My wife has a 2001 Blazer 4.3. When I drive it to work about 11 miles I have no problems. When she takes it to work which is about a 35 mile trip. She said she gets about 20 to 25 miles or so into her drive on the highway running about 55mph and it will start slowing down and gets down to about 25 mph no matter how much she presses on the gas. Then it will start running back up to speed. She said when it starts to drop in speed the tach jumps back and forth between 1000 and 2000 rpm.

Does this sound like a bad catalytic converter? If so is there a way to check for a bad catalytic converter?

What has me puzzled is the jumping back and forth on the rpms.

I asked her if she smelled anything like rotten eggs and she said she hadn't noticed any smell but said she thought the floor board felt kind of warm. Any help is greatly appreciated.

Dave