Yes, it’s possible. If your basics are clear 4 months of preparation is more than enough to score 90 percentile in CAT.
While preparing, stay motivated and don’t let the zeal fade away.
Yes, with a well-planned preparation, you can score 90 percentile or above in CAT with 4 months of preparation. If your concept is clear, it will be easy to score 90+ in CAT with 4 months of preparation. However, if you are starting from scratch, then it may not be enough time.
Also, scoring only a high overall percentile in CAT will not be enough to be shortlisted for admission at reputed IIMs. You will need high sectional scores as well as a high overall percentile to be shortlisted. Besides different IIMs have different admission policies. You will need to improve your overall profile along with your score to get admission.