Don't really know, does it stink ??, or is it all full of cigarette smoke ??, or stained by something ??... just curious... maybe a mild bleach & water solution & a scrubby sponge ??, lots of elbow grease, you need to protect the rest of the interior while trying to clean it thou... I did that once on a 70 Demon I had a long time ago, with white interior & white head liner, worked pretty well, I ended up taking the black carpet & white seats out so I wouldn't ruin everything, covered everything else & taped it off really good, trying to clean the headliner was that full of cigarette smoke stains, from a 60 y/o chain smoker that had the car before me, it was freaken discusting...