The car was make a loud whistle so I changed the PCV valve and the whistle went away and now it doesnt shift properly. What would cause this?
You will need to be more specific on what the shifting is doing and if the transmission is automatic or manual. Also if check engine light is on then have the computer tested for codes and have the codes diagnosed to see if you may have knocked something loose or did not get the intake hose back on correctly. If the problem did not start until after you worked on it then go back over every where you worked and look for loose or broken components, connectors or vacuum hoses. If after all these checks still cannot find issue then seek professional help like a mechanic from YourMechanic.
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