The disabled vehicle when delivered by flatbed car hauler unit to the nearest dealership, Petro Nissan, 47 miles from the breakdown site would not move at highway speed but only jerked/bucked and crept along at little more than a fast walk. This condition was last experienced when the vehicle had been on a remote undulating interstate for about 2 hours. The check engine light had reappeared after being recently reset and the engine revving and loss of ground speed started causally then increased in frequency and intensity until totally failing to the point of forcing me to creep with emergency flashers in mode on the shoulder to reach an exit two miles ahead. The high RPM revving coupled with the ground speed loss condition initial stages occurred each of the two prior days. Two Nissan NA dealerships in those two days had performed diagnostics and service. On each prior day the check engine light, the high revving engine RPM, and the ground speed loss occurred. On each day a potentially serious safety issue arose. Initially an attempt to match speed and merge with traffic at an onramp and again when (using cruise control) during which the vehicle system attempted an automatic acceleration to maintain speed on rolling hills. Both conditions forced me to the shoulder to avoid a potential accident from immediate and drastic ground speed loss and engine revving at or above 4500 RPM After each of these incidents a Nissan NA dealership was consulted and services were performed. In each case I postulated to the service advisors that the transmission sounded/felt like it was slipping on acceleration when the vehicle/ transmission had heated up from extended driving. Both days service advisors checked for diagnostic codes of transmission issues but never mentioned emission issues aside from mass air flow sensor or ABS sensors apparently either not seeing or not looking beyond transmission related codes. The first dealer, Illini Nissan, ran diagnostics on 1/6/25,