418whpturboD

ok my gfs 00 si keep throwing a code of o2 sensor.. it keeps throwin the check engine light.. i have changed both o2 sensors so it has both sensors brand new..what could be the problem.. i unplug ecu to reset and the light will stay off for a little bit but will come on again later.. any help wud be greatly appreciated..

roachsboosted16

wen i switched headers awhile back my car was doin the same exact thing, i think my problem was bcuz i didnt have a cat in between them on my d16, that probly isnt the problem in ur case. get some dummy sensors and solve all the cels.

418whpturboD

ya it wasnt doing it till i put a header on it also.. but have changed the sensors after putting header on.. it still has the stock cat and stock exhaust..

B serious

iTrader: (1)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by roachsboosted16 &raquo;</TD></TR><TR><TD CLASS="quote">wen i switched headers awhile back my car was doin the same exact thing, i think my problem was bcuz i didnt have a cat in between them on my d16, that probly isnt the problem in ur case. get some dummy sensors and solve all the cels.</TD></TR></TABLE>

buy a cat if that's the problem.

Car questions always sound so perverted when you're talking about someone's GF's car. Normally, you would say "is your CAT in good shape/present"? However, "is your GF's CAT in good shape/present?" is an unacceptable question, I think.
So:

Is your girlfriend's catalytic converter in good shape/ present?

418whpturboD

it appears to be i good shape.. it hasnt been alterd.. i have heard that if the cat is going bad/out it will throw codes... true??

Cln94EG1

Yep my friends 00 si started throwing codes cause his cat went bad changed it and now its all good no codes

B serious

iTrader: (1)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 418whpturboD &raquo;</TD></TR><TR><TD CLASS="quote">it appears to be i good shape.. it hasnt been alterd.. i have heard that if the cat is going bad/out it will throw codes... true??</TD></TR></TABLE>

The secondary O2 sensor is a monitor to check the CAT's presence and function. If the cat is missing or not functioning to spec, it will throw a code.

The primary O2 sensor controls fuel curve.

Which O2 sensor is throwing the code?

You should fix the problem at the SOURCE, not at the sypmtom. The O2 sensors going bad may just be a symptom of a problem. Like coughing because you have bronchitis. Cough syrup to fix the cough isn't going to help. You have to cure the bronchitis.

If the O2 sensors are going bad because the car is not running correctly, then fix that problem. If your car is running too rich, it will "clog up" the O2 sensors. If there are contaminants, like silicon from a coolant from a blown head gasket, it will contaminate sensors.

Has your gas mileage gone down? Any smoke? Which O2 sensor?

Libertariat

I would buy a replacement cat from Summit.

They have the best pricing I've seen. Universal cats are ~$70-90.

Direct fits are ~$130-150

418whpturboD

replaced upstream one still throwing code so replaced downstream one and its still throwin on check engine.. so would a high flow cat work???

B serious

iTrader: (1)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 418whpturboD &raquo;</TD></TR><TR><TD CLASS="quote">replaced upstream one still throwing code so replaced downstream one and its still throwin on check engine.. so would a high flow cat work???</TD></TR></TABLE>

I edited my post above. Read that.

A high flow might work. Somtimes cheap highflows will throw a check engine light. Some "high flow cats" on ebay are just test pipes. I think the people who sell those should be arrested.

I've heard good stuff about SMSP, but i've also heard they're expensive. Buy a quality cat whether you go highflow or stock.

Libertariat

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 418whpturboD &raquo;</TD></TR><TR><TD CLASS="quote">replaced upstream one still throwing code so replaced downstream one and its still throwin on check engine.. so would a high flow cat work???</TD></TR></TABLE>

you'd see no real gain from a high flow cat. Mostly only noise.

If you're looking for serious performance you don't want a cat anyway.

Get an OEM replacement IMO.

418whpturboD

she wants to change it but doesn't want any more noise...

B serious

iTrader: (1)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 418whpturboD &raquo;</TD></TR><TR><TD CLASS="quote">she wants to change it but doesn't want any more noise... </TD></TR></TABLE>

Go with an OEM replacement. $130-150 seems pretty reasonable....but only change the cat if you have to.

Have you actually hooked up a scan tool to see WHICH O2 sensor the code is being thrown for? From your above post, it just seems like you guessed. If you figure out which one it's being thrown for, you can make some sort of diagnosis.

Throwing money at it may or may not fix it. If it fixes it, great, you guessed right. If it doesn't fix it, you just wasted some $$. That being said, why dont you take it somewhere for it to be DIAGNOSED. There's gotta be a reason why the CEL keeps coming on.

However, if the CEL is coming on for a secondary O2 sensor, a faulty CAT is a pretty reasonable assumption. If it's coming on for the primary....there may be some other stuff going on. A stuck injector, burning oil, burning coolant, etc.

Libertariat

http://store.summitracing.com/...w=sku

Found one for you.