Toyota Repair: check engine light on, pep boys, trouble code

Question
97 4-runner with rought idle,almost killing. Replace spark plugs and plug wires, then had Auto Zone clear check engine light. Few days later check engine light back on, vehicle runs fine. This is what I needed to know, what would be the most reasonable meter I may buy to do my on diagnotic and repair ? What every help you can give would be greatfull.

gtgrant  

Answer
Autozone, pep boys, and a few others sell a code reader for about $100 or less, they will tell you what the trouble code is, if you could have autozone check for the trouble code again and let me know what it is I may be able to help you without investing in the scanool. I can't help without knowing the trouble code.