Finally passed my IEM exam last week after 8 weeks of studying. I was putting in about 90 minutes a day on weeknights and longer sessions on Saturdays. Scored 74% on my first practice test and got it up to 83% by test day, which turned out to be enough.
The AC/DC motor controls section was the part I kept getting wrong early on. Specifically the ladder logic diagrams and PLC troubleshooting scenarios - they're not intuitive if you've been doing mostly relay-based work in the field. I'd say that section alone accounted for about 20% of the exam.
Power factor correction and harmonic distortion questions also showed up more than I anticipated. The math isn't hard but the way the problems are worded can trip you up if you're reading too fast. I made a lot of silly errors on those until I slowed down.
What helped most was finding real troubleshooting scenarios online and walking through them step by step. Reading NEC articles related to industrial installations also filled in gaps I didn't know I had.
Passed mine with 78% after 10 weeks. The NEC industrial sections caught me off guard - I'd focused too much on the theoretical and not enough on code compliance questions.
The motor controls section is no joke. I'd strongly recommend going through real wiring diagrams if you can find them, not just textbook examples. The exam uses real-world scenarios.
PLC ladder logic was the hardest part for me too. I spent an extra 2 weeks just on that section and it was worth it - probably 6 or 7 questions on my actual exam came from PLC diagnostics alone.
Did anyone else think the harmonic distortion math was harder than it looked? I got those problems right in practice but blanked on two of them during the actual exam.
Failed my first attempt back in March and honestly electrical systems/circuit analysis was what got me. I thought I understood it but the actual test questions were way more application-based than I expected. What I changed the second time was grinding free iem electrical systems circuit analysis practice questions specifically until I could do them without hesitating. It's a different skill than just reading the material.
The other thing I'd say is don't skip AC/DC motor controls even if it feels tedious. I underestimated it both times honestly, but the second time I at least knew what to expect so I could manage my time better. You've got this if you're already putting in the hours.