I have an ‘04 XJR with 150113 miles which keeps throwing a check engine light. The code is for an evap leak but I can’t find it. We smoke tested the car and no smoke came out. There was a slight hissing near the charcoal filter, but no smoke. Does anyone have any ideas of what could cause this? Or should I just replace the filter and pray?

 

Hissing is normally quite a big leak.

A typical small leak can't be heard, sadly.