaced the gearbox but the issue returned. Another driver, who owned a 2008 Golf automatic, said she drove "in constant terror". "The light comes up, the car just dies and you just pray that you're not smashed into," said the driver, who declined to be named.

Fairfax can also confirm the federal Department of Infrastructure and Transport is investigating Ms Ryan's death. It is "liaising closely with Volkswagen Australia", spokesman Craig Stone said.

The coroner, whose decision is due in late July, will assess whether Ms Ryan's death was due to fault on the part of the truck driver, her own fault, vehicle malfunction or a combination of factors. Her car was a manual; most problems overseas with sudden deceleration in Volkswagens are found in automatics.

Volkswagen's expert witness Warren Chilvers told the inquiry the vehicle information showed no evidence to suggest the car was at fault. The truck driver, Ivan Mumford, insisted he never saw Ms Ryan's brake lights come on before the crash, but he had seen them working earlier. Fairfax is not suggesting Ms Ryan’s death is linked to a fault in her car.  Volkswagen has this year issued recalls for almost 400,000 of its cars in China and 91,000 in Japan for problems with the high-tech automatic direct shift gearbox (DSG). The DSG problems have been connected to sudden power loss.

In the US, the company issued two minor recalls related to the DSG. Then, after a federal government investigation and bad publicity,  in 2009 Volkswagen launched a service program that repaired or replaced the transmission components of about 43,000 Volkswagens and 10,300 Audis at no charge.

But the company has resisted calls – mostly made in online forums and in comments replying to motoring articles – to issue a recall in Australia. Volkswagen executive vice-president Ulrich Hackenberg said  this month that the China recall related to a problem with Chinese-built DSGs. He said DSGs in Australia were made in Europe. But the company had not revealed where the faulty Japanese DSGs were made.

Volkswagen  currently has a "campaign" – which is like a recall but driven by the manufacturer – to fix an injector problem with some diesel models. But online forums have pointed out Volkswagen has no way of getting in touch with owners who buy the cars secondhand.

David and Norma Levin  had their 2007 diesel Golf booked in for the campaign service a week after  they suffered sudden deceleration while driving to Adelaide recently. They blame the injector fault for the incident. But Volkswagen says the campaign is not about a safety problem. Volkswagen Australia declined to answer a dozen  specific questions put to it by Fairfax Media about recalls and sudden deceleration.

But spokesman Kurt McGuiness said there were no plans for recalls. "Volkswagen conducts vehicle recalls in conjunction with the relevant federal government bodies. At this time we do not plan to announce a recall. Any recalls are conducted in accordance with the Consumer Product Safety Recall Guidelines issued by the Australian Competition and Consumer Commission."

Mr McGuiness said service campaigns are "deemed to be non-safety related in accordance with federal regulations" and are carried out within dealerships when vehicles are brought in for routine services.

The "limp home mode" – where a car reduces speed to protect the engine from extensive damage in the event of an issue arising – was not unique to Volkswagen, he said.

"Rapid deceleration is not an issue widely observed or reported with any Volkswagen vehicles ... However, should any of our customers have cause for concern with their Volkswagen vehicle, we urge them to contact our customer care team .. We are dedicated to rectify any lost confidence our customers may have in our products."

Mechanic Dean Coutts, owner and manager of Volkspower, a Volkswagen specialist, said sudden deceleration was not a problem he had seen.  "Yes we have customers who have their car go into limp mode, but that’s no different to any other manufacturer on the planet."

Fairfax also received complaints about sudden speed loss in a Ford Mondeo and a Mercedes ML 350.