2000 V6 Mustang 4 Cats to 2 Cats = Check Engine Light

[Stangman Jonathan]

As many know, we did the dual exhaust conversion on Janice's 2000 Mustang Convertible V6 over a year ago and she has been getting the check engine light on and off (whether or not this has caused it we are not sure). Never knew she originally had 4 cats and now only has 2 high flow cats with the pypes kit below:

http://www.americanmuscle.com/pypes-...ttedxpipe.html

The high flow cats were cut and put into place by a shop and have sounded very good but the check engine light is rather annoying.

She just had the check engine light checked again and turns out one of these cats is bad already?

Now my concern is whether there has to be specific placement for them (closer to the headers with 02 sensors in them) or (more towards the center of the car where the surface is flat like the cats). Her's plug into the rear 02 sensors not the fronts.

I spoke to a Magnaflow rep about getting replacements and he was the one who told me the car originally had 4 cats and that by having 2 closest up to the headers, we have a better chance of not causing the check engine light by the time the center sensors read it (after the cats).


I'm trying to figure out the best way for this to work since I will be doing the same thing with my F150s cat and just swapping them for 2 Magnaflows with 02 ports (debating putting them up higher near the headers plugged into the front 2 high flow sensors.




--- lots of writing but no other way to get my ideas out lol..appreciate your help. Thanks!

2 Upgrade Options: http://www.hottexhaust.com/detail.asp?Product_ID=51021
http://www.hottexhaust.com/detail.asp?Product_ID=51040

[Higu]

Interesting. Kristy went with duals and two cats and she has never had the check engine light come on for them. She's running Magnaflows too

[GT800]

Are you assuming they are are bad due to a catalyst efficencly low code? That doesnt mean the cat is bad hi flows sometimes tend to do that. Jon we spoke about what you would have to do to fix that the other morning.

[Stangman Jonathan]

Originally Posted by Higu

Interesting. Kristy went with duals and two cats and she has never had the check engine light come on for them. She's running Magnaflows too

Really? That's what we want to swap to. Any chance you can see if the front 02 sensors are plugged into them or if the rears are or if they are in between the sensors?

Originally Posted by GT800

Are you assuming they are are bad due to a catalyst efficencly low code? That doesnt mean the cat is bad hi flows sometimes tend to do that. Jon we spoke about what you would have to do to fix that the other morning.

Yeah I am not sure, just what she was told at the shop, one does have a pretty bad ding in it from when she went over a speed bump....hopefully you'll be able to see it next weekend.

I'm hoping it's just because of the high flows but at the same based on Higu saying her's is running just 2 without a check engine light and that they are magnaflows makes me want to try them in hers since they may just not throw a code?

Very true, don't remember all of it but will try to so i can remember to do that to mine.

[hpwrestler220]

I have 2 high flow cats and no problem...

I mean they were on the car when i got it but still.

Aren't you supposed to plug the 02's into the front cat's by the headers and then use MIL's or a tuner to turn off the rear 02 sensors...? But you're saying her cats are the ones that are futher back from the header? That's weird. Idk much about this

[MustangSally86]

This is a pic of the dent in my cat on the passenger side.



As you can see my o2 sensor plugs right into my cats.

When I brought it to Reyco, Ray informed me that one of my cats was coming up bad, but my air flow was not being restricted. I have replaced all of my o2 sensors already this year.

Sorry the pics are not the greatest

[Stangman Jonathan]

so what do you guys think? The kit from pypes says for them to be cut and put in place there.

Originally Posted by hpwrestler220

I have 2 high flow cats and no problem...

I mean they were on the car when i got it but still.

Aren't you supposed to plug the 02's into the front cat's by the headers and then use MIL's or a tuner to turn off the rear 02 sensors...? But you're saying her cats are the ones that are futher back from the header? That's weird. Idk much about this

Funny thing that's what I thought but pypes designed this kit oddly and we never questioned it thinking it was something else causing the check engine light.

[fredjbradford]

For what its worth, my 91 GT came with four cats. Since then I have BBK shorty headers, BBK h-pipe w/ high flow cats & new ford sensors mounted down stream. No engine lights & this mustang has always passed emissions. Good luck with your homework. Keep us posted!

[Hotshot]

Well my $.02 is that the only O2 sensors that matter are the forward of the cat ones as they read your AFR and make changes to your timing and such. The O2 sensors behind the cats only real purpose is to read if the cat is good or not.

If you placed the sensors too close to the headers, you may be exposing them to too much heat for them to handle.

And what is the specific code the car is throwing btw?