Toyota is to recall 3.8m vehicles in the US – reportedly its largest ever recall in that market – to check for incorrectly installed or incorrect driver’s floor mats that could jam the accelerator pedal. The move followed the deaths of four people earlier this month in a new Lexus dealer demonstrator apparently fitted with the wrong mats.

“Recent events have prompted Toyota to take a closer look at the potential for an accelerator pedal to get stuck in the full open position due to an unsecured or incompatible driver’s floor mat. A stuck open accelerator pedal may result in very high vehicle speeds and make it difficult to stop the vehicle, which could cause a crash, serious injury or death,” Toyota Motor Sales USA said in a statement.

On 14 September, Toyota issued a statement responding to the 28 August death of California Highway Patrol officer Mark Saylor and three members of his family on a highway near San Diego, California, while driving a 2009 Lexus ES350 loaned to them by a local dealer.

The LA Times said that, before the crash, the driver called emergency services to report that the accelerator pedal was stuck and that the car was travelling at 120mph (200km/h). Investigators were trying to determine whether a floor mat played a role in the accident.

Toyota said then that “preliminary information from law enforcement investigators indicates that the cause may have been an all-weather floor mat from a different Lexus model which, if installed incorrectly in the ES350, could cause it to interfere with the accelerator pedal.”

“Driver’s floor mat interference with the accelerator pedal is possible in any vehicle make with any combination of floor mats when the floor mat is not properly secured or if it is not the factory designed floor mat for the vehicle.

It consequently advised dealers to “immediately inspect” all vehicles in their care and also urged “all other automakers, dealers, vehicle owners, and the independent service and car wash industries to assure that any floor mat, whether factory or aftermarket, is correct for the vehicle and properly installed and secured”.

Toyota said last night it would soon launch a recall but, as an interim measure, was asking owners of specific Toyota and Lexus models to take out any removable driver’s floor mat and not replace it with any other mat.

Affected models are the 2007-2010 Camry; 2005-2010 Avalon; 2004-2009 Prius; 2005-2010 Tacoma; 2007-2010 Tundra; 2007-2010 ES350 and 2006-2010 IS250 and IS350.

The automaker has also recommended a number of steps drivers can take should a loose floor mat cause the vehicle to accelerate.

Toyota told US media it had been receiving complaints from consumers about uncontrollable acceleration because of floor mat entrapment dating back to 2004 but was moved to act in part because of the San Diego accident and the publicity it had received.

“Obviously the tragic accident in San Diego was certainly an eye-opener for us,” spokesman Irv Miller said. “We’re trying to raise floor mat awareness.”

Toyota said it had been in discussions with the National Highway Traffic Safety Administration for the last week to 10 days on the matter and that it developed the current consumer advisory in consultation with the agency.

“This is an urgent matter,” said US Transportation Secretary Ray LaHood, who oversees the highway safety agency. “For everyone’s sake, we strongly urge owners of these vehicles to remove mats or other obstacles that could lead to unintended acceleration.”

The automaker told the LA Times it had engineers working on fixing the problem and, once resolved, would issue the recall notice to owners and cover any costs involved in repairs or the replacement of floor mats.

Auto safety researcher Sean Kane, founder of Safety Research & Strategies in Massachusetts, told the paper his group was reviewing more than 1,500 reports of unintended acceleration involving Toyota and Lexus vehicles since 2000. Although many of the incidents appeared related to the floor mats, Kane said, there may have been other causes, such as electronic control malfunctions.

“This is one of those issues that’s going to take some time to unfold,” added Kane.

Toyota is not alone with the problem. During the 1980s, Audi issued a series of recalls in the US involving unexpected acceleration problems in some of its cars though investigators concluded that in many cases, the problem was caused when the driver stepped on the wrong pedal.

In the last two years, Toyota has recalled more than 4m million vehicles worldwide because of problems with brakes, window controls, fuel systems, steering and seat belts.

In September 2007, Toyota US recalled ‘all-weather’ floor mats used in 2007 Lexus ES350 and Camry vehicles in response to complaints that they could slip forward and trap the accelerator pedal. That year, Consumer Reports magazine said it would no longer automatically give Toyota vehicles its coveted “recommended” stamp because of reliability problems, the LA Times noted.

Toyota’s suggested measures to stop the unintended acceleration include shifting the gear selector to neutral but some drivers have complained that neutral can be hard to find on some Lexus shifters especially during emergencies, Kane told the LA paper.

“Once these vehicles have an unintended acceleration episode, it can be extraordinarily difficult, if not impossible, to find a way to shut the car down,” he said.