If the exhaust shop has time today im going to be taking it in today and getting my rear two cats removed, I have the front two removed. My question is will I have to do anything so I don't get cels? My truck is a 04 with custom true dual exhaust, its been custom tuned so the rear cats has been turned off. Any help would be great thanks

 

I do the gotts 02 mod. Basically you buy some spark non foulers and you double stack them. I have no cats and no tune for having no cats, however I have never had a MIL for them either.

Gotts Mod -> https://www.f150online.com/forums/ex...-mod-pics.html

 

The best way is to tune it. Your fuel mixture will be better with a proper tune.

 

Actually this is wrong. The computer uses the front 02 sensors for A/F and the gotts mod only affects the rear 02 sensors. The rear sensors job is only to tell the computer if the cat is working, and has zero affect on A/F.... You are basically allowing the rear sensor to take a small sample of air, this way it thinks the cat is doing its job and no MIL. The front 02 sensors are before the cats and the computer looks for a rich/lean switch from those.

 

^ These o2 sensors are NOT very accurate. They only tell the computer is it is rich or lean if the ratio gets out of the "happy zone". The computer doesn't actually make precise adjustments if the o2 sensors are reading in the "happy zone". This is why if you run a CAI intake on an 04-08 your engine will run too lean. The o2 sensors do not compensate for the increase air intake. This is the same situation in deleting your cats. When you delete your cats, your EGTs are higher due to the fact that there are no cats absorbing the heat. The exhaust velocity is also increased by a better flow path without cats. Both of these actions result in a leaner mixture, but still in the "happy zone" for the o2 sensors. Now, if you want your ration to be more accurate, then tune for the cat removal.

That being said, the o2 sensors on the new 5.0L engine are that accurate. They read down to the ten thousandths, and it's computer does make precise adjustments to these readings. This is why it is such and efficient engine.

 

If you have a SCT device as a programmer for your custom tunes it can be used to turn off your rear o2s.....

 

Will you still pass inspection with the rear o2's off?

 

^ You can leave them in while they are turned off. If you have a pair of these with the o2s behind them and a tune with the o2s shut off, you would pass every time. Unless they do a sniff test of coarse.

 

I have P0430 on now... truck is going in Monday for TB cleaning and Plugs. I told them about my cat work and the code and they are going to take a look for me. He said I was right with the info I was giving him about possible leaks and what not, so if it checks out ok... I'll get my custom tune done asap. I have a revised 87 custom Bill fixed for me, but I run the 93 canned now. I'll have to data log for him quick, since inspection in in February for me.

 

I don't have emissions test here in arkansas