95 F250 5.8 Removed guts from cat converter - I know its illegal. Forum said that with O2 sensor in front of it - should be O K. Well I get about 5 mpg and now running much hotter in temp. I did this to improve gas mileage but cut it in half. I assume its running much richer and reading cold. I do have another cat to install if all else fails. Another post said you must have O2 sensor with EFI. Any ideas?

 

Pull the codes, something isn't right. Removing a cat will not kill mpg or cause it to run hot. Coolant temp sensor is a possibility. You didn't remove your O2 sensor did you? That has an effect on fueling.

 

What he ^^^ said. Cause yes, you can't remove the O2 sensor and expect proper operation.

The only other possibility is that you're running colder without the cat AND your thermostat is stuck open. That'll keep you fat-rich and you'll start ruining your cylinder walls pretty quick with all the extra fuel washing the cylinder walls down.

 

O2 sensor is still there. How do I tell if it is functioning? Will look for temp sensor this afternoon.

 

Pull the codes. Throwing parts at it is guaranteed to make you frustrated and broke.

 

just throwing it out there but did you really think stating that you commited a federal offense was a good idea. you realize you cant delete the statement ever and it will be on the internet that the fbi and cia hire people to monitor 24/7. forever

 

not trying to be hypocritcial or anything just throwing it out there

 

I think they have better things to do than to sit on a truck forum monitoring exhast threads.

 

While true, he does make a valid point. It's best not to blatantly admit such things on-line. Much better to discuss your friends truck.

Back on topic, pull codes first. As to checking the health of the O2 sensor, you can't do it with a cheapie DVOM since the signal "ping-pongs" back and fourth too rapidly.