i kept seeing the same answers over and over. replace the front 02's i kept seeing, egr needs to be cleaned made more sense then that. i went to the dealer, ( as i explained ) and they had said because of my warpspeed y and the rear 02 being original ( 18 y/o ) through multiple exhaust setups that none of the 02's were reading?? but, they said the rear was more likely the culprit because of the age. allthough i will agree with the front 02's possibly being bad, they were both replaced within the last 4 to 6 years. so, does the fact that i have an aftermarket y with no pre-cats make the 02's void?

 

Your front o2s are placed in front of the cats originally so it wouldn't matter on those two.
With an old rear o2 and pre cat delete you might get a code from the tear o2.
Tell us what codes you have, along with a definition.

 

I don't remember from your last thread, you are making sure your engine is completely warmed up right? Colder engine temp/exhaust temp = high nox. You have to make sure your engine is warmed up ESPECIALLY since you don't have your precats. Have you cleaned your egr?(again, don't remember)

 

i have no codes, engine was hot when i took it in. did the k&n filter clean out today, frickin dirty!! put in some 93 octane today as well, seemed to be idling better. how do i know if i have my idle speed set properly? i know it's that little screw, is there a point where you know how high or low it should be? i see some op's idling at 750, i'm never higher than 500. but at warm up once or twice she shot up to 1500 after i allready drove her a good few miles. maf? think that's getting a clean as well tomorrow.

 

Your rear o2 does not effect emissions besides setting off a CEL. It is not used at all for engine operation or adjusting AFR. To me it sounds like a process of elimination until you find the reason your engine is not running right. Just a process of testing and cleaning components.

 

engine's running fine, somethings dirty and spewing out smoke a bit. im doing the rear 02 and replacing the cat again since its under warranty. it'll pass regardless cause of the waiver they give after you spend $150.00.

 

The rear O2 sensor definitely does not affect anything except turning your CEL light.

I drove around with the code for 2 months then I finally changed it because I got tired of seeing the CEL light on.

The rear O2 just checks if your CAT is clogged/working, but from what I can tell it seems like you might have a more serious issue.

From what I can tell it looks like you are running rich or burning oil if there is lots of smoke. But I don't know the whole story so I am not much help

 

Get a scanner on the car and look at the fuel trims.

 

had a test at the dealer, they said at start up im running rich and then after she warms up she's fine. so, i'm doing process of elimination, air filter cleanout, maf, rear 02 and cat, throttle body cleaning. i'm going to pass anyway, but i'd still like to get her running as good as possible.

 

Check if coolant temperature sensor is within spec.

 

The O2s read the oxygen in the exhaust.
The Cat converters change the CO and hydrocarbons in the exhaust to CO2 and water.

Their functions are independent and un-related, so a Y pipe with no precats means more CO and hydrocarbons going past the O2s. They eventually get cleaned out later by the main catalytic converter under the car.

So maybe a y-pipe would lead to O2 sensors getting fouled up sooner rather than later.

 

NO

The FRONT o2 sensors are located BEFORE the Y-pipe cats (precats), so NO the Y-pipe wont have ANY affect on those o2 sensors.
Having an aftermarket Y-pipe could cause a low catalyst efficiency code, as read by the rear o2 sensor due to 50% of your overall catalyst being gone.

FRONT o2 sensors have only one job, read the oxygen level in the exhaust and adjust the air fuel ratio going into the engine. If the pre-cats were placed before the primary o2s, they would read lean causing the ECU to run over rich.

 

so my question is, how do i get maxy to stop running rich and get the levels even? does timing affect the air flow ratio to run lean or rich? i assume anything to do with air flow can have an affect on emissions if not adjusted properly. what should/needs to be cleaned adjusted to get clean levels other than the usual? egr control valve, egr tube, emulate further.

 

to all of you op that said the cat did'nt affect nox, YOU WERE WRONG!!!! i replaced my cat and put a new 02 sensor in there and the nox went down 50%!!! i will post up the numbers before and after first chance i get, cars running better as well. i will have to see what the gas mileage change is if any. i also did the k&n cleanup and maf as well. i'm doing an injector service next week.

 

your original cat was clogged a bit, that makes sense as to why the new one works wonders comparatively.

I bet you're still running rich though.

 

Dont do an injector service...TC-W3 and take a jaunt on the highway man!
You replaced the front O2 only?

 

ummmm, does nobody read? the cat was replaced last year same time cause of the high numbers. i got another one cause it was warrantied for a year and i just got it in. and it was the REAR 02 in the cat i replaced, not the front. really not running that rich anyway, just at start up.

 

Didn't catch that part about being replaced already

 

sorry, sometimes i feel like a school teacher trying to teach rather than learn.