Catalytic Converter Removal

[willycj]

Had my jeep for about 5 months and was replacing the exhaust hangers and noticed the cat had been removed. I'm not expecting prius fuel economy but i drove it about 100 miles last week and burned 12 gallons of gas. I know this a 30+ year old vehicle but could the cat removal have contributed to this?

 

[mtnwhlr]

Not having a cat is not going to hurt your gas mileage. You may need to give it a complet tuneup.

 

[Les]

Actually, removing the old catalytic converter tends to help the mileage in a lot of cases, but it doesn't cause it to go down.

 

[willycj]

I know it removes back pressure which is a good thing, but i have done to a previous vehicle with a sensor attached to the cat and the mileage went straight to hell. Would there have been a sensor attached to on the 1980 model? and if so, would disconnecting it make the mileage go down?

 

[Les]

Back when they first started putting catalytic converters on cars, they didn't have any sensors in them, so it's fine to remove it. You are correct though, that vehicles produced a few years later have sensors installed that feed info to the ECM, and removing a catalytic converter from one of those will freak out the computer and thereby adversely effect the way the engine runs. And FYI, CJ's didn't start having computers installed in them til '83 I'm fairly certain.

As for the mileage issue, I had the same problem on my '86, so I installed a low restriction air cleaner, removed the catalytic converter and put on a low restriction muffler. I also put in a high output coil, better wires, plugs, etc., and installed a Motorcraft 2150 carb. With all my improvements, I'm getting something like 14-15mpg and much better power.

 

[PaRenegade]

I removed mine after about 5 or 6 months of it's birth and don't remember having any issues with a drop in mileage. All it had was a tube that went back to the header I believe. Les is correct, computers were 83 and newer, but I believe some California versions may have had them in 1982 as a test run.