im having a problem with my car. when u give it gas in idle it hesitates for a second then revs, but when i let off gas it continues to rev for a second, then drops back down to a idle. Also when i let off the gas it sounds like it back fires though the exhaust a lil and a few drops of dark liquid drops out of the exhaust pipe. the engine has about 150,000 miles on it. any tips or advice on how to fix it would be helpful thanks

 

Sounds like you have a couple of problems. The first thing I would do is run a vacuum test, then a compression. Unless you know what your doing your going to have to take it to a shop to get it diagnosed.