General Motors Corp. says it has found no mechanical cause of sudden acceleration in its C-body and H-body cars and says the federal investigations of complaints don't mean a defect exists.

The automaker made the statement after the National Highway Traffic Safety Administration said Tuesday it had opened an engineering evaluation of 1.4 million 1985-88 C-body cars, including the Oldsmobile 98, Buick Electra and Cadillac Deville and Fleetwood.

The agency last year began an investigation of 703,000 GM H-body cars, including the 1986-87 Oldsmobile Delta 88 and Buick LeSabre, and the 1987 Pontiac Bonneville.