Need Some Help
 

Okay.. So here are the basics, I have a 2001 2.4L with a WAI and pacestter header with the full 2.5in cat back system. I also put on a magnaflow high flow cat. Everything was fine until the rear O2 sensor went out. The car threw a code and started stumbling really bad. So I read the code and found out that the sensor went bad, so I replaced it. The code cleared, but the stumbling continued. I figured that it would hopefully smooth back out. Then about a week later it threw another code, this time for the cat. So i had it temp tested and it wasn't firing. I then pulled it off to find it full of carbon, really bad. It seems like I have been running really rich and it fouled the cat. So I need some help finding out why it is running so rich, and if this is what's causing the stumbling. Any suggestions would be greatly appreciated.

check your plugs to see what they look like...., could be fouled plug, bad coil pack, could be map sensor related, could be front o2 sensor related................make sure you don't have vacuum leaks.........

start w/ that.

Well here is the thing now that you have the high flow cat your exhaust velocity increased and to top it all up, you went from a manifold that had the 02 sensor reading all cylinders to a header that only reads 1 cylinder. The sensor in the cat doesnt affect performance it just tells the computer that the cat is working, if your cat now is stright thru the o2 sensor in the cat is always goin to fry faster now cause now is reading higher temps that the sensor cant handel.
One thing you can do is wire your own heated o2 sensor for the o2 on the header and this will solve your running rich problem since the o2 sensor thats on your car right now is taking forever to heat up from only one cylinder, thats why you are running rich plus you are only reading one cylinder AFR.

Well I replaced both of the O2 sensors at the same time, about 2 months ago, and the front O2 sensor is in the collector pipe so it should be getting all 4 cylinders, right? Also I just replaced the plug about 5 months ago with Bosc platinum 4's. And i just checked all the vac lines and it all looks good. And I didn't think the 2.4 had a MAP sensor only an IAT and that i think is okay..

That's the first mistake. Waste-Spark ignition systems typically don't work good with bosch platinum series plugs.

Really? What plugs should I change to?

Ac Delcos

ya man the stock ac delco are pretty good

i like my NGK's personally... and they arent very expensive.

X 2 dont run bosch at alll........... never. Run some autolites youll be fine.

Okay, I will change the plugs tomorrow.. Hopefully that will help.

autolites all the way.:scpimp:

i know that i said this before people buying nkg plugs are buying the samething as ac delcos
look at a ac delco and it has stamped on the metal part ngk
plus also has stamped the gm part number

I think that's only the iridium plugs that are made by NGK for ACDelco.

NGK for the win.

Okay.. So I went with the NGK Iridium IX.. It seems to be doing a little better, but I can still tell there is something wrong, still a slight trembling, and it just threw the Cat code again.

How many miles on car, have you had your injectors cleaned lately? Have you had your coil packs checked out at all?

What is the number that comes up when the code is read? That would help us help you.

It's a 420 code, cat Inefficiency. It has 84000mi and I have run injector cleaner through it about every 5000mi or so. I haven't had the coils checked yet, I wanted to get some opinions before I spend $100 for a diagnostic.

Okay.. So i got the diagnostic this morning. They said the main issue is that the upstream O2 sensor isn't heating up enough and that's causing it to run too rich. They said that the Bosch sensor that I just installed isn't good for the header and exhaust setup. They suggested that I go with a Delphi sensor and that should fix it. Also they said that the fan is turning on low sometimes when the car is cold. They said it shouldn't turn on until the operating temp, which is like 220, is reached. Its not always, but it might also be causing it to run to cold, which would cause it to run rich. I was wondering if any one has any input on this, or if any one has had similar issues? Any suggestions would be awesome.