The chocolate bars in acid were in the pilot episode. But he’s probably stopped leaks of dangerous substances multiple times, and it’d be kind of surprising if he never used chewing gum for it.
Qestion: is the track width of a Willis jeep equal to the width of a standard US rail line? From the same episode as the eggs-in-the-radiator.
This is the most questionable Macgyver move brought up so far.
I know it’s counter-intuitive but you’re gonna want to start with the wide end. 
Once while being chased by people who were trying to kill him, he stopped to rig the traffic lights to stop the people chasing him. Even IF the traffic could be configured (they couldn’t) was the bad guy’s thought, “sure I’ll kill Macgyver, but no way I’m running a red light”?
That’s the last episode I watched.
S1 E3 The bad guys were intelligence officers- they were in police vehicles, so they weren’t afraid of running red lights. He rigged the lights so they would all turn red, causing a traffic jam. That’s what stopped the officers in cars from keeping up, not red lights that they were afraid to run. The officers on motorcycles were able to weave through traffic and stay on his tail.