when they quit working i'd say....
i still have my originals at 128K
but if you do replace them....i suggest only replacing them w/ the ford replacements...i had bosch in mine for a couple thousand miles, and i didn't run quite as strong, i got worse mileage, etc....
i put the original ones back in and it ran great again...go figure...
I agree with Quick01snake on the OE parts. However, I got a set of Bosch O2's for my '96 and when I took them oit of the box, they had the Ford logos and part numbers stamped on them. They were abour $20 less than from the dealer. So I would say shop around. Again, "go figure".
ok, so is it a good idea to clean them once in a while with electrical cleaner?
for some reason its just doesn "feel" as fast as before... it could be in my head, or it could have something to do with all the suspension mods, I dont have the traction issues that comes with wheelhop anymore.