After Dr. Yost rigged the exhaust in Rockford's rental car causing Rockford to nearly lose consciousness while driving, Rockford jumped out of the car just before it went off the cliff. However, the Lincoln Continental he jumped out of was a recent (1970s) model. The car that flew off the cliff and exploded in the next scene, while the same make/model/color, was clearly an early 1960s model.
The phone number Jim provides at the hospital (555-8180) is not the same phone number (555-2368) seen during the opening credit sequence of every episode.
At the intersection where the accident occurred, a stop sign is visible on a low, fat wooden post. In the hospital, when Jim fills out and signs the accident report, he states there was "no stop sign".
Just before Jim is rear-ended, his window is open. Moments later, when the police see him, the window is up and cracked and his head is resting against it.
Rocky's truck is struck from behind, but after the accident Rocky tells Jim bricks went through the cab as a result of the accident. A vehicle hit from behind would not cause the bricks to go forward, toward the cab. After an impact from behind, the bricks would tend to move backward with respect to the Rocky's truck. This is an example of Newton's First Law of Motion. If Rocky's truck were hit from the front, then the bricks would have moved toward the cab.
When Jim is in the hospital, he is confronted by the two guys from the truck that hit him. Both men are handcuffed to each other as if they are both being arrested. While the driver would have been detained for driving while drunk, the passenger would not, since he had done nothing illegal. The police would have no legal cause to hold the passenger. Note: it's possible the passenger had given the officer trouble (off-screen) and he was being arrested for disorderly conduct, if not drunk and disorderly.
In the hospital, Rocky tells Jim that when the other truck rear-ended him, a cement block went through the cab and damaged the passenger side window. But when the accident was shown, none of this had happened. This shows that the hospital scene was filmed before the crash scene and that they didn't go back to re-shoot the hospital scene to correct it.
Lt. Becker tells Rockford that the plastic flex pipe was found after Rockford's rental car cooled off after the accident. The plastic flex pipe would have burned in the fire. Also, the flex pipe was connected to a hot exhaust pipe and had hot exhaust inside it. The flex pipe would have melted or burned, creating a hole for the exhaust to escape before Rockford loses consciousness.
Jim's truck was propelled straight forward and rolled to a stop. The cement blocks coming through the rear window (if that were possible) could not have turned right on all on their own and damaged the passenger side window.
In the accident, when Jim is rear-ended, his truck is propelled forward by the yellow truck. There is no-one in the driver's seat of Jim's truck when this happens.
When Rocky's truck is hit, just after the shock, the tire they used to protect the truck is visible, lying under the bumper. Nevertheless, it must have been quite a shock, as the entire bed of the truck moved.
When Jim is driving the Lincoln with the tampered exhaust, he gives no indication that there is something wrong with the car. However, car exhaust, especially from the inefficient, over-sized cars of that period, would have had a very strong odor. Jim would have known something was wrong long before he started to pass out.
When Jim meets Sorel at his office she refers to him as, Mister Yost and not Doctor Yost. As his secretary, she should know he is a doctor.
After the accident, Jim is seen slumped against the side window, which is broken from a large impact. Since the truck was propelled straight forward in the accident, his head would not have hit a side window, let alone with enough force to cause the amount of damage shown. In a rear-end collision, his head and body would have moved straight back, to the rear, not sideways.