Looks like your head gasket's about to go. You should take it to the repair shop on the moped so your engine doesn't blow up. Also, you might consider saving up somewhere between 7500 and 8000 so you can replace all the engine parts with new ones. Better safe than stranded.
As for reverse, maybe your transmission's messed up too.
It would be easier to see what's going on if you attached your save file in a reply. Assuming you're using windows, that's located under C:/Users/User/AppData/Amistech/MySummerCar/
It's a file called defaultES2File.txt
