I have a 1990 honda accord ex and the check engine light stays on, Also it takes 3 to 4 minutes to start the car.

Check your EGR valve... this happened to my Lumina last year and I couldn't get it inspected. A friend of ours cleaned it out and works great!

Perform tests in sections A and B below:

https://www.askmehelpdesk.com/cars-trucks/faq-how-troubleshoot-repair-maintain-honda-civics-46563.html

Be sure and run the K-Test on your ECM.