Cat delete

[Erich Zeppelin]

Thinking about getting rid of the two cats on my 1999 Expy. Any advice or recommendations? 5.4L with only two cats.

 

[toms89]

Pellet gun!? Big dog?! Hose?

Gotta hate paw prints!

 

[toms89]

Think many here have done rear cats delete with not issues or CEL's.

Can't really speak for performance differences as have not done myself.

 

[Erich Zeppelin]

Pellet gun!? Big dog?! Hose?

Gotta hate paw prints!

Good Lord, ten thousand comedians out of work and your trying to be funny.....

 

[Erich Zeppelin]

I've read all about the folks with four cats deleting the two rears, but I can't find anything about deleting the factory dual cats.

 

[IMINYOURCHAIR]

Pellet gun!? Big dog?! Hose?

Gotta hate paw prints!

God am I thick headed. had to read that a few times to understand it..


OP: any good reason you want to delete them?

 

[Erich Zeppelin]

Just trying to simplify my ride, plus I have P0240 code, replaced all 4 O2 sensors but after a few days the code was back......

 

[IMINYOURCHAIR]

does the exhaust sound like shit too perhaps? I had the same code on a previous car and it turned out the cat had been gutted and left in place. didn't find out till I had the "cat" cut out and asked to have the old part, only to receive a hollow chamber..

 

[CaperCanadian]

I have all the cats removed from mine, front 2 hollowed out and rear 2 removed. Has a nice low rumble now even with the factory muffler in place. No CEL with it yet and has been 5 years.

 

[Bowesmobile]

Just pop them out and move on. Keep the engine tuned and fresh there shouldn't be any extra pollution. I know people that have wicked modified cars without cats and still pass the Jersey sniffer year after year. They keep up on regular maintenance and everything is good.

 

[Erich Zeppelin]

What about the four O2 sensors? Will the engine run rich/lean and start to cause damage?

 

[BAD RONALD]

Just pop them out and move on. Keep the engine tuned and fresh there shouldn't be any extra pollution. I know people that have wicked modified cars without cats and still pass the Jersey sniffer year after year. They keep up on regular maintenance and everything is good.

This is good to know.

It would be great to hear confirmation from others passing emissions testing similarly.

 

[Bowesmobile]

If anything it will make the mixture more rich by a small amount and that will offset the extra flow giving you better gas mileage. I have done this time and again. Works every time.

I'm trying to remember the guys name in Jersey. He used to modify Merkurs. Bigger turbos and volvo head swaps, that were pushing 6-700 RWHP. But every year he would have to pass a emissions test like everyone else. Every year he would pass sometimes better than the parameters set for the vehicle.

 

[BAD RONALD]

Makes sense to me.

CT Emissions testing is pretty much a joke in my opinion anyway. A "$20 car tax" as my father used to call it. (Double it if you are past due). At present it appears they only scan for fault codes and check the gas cap seal. No sniffer used any more unless you show up with a pre-OBD system auto.

 

[toms89]

The 2 front O2 sensors are used by the pcm to tune the motor and are vital to its operation. The rear O2's are there only to monitor for the catalytic converters efficiency. Most do not have issues with only the two rear cats removed but with all 4 it should set off a cel if everything is functioning properly.

Some have done the 'anti fouler' mod with the rear O2's to move them out of the exhaust stream. The rear O2's can also be turned off in the tune but my guess is you will need custom tune to do so.

 

[Canadian Expy]

I put on a pair of magnaflow cats to replace all 4 no problems with codes or passing emission tests

 

[mr49erguy]

I have all the cats removed from mine, front 2 hollowed out and rear 2 removed. Has a nice low rumble now even with the factory muffler in place. No CEL with it yet and has been 5 years.

CaperCanadian - Have you seen an increase or decrease in fuel efficiency with the removal of the rear cats and the hollowing of the front cats?

 

[CaperCanadian]

Found a big difference with them gone, much better milage and noticed a difference in power and torque as well. I have noticed the last few months that I'm not getting the mpg I was before but discovered the o2 sensors are pegged out at 1 volt so they are shot. No shame for them, there is 225 thousand km on them. Also a question for the masses, are the back 2 real cats or resonators, I know you can't see through catalytic converters due to the packing in them but I could see through the hunny comb in my back ones clean through. Anyone who has the back ones out noticed this as well? .

 

[Big Red Monster]

take them F**KERS off if you have an exhaust like flowmaster that truck will sound so much better it rumbles like hell without the cats

 

[mr49erguy]

Found a big difference with them gone, much better milage and noticed a difference in power and torque as well. I have noticed the last few months that I'm not getting the mpg I was before but discovered the o2 sensors are pegged out at 1 volt so they are shot. No shame for them, there is 225 thousand km on them. Also a question for the masses, are the back 2 real cats or resonators, I know you can't see through catalytic converters due to the packing in them but I could see through the hunny comb in my back ones clean through. Anyone who has the back ones out noticed this as well? .

Thanks CaperCanadian. This confirms for me that I will be pulling my rear cats out eventually. I've only had my 98 Expy for a week now though. It sounds great as it is now, but if it can sound better and get better fuel efficiency and better torque that is a no brainer. Only issue here in Virginia is that I do have to adhere to emmissions standards. The rears are shot, I'm positive, but in order to go through inspection I cannot have them cut out. Many years ago I had a small vehicle with the cat hollowed out and re-welded back together very carefully. That was in Arizona though. Bottom-line, I just need to be careful. It makes no sense for me to have the rears in though. The muffler was replaced by the previous owner and it makes a great sound, but has a 3 inch pipe that narrows to the stock 2 inch exhaust pipe and looks a little funky, so at some point down the road I may have an exhaust shop do some rework from the rear cats back. Due to financial constraints that is a ways off though.

Phase 1 of repairs have been done as of yesterday and I feel good. Was able to get the front brakes redone. Drive side caliper was on wrong as it was for the passenger side. Brakes have been bled and they feel great now. PCV valve has been replaced and the throttle body has been removed and cleaned out and the plugs were inspected. They looked great, which blew me away. No fouling at all on them and I do not think they have been changed in over a year. The oil filter was moved by a previous owner to the driver side wheel well, which makes changing it MUCH easier and I'm happy about that. It also holds 6 quarts, which is cool with me. It does not look like the oil had been changed in a while, but the previous owner was not driving it very often. Because of this the battery (Duralast Gold) was not charged very well, but I charged it up for several hours while working on the rest of the vehicle and now she starts right up. I have a constant ABS light on the dash so we rechecked the brake fluid in the master cylinder, but it was fine as we had just bled the brakes. Ended up changing a $13 sensor in the differential, but that did not cause the ABS light to go out. More troubleshooting to come on that later. Lastly, I changed the rear window struts which were shot and now the window stays up on it's own when open. Overall a VERY productive day.