I have pacesetter headers a magnaflow hi flow cat and a magnaflow dual catback system and a month after putting the cat on I have thrown on a check engine light(cat below eficiency). I called maganflow and they say that their hi flow cats shouldnt do that for a 2.2 and should not require an O2 simulator but others say it does. I have replaced the o2 sensors and the code still reads cat below efficiency. Anyone else had this problem and can anyone vouch that an O2 simulator will fix the problem? Thanks for any and all help with this. By the way its also idling around 1100 rpm.

Can we have the part number on the catalytic converter you are currently using please?




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sure its the direct fit hi-flow cat part number 23499.

By the way the guy at magnaflow said to disconnect the battery to reset to computer but I already cleared the codes and they came right back.

What year is your car? If you have a 95 or 96, the better cat for your use with a 2.25" catback exhaust is part number 53005. (That's what I have and it's wonderful).




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Nope. Mine is a 97, and because I can't weld the direct fit was my best option. Any other ideas?

So I take it your factory cat had or did not have a secondary o2 sensor in the factory cat




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Yeah it had one, the magnaflow unit was exactly the same as the stack one right down to the o2 sensor hole, except of course its high flow.

OK. Well there is no point honestly, in buying a "high flow" cat that is the same dimensions as your stock cat, especially when you have opened up the rest of your piping another .25 inches

The car part number you want is 94035

Take it and have it welded in.


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Most of that makes sense, but the diameter of the cat should not throw engine codes and make the check engine light come on. At least that's what I would imagine.

Russell Kemp wrote:Most of that makes sense, but the diameter of the cat should not throw engine codes and make the check engine light come on. At least that's what I would imagine.

I can't explain that one, because quite frankly I have no idea. All I can do is give you advice on the part number that is best suited for your application, have you replace the rear o2 sensor (cheap) and reset your PCM




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I Changed the 02 sensors 2weeks ago and disconnected the battery last nite so we will see if that has any effect 2day. Just an idea but if that doesn't fix it, wouldn't it be about the same cost to get an o2 simulator and run 2.25 straight pipe through. Plus add a little power. The o2 sim is about 70 bucks and the welding costs should be similar. Just a thought.

Go that route and you will lose power. You will lose your low end torque. I paid $60 brand new in box for my high flow cat. I chose the right cat for my application and don't have any problems. I would highly not recommend the o2 sim and straight pipe. If that is your choice, let that be your choice. But I'll tell you right now. It's going to be extremely loud, raspy, illegal, and slow.




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Hey that's good to know, like I said it was just a thought. I don't need anymore attention from cops around here. Where did you order that cat from for so cheap?

Also to weld in that new cat they would have to cut the flanges from my downpipe and cat-back pipe right?

I ordered mine through a local shop. However, here is one on ebay for $67 and here is one for $69.99 from TurboTechRacing




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Cool, if the pcm reset doesn't fix it I will probably go that route. I thought about using that cat to begin with and didn't think about the diameter. It makes sense now that I should have just spent the extra $ to get it welded, but hindsight is always 20/20. Anyways thanks for all your advice it was a great help.

No problem man, let me know if you get it sorted out




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Russell Kemp wrote:I Changed the 02 sensors 2weeks ago and disconnected the battery last nite so we will see if that has any effect 2day. Just an idea but if that doesn't fix it, wouldn't it be about the same cost to get an o2 simulator and run 2.25 straight pipe through. Plus add a little power. The o2 sim is about 70 bucks and the welding costs should be similar. Just a thought.

I have heard of people with Hi-Flow cats getting codes. Do not buy the $70 O2 sim. There is a $5 manual O2 sim. This is what I would recommend in your case. If you do a search for O2 sim, there is a few different post on it. You can also email me and I can give you more info on it.



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