When I have my car sitting at an idle, after about 10-20 seconds of idle it starts to drop below 1k RPMs and my car starts to do a weird knocking. Will disconnecting my negative terminal reset my idle? When I replaced my exhaust the other day I did manage to find a good bit of water in the old exhaust. The car has been sitting for a year with only a few starts in that time.

 

Clean the IACV and then adjust the idle speed (see FAQs sticky).

 

the gas will also need to be replaced.