Most of the self-taught engineers that I've met struggle with algorithm questions, even relatively straightforward ones. Most also don't have a clear idea of things like algorithmic complexity and how to get an idea of how efficient an algorithm implementation would be. This is mainly because CS students are forced to learn this whereas self-taught programmers would need to be particularly motivated to sit down and teach themselves this, because there are no immediate practical uses for this.

The great debate of course is, how important are those skills? Many self-taught programmers I know reject the idea that these CS fundamental knowledge is important. And to their point, many self-taught programmers that I've met/hired/worked with that would be productive on day one because they have real-world knowledge and experience. Case in point, the founding engineer of the company that I work at is a college dropout, he's more than 15 years younger than me, and he's excellent. As well, I'm a self-taught programmer but came from a EE background, so I had two CS courses under my belt before I decided to pursue programming after graduating.