Here's the problem.

It may not be in the accelerator code. It could be someplace completely different.

It's likely a buffer overrun someplace else in the code.

Here's how it works.

Let's pretend you've got some code to warn that your turn signals are on too long. You set aside a variable to store the count of the clicks. You're short for space, so you use a variable type that only stores a maximum of 255. It's supposed to reset every time somebody turns off the turn signals. Somebody else decided the whole thing was a stupid idea and took out most of the code (including the reset) but forgot the counter. So now, every 255th' time you use your turn signals flash, a number of a larger data type gets put into this memory space, leaking into the memory allocation next door, changing that number in unexpected ways. It could be something simple like the area where the speed for the cruise control is stored, so it now decides it wants to go 200 instead of 70. It could be the register for "what do I do next?" so instead of checking the fuel-air mixture, it decides now would be a good idea to accelerate. It could be something like it only occurs if you're right turn signal has been used 256 times on a rainy day in a month ending in "y" and your radio station is tuned to a station whose digits add up to 11.

It could be any of the code anywhere in the system, reportedly millions of lines of code. Buffer ovsrruns are notoriously hard to spot.

Good luck finding it without a complete top-to-bottom code review.