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will replacing cat with straight pipe cause engine malfunction?

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Old 04-27-2006, 07:56 PM
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Default will replacing cat with straight pipe cause engine malfunction?

I know that I'm a horrible nature destroying animal for even considering this, but I was just curious. I know when I forgot to plug my MAF sensor into my CAI, my engine fucked up in first gear and I had to reset the ECU. With a straight pipe, is the O2 sensor going to cause the same problem unless I do that one trick with it?

2005 4cyl coupe
Old 04-27-2006, 08:34 PM
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Default Re: will replacing cat with straight pipe cause engine malfunction? (Extremity)

The oxygen sensor monitor is your cat working or not.

you replave the oem cat with a straight pipe

o2 sensor notice the cat is not working

CEL triggered

Gas mileage goes down the drain and ecm trigger limp mode.


straight pipe on stock/NA bolt on car is USELESS and POINTLESS
Old 04-28-2006, 04:59 AM
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Default Re: will replacing cat with straight pipe cause engine malfunction? (iam7head)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by iam7head &raquo;</TD></TR><TR><TD CLASS="quote">Gas mileage goes down the drain and ecm trigger limp mode.</TD></TR></TABLE>
I agree with everything you said except that - the 2nd o2 sensor will throw a code but it will not put your car into limp mode or affect gas milage at all.
Old 04-28-2006, 05:03 AM
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Default Re: will replacing cat with straight pipe cause engine malfunction? (notoriousB)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by notoriousB &raquo;</TD></TR><TR><TD CLASS="quote">I agree with everything you said except that - the 2nd o2 sensor will throw a code but it will not put your car into limp mode or affect gas milage at all. </TD></TR></TABLE>
And I disagree with that. Your gas mileage is going to be affeted. BTW the converter on that car is part of the manifold and the second one is in the lower pipe.
Old 04-28-2006, 05:40 AM
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Default Re: will replacing cat with straight pipe cause engine malfunction? (Extremity)

when people like you want to do something stupid like this, law makers will make it even more difficult to modify our cars legally.....

Thanks for screwing it up for the rest of us..........
Old 04-28-2006, 05:51 AM
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Default Re: will replacing cat with straight pipe cause engine malfunction? (MooGoCow3)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by MooGoCow3 &raquo;</TD></TR><TR><TD CLASS="quote">And I disagree with that. Your gas mileage is going to be affeted. </TD></TR></TABLE>
why would the milage be affected? the 2nd o2 sensor's function is only to verify if the cat is working.

removing the cat will not affect gas milage.
Old 04-28-2006, 06:58 AM
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as soon as P0141 is set then the car is going to run more rich or lean to try and compensate for the converter it thinks is "deteriorated"
Old 04-28-2006, 08:56 AM
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Default Re: (MooGoCow3)

how would adding/subtracting fuel make any difference at all to the cat converter function??!

have you ever tried this yourself? I have and it made ZERO difference in the way the car runs or consumes fuel.
Old 04-28-2006, 09:06 AM
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Default Re: (MooGoCow3)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by MooGoCow3 &raquo;</TD></TR><TR><TD CLASS="quote">as soon as P0141 is set then the car is going to run more rich or lean to try and compensate for the converter it thinks is "deteriorated"</TD></TR></TABLE>

well buddy, the post cat o2 sensor has no affect at all on the fuel economy... that's just the pre-cat o2 sensor.

becuase the cel for the cat not working effectively will just say "Hey your convertor isn't working." Not, your gas mileage goes down the drain.

I may not know everything about Hondas, but that's computerized automobiles in general right there.

And the straight pipe on an EFI Stock 4 cylinder... It is useless... You aren't going to be doing anything that could even possibly damage the convertor.

Although if you decide to put a straight pipe on, just use either on o2 simulator or just find the correct resistor to put in the line so that the computer reads a 450mV(Ideal stoichiometric voltage) signal from the post cat o2 sensor.

That makes it so that you have no CEL and no worries unless you have to pass a sniffer test in your state.

Just my $0.02.
Old 04-28-2006, 09:59 AM
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Default Re: (97AccordProject)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 97AccordProject &raquo;</TD></TR><TR><TD CLASS="quote">

That makes it so that you have no CEL and no worries unless you have to pass a sniffer test in your state.

</TD></TR></TABLE>

exactly. you wont be able to pass your state's inspection...which really sucks.
Old 04-28-2006, 01:12 PM
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Default Re: (specbb6)

your gas mileage wont be affected trust me i had a 'test pipe' on my car in principle it should affect it but it doesn't. but there is no point in having a test pipe on your car imo, just save your money buy a complete exhaust and get a hi-flow cat. oh and another draw back with a test pipe is that you car will be noisy as hell and sound raspy. oh and you wont pass emissions, you could probably find a hi flow cat for the same price as a omni test pipe ($100)
Old 04-29-2006, 08:29 AM
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Default Re: (mattf22b1)

My state doesn't have emissions. But why run a straight pipe unless your running a turbo or have the motor seriously built.

One of my cars has no cat though and it doesn't make any differance in performance at all. the exhuast is just louder.
And gas mileage stayed the same. but it's a 90 accord ex so it's not exactly the same situation.
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