'94 Gt W/old Cats

[imp]

Finally got around to getting under this thing today. Found it has 4 cats, 2 small ones upstream, two twice the size downstream, 2 big mufflers after that. Mufflers marked "Ford", cats unmarked. Thinking about replacing the cats as a possible help for very poor fuel economy (5.0 .308 axle, T-5) of 12 to 14 mpg rural driving, 162K on the car. My '93 Cobra always did 20 mpg, easily, more on interstates.

Would it be worthwhile to poke a hole upstream of front cat, try measuring back pressure? Is there an easier way? What would back pressure at idle with a new cat be, anyway? I tried the super-expensive "cat cleaner" on my '04 Explorer 4.0L, with absolutely no change determined in any form, 160K original cats. Should original cats have some kind of identifier on them? Maybe they are already replacements.

Thanks for ideas! imp

 

[jrichker]

To find clogged catalytic converters or restrictions in the exhaust system, use an old fashioned vacuum gauge.

Vacuum gauge indications:

 

[95BlueStallion]

If you dont have to pass emissions testing, you could buy an off road H pipe and see if it wakes up the car. That woukd be cheaper than replacing all the cats on the stock pipe. It'll be quite a bit louder depending on your mufflers, though. Or a replacement catted pipe will be $500+-, but should also help your performance over the stock pipe.