I replaced all 4 02 sensors on my truck with AC Delco's and was still getting the P0420 code. One of the new sensors had shorted out. Replaced it and no more code. Could be something that simple, fingers crossed for you.

 

I probably won't really do any "mods" as I'm not really into all that. The car came with a K & N CAI on it and that is enough for me LOL. I just want to track down this code and I hate driving a vehicle with the CEL illuminated.

I haven't done a pressure test yet I was losing coolant somewhere but I threw in some Bar's Stop Leak and that seems to have cured that problem. I know some on here at not fans of those types of additives but I have had great success with them and have used Bar's in about 3-4 different vehicles with no ill effects. So as of right now I'd have to say I do not have a coolant leak. Although if it was leaking internally it may have toasted that cat prior to me putting in the Stop Leak. I have a friend that has access to a coolant pressure tester at his business so I can get that done for nothing if I choose to.

The front one was a little sketchy when I bought it. I got it off Amazon and the dude described it as "used like new" and I trusted that description but I'm not sure it was actually "new" when I got it OR that it didn't have a problem. I can get a brand new one for about $30+ on Amazon at the moment so I'll pick up another one if that front one is indeed bad.

 

It's probably throwing the code because the 'universal' cat flows better and the o2's are reading higher flow.

 

That is exactly what my nephew was telling me. He said cars now a days are made with such "tight" emissions controls that on anything past about '98 a universal cat will make the car "whine" (as in cry like a baby LOL) that the specs aren't what they are supposed to be.

 

2 questions does this will at@ overkill have an email? i wouldlike to ask him a question, and has anyone have experience with these 02 emulators?

 

willoverkill@gmail.com

that is the email address I used when dealing with Will in October of last year. I just checked his site and it's down, so hopefully he is still doing this thing and it is just a server malfunction

He was posting on the forum a few weeks ago

 

With the p0420 code (cat below threshold temp) and the car running kinda fine... and there are no leaks at the cat. The problem actually is caused by your cold air intake giving you a lean condition. This is a problem when and changes are made to any computer controlled engine, their owners do not monitor and adjust the fueling as required by the changes. A simple vacuum gauge can tell if a cat is bad, watch it at idle 16-18" or better and note the vac then bring it to 2500 rpm (steady) and watch it if the vacuum starts to drop over 3-5 min then the cat is useless if it remains sort of in the same range it is good. If the vacuum is low at idle and remains low or gets lower at the steady 2500 rpm the exhaust has a blockage of some sort.

 

^^^^^^
Good info, but a slight correction...

If the cat is clogged the needle on the vacuum gauge will rise and fall rapidly (fluctuate). This is caused by the pulses created in the (restricted) exhaust stream as each cylinder purges. This test is a good indicator of a clogged cat, but a pre and post cat pressure test should be done to verify.

 

Good info. I have never ran a CAI filter on a car in the past. When I saw this one I was like the "what the hell is this"?

One noticeable thing when I replaced the original cat was that I was getting a P1811 I think it was which was a tranny code and terrible acceleration with "bucking" and "jerking" off the line and very hard shifts. I also had very bad performance and could hardly make the tires squawk if I wanted to. Every one I took the car to told me the same thing "the tranny is toast and needs to be replaced". Needless to say I replaced the cat since it was plugged and the tranny has been shifting fine ever since. Pluse I have plenty of power now. I have not noticed that "hard shifting" since replacing the cat HOWEVER I did notice the other day a little "buck" off the line at a red light. So at this point I won't rule anything out until I get some conclusive tests done. I'm curious if its just the code being thrown or if I have something i.e. a bad cat or bad O2 sensor or like you said if its the CAI filter causing problems.

 

Your little buck off the line could be just a dirty induction system, partially from oil residue released by the CAI. Another thing to consider is oxygenated fuel or even ethanol in the fuel causing a leaner condition by itself. The computers are designed to compensate some. Now in the early 2000`s ethanol was a consumer option but today it has been mandated to go as high as 30% without your knowledge. This fuel changes the burn characteristics that older computers cannot adjust for. Same goes for the spark plugs the factory installed a plug that was meant for real fuel not this ethanol stuff... what to do here is install a iridium plug that is 1 step colder than stock this will bring the fuel burn back in the combustion chamber, help relieve knock and return the power and performance to where it should be.