I have a 2001 Z24 and i just got my full exhaust put on like a couple weeks ago....and ever since i got my header and high flow cat put on ive had a check engine light on with the code o2 sensor malfunction so i got a new front (header) o2 sensor and cleared the codes and after a little driving it came back up....Now my question is if i get an o2 simulator it will bypass the sensor after the cat so if that one is indeed causing the problem maybe from the amount of air flow then will it take that code away??? Cuz i need to pass inspection next month...lol

1 big thing , you gotta KNOW WHAT THE CODE IS !!!!!!!


before you do anything , you havent even said if its front or rear


so before you talk o2 sim , gotta know if its B1S1 or B1S2

just a heads up if you are looking at the one rksports has unless they have fixed it in the last 2 months it doesn't work on any 2.4's past I think it was 98 or 00. They didn't even tell me that I had to contact casper electronics. Before I found that out rksports just kept on sending new ones thinking they were just defective.

Woah woah woah.... I just put $50 down towards a "RKSport header 2.4" slightly used that he can't confirm ever threw any codes (apparently he got it from a friend?)

The price is so good I couldn't refuse ($100 plus $20 shipping) but if it's gonna keep me from passing inspection... I mean I'd have til July to sort it out but if I could get the pacesetter header for the same price (and have it rust off in a year) then I will do that...

someone let me know please what the actual deal is with that.

Also is this even the RKSport header? Can anyone confirm? He hasn't answered me about how he's "sure" it is the RKSport one...

is there a schematic on how to build a 02 sim on the net somewhere?


saturn 5speed turbo 8psi
93' z24 grand prix turbo 3.1 swap, crane 272 cam, 3100 hybrid top end swap, t04b turbo

my bad not the rksports header that I was having problems with it was there O2 simulator thats not any good

When I removed my catalytic converter on my 99 Z24, car threw the P0402 code (I think... it was a long time ago), and the car felt sluggish and unresponsive, so I got the Casper O2 sim from SummitRacing.com, part # CEI-104046 if you're interested. It took care of the CEL immediately and for good. I unplugged the battery and let the computer reset at the same time, so when I first ran the car with the Sim, it performed flawlessly... but after a while it felt like the computer was starting to gradually remap itself and the Sim was causing the car to be sluggish and slightly less responsive... even worse than when it was when I had the CEL.

In summary, if the code you're getting is indeed related to your new high-flow converter, the sim will most likely take care of it, but might cause your car to perform worse.

So the real question is, what high-flow catalytic converter are you using? If it's a Magnaflow 940xx series cat, then you should not be throwing any codes if installed and hooked up correctly, so the problem may lie elsewhere. There's a thread about an alternative to the O2 Sim, it's some method of using a spark plug anti-fouler to space the second O2 Sensor farther out of the converter so it doesn't get confused and get bad readings because of the much higher rate of flow (if I remembered all that correctly). Here's the link Mechanical O2 Simulator($5 mod that WORKS for 96+) You may want to try this out instead of the Sim... I know nothing about it's effect on emissions testing but myabe it's covered in that thread.

i got a question also i did the same putting pacesetter headers and full exhaust and it came up that O2 sensor 1 and 2. something like that it was a long time. i have been driving with the engine light on since then. also i change it and the light with the same codes came up O2sensor 1 and 2.
my mechanic says is a computer problem. my brother says that i have to me a flush something like that.
i dont know what is the problem really

Can anyone confirm what type of header is in those pictures I posted, what part I will need to get in addition to attach it to the Cat, and if it looks to be in perfectly usable condition?

Jesse D wrote:Can anyone confirm what type of header is in those pictures I posted, what part I will need to get in addition to attach it to the Cat, and if it looks to be in perfectly usable condition?

Looks fine in the pics, but it's hard to tell just by those pics. Couldn't confirm which header that is exactly. It came with a collector pipe, right? Just one solid pipe that attaches to the main 4-1 section? You'll need that to attach it to the converter, of course. Additionally, visit Advance, Autozone, O'Reilley's, NAPA, or whichever auto store you want and get a new exhaust manifold gasket. Do not reuse the gasket alreay on your car. You never know if it's already ruined and it will leak if it is. Gaskets seal 2 things together by being crushed into the shape of both things as they're tightened together, so 1 - it's already been crushed, and 2 - it may not seal well on the new header because the surface of the flange is different than the surface on your old manifold. So pick up a new stock replacment exactly like your old one. This header will of course have to be welded to your converter, so invest in a U-clamp or a band clamp (preferable, won't crush pipes) of apropriate size to attach the collector pipe to your converter temporarily while you drive to an exhaust shop to have it welded. The pipe on the converter or the collector pipe may have to be cut / trimmed to the right length to get both ends to mate-up correctly fo you to clamp them together. If you really feel like it, invest in a new O2 sensor (the one that goes in the header). Old sensors can be uncooperative when removing them from the stock manifold, and there's always the chance you'll damage it during removal. Besides, it never hurts to have a new sonsor anyway. I thinkI paid in the $30 neighborhood for that sensor... the one in the converter was a lot more expensive though...

That's all I can think of now...

Ok so I have already put $50 down towards this header - and no it doesn't come with a collector pipe - the seller claims he took it from a friend's car who was running "open header" (that's his reasoning for no collector pipe)

The total cost for it used is $122 after shipping... for a mystery header with no collector.

Since people are saying the pacesetter 4-1 header isn't bad maybe I should scrap this purcahse, and buy that one instead, so I will have a collector pipe. What do you think? I also plan on buying a hi-flow cat that is OBDII compliant... so I can just buy the pacesetter (or this one?) and that cat-converter and an exhaust gasket and take it all to a shop?

Jesse D wrote:Ok so I have already put $50 down towards this header - and no it doesn't come with a collector pipe - the seller claims he took it from a friend's car who was running "open header" (that's his reasoning for no collector pipe)

The total cost for it used is $122 after shipping... for a mystery header with no collector.

Since people are saying the pacesetter 4-1 header isn't bad maybe I should scrap this purcahse, and buy that one instead, so I will have a collector pipe. What do you think? I also plan on buying a hi-flow cat that is OBDII compliant... so I can just buy the pacesetter (or this one?) and that cat-converter and an exhaust gasket and take it all to a shop?

I can't imagine why someone would run open header on an N/A car... you're not getting the whole story here. And I can only imagine the condition of the end that's supposed to meet the collector if it indeed was run totally open. Yikes. If you can get your $50 back, do it and hold out for a REAL header. $122 is a joke for a only HALF of a USED header. For not too much more you could end up with a complete Pacesetter painted header brand new.

Yes, go with the Pacesetter header, not that other POS:
- Pacesetter 4-1 Painted header - $144 @ TurboTechRacing.com, may be cheaper elsewhere.
- Fel Pro exhaust manifold gasket - $10 @ Advance Auto Parts
- 2 Regular U-Bolt clamps - $2-3 @ Anywhere
- Magnaflow OBD-II Converter, 2.25", Part # 94035 - $68 @ JustMagnaflow.com
Part number is important here!
TOTAL between $200 and $250

And if you have to change either of the O2 sensors:
- Bosch Upstream (in header) O2 sensor - $68 @ Advance Auto Parts
- Bosch Downstream (in converter) O2 sensor = $72 @ Advance Auto Parts

BTW, the converter needs to be welded onto both the header and the cat-back section but you might not have much luck trying to clamp the converter on both ends, since the cat-back section has a 3-bolt flange you'd need to cut off first (hi-flow converter does not have flange)... but then it MAY not reach, so unless you can weld you need to install just the header, and clamp it to the STOCK converter, drive to exhaust shop, and have THEM install and weld up your converter.

I would agree about the new O2 sensor in the header. After I ditched the O2 simulator I just replaced the sensor in the header and reset the computer (apparently the idiot at auto zone didn't know what the code meant that I was throwing) hooked the original back up in the cat. Havn't seen the check engine light again since and thats been almost 6 months ago.

Jesse D....ive been lookin at that header....why is the o2 sensor hole up top on one of the pipes and not where all the 4 pipes meet (like normal)....maybe im seeing things wrong...and if i was a pacesetter my pacesetter has welded on it a plate saying that it is a pacesetter....i dunno what header that is but it looks pretty torn up....id go and buy a pacesetter header.....the problems i was having at the top of this thread was because i started out with a tsudo header which messed up everything but now everything is fine since i got the pacesetter i just need to reset my comp.

Yeah I didn't end up buying it, got my $50 back (well $46 thanks to paypal) and I'll just get the pacesetter one when I'm ready to do my exhaust... now I just need to buy some performance valves for my cams...

Jeff Ensor wrote:Jesse D....ive been lookin at that header....why is the o2 sensor hole up top on one of the pipes and not where all the 4 pipes meet (like normal)....maybe im seeing things wrong...

The O2 sensor bung on my DC Sports header is way up in one of the primary tubes, not near the collector, and it hasn't caused a problem. Guess it makes no difference.

ok im adding on to this topic i have a 97 2.2ohv and i have stock header and down pipe with a no name high flow cat with the rksport duals. i have the o2 sensor in the header but the one that goes by the cat i dont even have at all i ordered an rksport sim along time ago and it never worked i would like to get new sim that will work not a waste of time again!! so what im wondering is if anyone has a link to buy a sim that really works or to make one!! im not sure what codes pop up i will scan it tomarrow and write it down but i no its throwning up to codes about catalytic bla bla bla i will get them and post it thanks alot!

Jesse D
You could just got to your local exhaust shop and buy a pipe with the collector for like 5 dollars.

Cale Green wrote:ok im adding on to this topic i have a 97 2.2ohv and i have stock header and down pipe with a no name high flow cat with the rksport duals. i have the o2 sensor in the header but the one that goes by the cat i dont even have at all i ordered an rksport sim along time ago and it never worked i would like to get new sim that will work not a waste of time again!! so what im wondering is if anyone has a link to buy a sim that really works or to make one!! im not sure what codes pop up i will scan it tomarrow and write it down but i no its throwning up to codes about catalytic bla bla bla i will get them and post it thanks alot!

Do a search for manual O2 sim, it will cost $5-10 tops and works.



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