Charles C. Roberts, Jr., Ph. D., P.E

Statements by an insured that the accelerator pedal stuck and caused an automobile accident are not unusual. Although many such claims are unfounded, some do, indeed, have technical merit. In one instance, an insured was driving a van when the accelerator pedal did not return to the closed throttle position. Repeated “jabs” to the pedal did not rectify the condition. The claimant then jumped from the vehicle, which, apparently, did not cause serious injury. The vehicle continued forward, starting to turn slowly in a circle, traveling over curbs and a vacant field. The serious injury to the claimant occurred when the vehicle circled back and ran over the claimant. Witnesses indicated that the vehicle was traveling about 20 mph - attesting to the theory that the vehicle throttle was at least partially open. The vehicle was inspected and disassembled in the presence of interested parties. During the inspection, it was noted that the throttle was about 1/3 open and did not return to the closed position. There were no obstructions that could have prevented the return, other than some problem in the throttle linkage system. The throttle body and throttle cable were removed for inspection.

Figure 1

Figure 1 is a close-up of the throttle bellcrank and throttle cable assembly. The right arrow is the throttle cable assembly.The left arrow is the bellcrank that operates the throttle plates, controlling engine speed. The throttle cable attachment point on the bell crank would not swivel as originally designed. Figure 2 is a view of the system with the throttle cable assembly removed.

Figure 2

In Figure 2 the left arrow points to the bell crank ball stud. The right arrow points to the cable attachment point. Severe corrosion was found in the ball joint cavity. Apparently, the ball stud corrosion did not allow free movement of the ball joint mechanism, resulting in the accelerator system not returning to the closed throttle condition. The corrosion induced failure mode of this system resulted in intermittent failure to return to the closed position. The stickiness of the accelerator could vary depending on time of year, corrosion rate and vehicle usage. The vehicle involved was about 6 years old. Typically, joints of this type are maintenance free for the life of the vehicle. In this case, there appeared to be either a manufacturing or design, corrosion-related, deficiency that caused premature accelerator linkage failure.