Today my check engine light came on in my 86 toyota van while driving but then it went away. Later on I noticed that It came on again while I was driving when I hit the gas while running and got no power but then eventually the power caught up and resulted in a power surge. The van is running kinda roughy. Not too bad but the check engine light comes and goes. Where should I start? I checked the codes and got codes 4 and 11. I find the owners manual so I hope someone can look that up for me and give me some decent advice on what to do.