SES: O2 or headers

[borispeed]

Re: SES: O2 or headers

3- Running rich will kill a CAT, the after cat O2 could be bad and is cheaper than replacing the CAT again. Can you pull the CAT off and inspect it?
My mileage went up over 3 MPG with headers, high flow CAT and CAT back.

The cat is not direct fit, it was welded to the pipe.

[borispeed]

Re: SES: O2 or headers

1-Fix you exhaust (EGR) leak. That will give false information to the O2 sensors.

2- Check the fuse for the O2 sensor, if blown replace it, if not replace the O2 sensor. Bank 1 is the drivers side.

3- Running rich will kill a CAT, the after cat O2 could be bad and is cheaper than replacing the CAT again. Can you pull the CAT off and inspect it?

My mileage went up over 3 MPG with headers, high flow CAT and CAT back.

Probably I'll do 1, 2, 3, and if this does't work, then I'll replace the cat

[borispeed]

Re: SES: O2 or headers

Thanks guys for your help.

[Gatt9]

Re: SES: O2 or headers

I have an update in this issue. I went to autozone and I got 2 codes: P0420 (Catalyst efficiency low bank 1) and P0135 (HO2S 11 - Heated Oxigen Sensor Bank 1 sensor 1).

As I said, a year ago headers were installed, what I forgot to say at the beggining of this thread is that I have a leak in the connection of EGR tube and headers, same story that some of you are dealing with. Also when I did headers, I did high flow catalyc (Dynacat) too that is off-road but complies with OBDII (according with the manufacturer). So far the car is running great, with a decrease in fuel of about 4 or 5 mpg.

So about the codes, the autozone computer gives the following probable causes:

P0420
1 - Catalytic Converter defective (failure possibly due to #2, 3, or 4)
2 - Engine misfire or running condition.
3 - Large vacuum leak
4 - Engine oil leakage into exhaust-valve guide seals piston rings.

P0135
1 - Oxigen sensor defective.
2 - Poor connection at oxigen sensor
3 - Check circuit fuse

I need your help guys, What do you think?

You seem to have the *exact* same problem I have.

EGR leak -> O2 sensor -> Cat code.

I fixed the leak, replaced the bank 2 O2 sensor, I still have the code. As Brian and others pointed out to me, bad O2 sensor makes car run rich burns out Cat. Mine went *really* bad, and I'm certain at this point that I need a new cat.

I'm going to replace the other 2 O2 sensors at this point when I get the cat done.

Get yourself some JBWeld or the Copper stuff, coat that EGR good. It'll seal it.

But I'd guess you'll be in the same boat I'm in and be doing the cat. Btw, check my post history for a thread on O2 sensors. I ended up with some really nice Denco's for half the price of the Autozone's each from forum member's help.

[borispeed]

Re: SES: O2 or headers

You seem to have the *exact* same problem I have.

EGR leak -> O2 sensor -> Cat code.

I fixed the leak, replaced the bank 2 O2 sensor, I still have the code. As Brian and others pointed out to me, bad O2 sensor makes car run rich burns out Cat. Mine went *really* bad, and I'm certain at this point that I need a new cat.

I'm going to replace the other 2 O2 sensors at this point when I get the cat done.

Get yourself some JBWeld or the Copper stuff, coat that EGR good. It'll seal it.

But I'd guess you'll be in the same boat I'm in and be doing the cat. Btw, check my post history for a thread on O2 sensors. I ended up with some really nice Denco's for half the price of the Autozone's each from forum member's help.

Thanks Brian for your response. I hope my cat is still alive. Dynacat has only a welded honeycomb inside, and you can look through it daylight and other stuff from outside from one edge to the other. It looks very resistant. There's no extra stuff that can be damaged like other cats. Keep my cat in your prayers. :bowdown:

[auto666]

Re: SES: O2 or headers

looking at or threw a cat wont tell you if its functioning properly check it with a infered thermomitor to make sure its lighting off

Narrow band 02 sensors dont read exact at any ratio and 14.7 to 1 is what it should be at idle or cruz it richens up when you accel and leans on decel
all a narrow band will show is rich or lean it just bounces back and forth around 14.7 to 1, putting you in the general area of 14.7 to 1 which is for emmisions by the way it gives the best burn for lowest emmisions under light or no load