I recently took my 94 ford explorer into the shop to have the check engine light. The mechanic told me it was a fuel injector not fireing as suppost to. He asked me if it was running fine. I told him OK with the exception of it really knocks going up any hill. Could this be due to the injector not operating correctly? I have ran numerous injector cleaners through the gas. If I need to replace is this something I could do, (I feel I am pretty handy) or would you recomend to have it done at the shop? Thanks for your time. Pete