The tps switch ( throttle position switch ) is located on the throttle body ( carburator ) it is a small switch with two screws holding it on. you can look on napa, autozone sites to see picture of it. I just bought my 2002 ranger last week, and this started the other day with the revs. I did some research and found this was a problem with the rangers. The tps switch cost about $30 dollars. Make sure you really clean the plug with electrical cleaner spray. Im going to try this with mine. make sure you install the tps switch back in the exact same spot. not to hard to do.

Heath