Toyota secretly bought back from US consumers vehicles it found with speed-control defects as part of a strategy to hide unintended-acceleration problems from safety regulators and the public, a revised lawsuit claims.The repurchase transactions included strict confidentiality agreements barring consumers from disclosing the problem to anyone and from suing the automaker, according to the amended class-action complaint.The new complaint also cites internal company records documenting instances in which Toyota technicians or service managers replicated speed-control problems like those reported by customers.And it says the company's confirmation of at least one clear-cut case of sudden unintended acceleration was concealed rather than reported to federal auto safety regulators.The enlarged lawsuit, now more than 700 pages long plus hundreds of pages of attached exhibits, was filed on Wednesday in a US District Court in Santa Ana, California, south of Los Angeles. It builds on a case consolidated over the summer from dozens of consumers and businesses claiming economic losses, including diminished vehicle resale values, stemming from complaints of Toyota cars and trucks racing out of control.The thrust of the lawsuit is the contention that Toyota ignored evidence of speed-control problems in its vehicles for most of the past decade and failed to install a brake override system it knew could have prevented accidents.Toyota acknowledged in a statement on Thursday that it has repurchased vehicles from customers who complained of unintended acceleration but did so to conduct "further engineering analysis" on the cars.However, the company said its technicians have never been able to replicate those "acceleration concerns nor found any related issues or conditions in these vehicles."Liability waiver or gag order?Toyota spokesman Brian Lyons said customers selling back their cars were asked - not required - to sign a "settlement agreement" that included a release from liability, but those documents contained no requirement of confidentiality. The lawsuit lacks any documentation of confidentiality agreements but plaintiffs' attorney Steve Berman said "the consumers told us" about them.Lyons added that the vehicles were bought back subject to state "lemon laws" and that in at least some cases the repurchases were requested by the company rather than by the consumer. He declined to say how many vehicles Toyota had repurchased or how much the automaker paid.Toyota has acknowledged just two defects as a root cause for its vehicles speeding out of control - ill-fitting floor mats and sticking accelerators. Both problems were addressed in safety recalls of 5.4-million US vehicles.The company says many unintended acceleration cases stem from driver error and has denied the existence of a hidden flaw in its electronic throttle system, as the lawsuit suggests.But the revised lawsuit challenges those contentions by pointing to some of the company's own communications, including those in which Toyota technicians said they had reproduced engine surges like those reported by consumers.In examples cited, the precise cause of unintended acceleration experienced during test drives remained unknown, but in a series of field reports from 2006-2010 involving Toyota Camrys technicians from Hong Kong confirmed unintended acceleration in cars they tested while ruling out faulty floor mats or accelerator pedals, the lawsuit said.Moreover, the acceleration glitches were duplicated without the vehicle's diagnostic equipment detecting a malfunction.In a separate 2009 case a service manager described in a company memo as "trustworthy and reliable" experienced an unexplained burst of acceleration while test-driving a Toyota Tacoma. The vehicle raced from 113 to 153km/h in seconds with "no pedal contact" from the driver. Floor mats were properly secured, according to the lawsuit.