so i replaced the rattling cat with a test pipe and ever since the car sputters and bucks when its cold. around 3K rpm it seems to jerk and sputter through 1st 2nd and 3rd untill it gets to full operating temp and its fine. anybody have this issue? I tried to disconnect the battery for a few minutes to see if that would help Damn it sounds better but cant say it runs better someone help a fool out

it ran fine with the catback installed with the crappy cat but couldnt take that rattling noise, so after the test pipe install was when it acted up

 

You took the cat out and now the car doesn't run right....pretty straight-forward, isn't it?

Your car has emissions equipment that relies on the cat to maintain the optimal A/F for power and efficiency.

EDIT: The above statement is incorrect


Modified by Hawkze_2.3 at 11:57 PM 4/26/2008

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Hawkze_2.3 &raquo;</TD></TR><TR><TD CLASS="quote">Your car has emissions equipment that relies on the cat to maintain the optimal A/F for power and efficiency.</TD></TR></TABLE>

Like what?

 

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

Like what?</TD></TR></TABLE>

Like the ECU and the 02 sensors for example. Didn't we do this a while back

 

Yeah, I think so. But anyway, the cat and secondary O2 sensor don't have anything to do with running the engine.


I don't know why the car would F up so much if it was throwing a secondary o2 related code, if you even are. Pretty strange. You sure nothing else changed?

 

the o2 sensor has to heatup before it makes any corrections. My guess is that the engine is running leaner since changing the exhaust and cat would allow the engine to breathe better with less back pressure and the ecu cannot adjust for this until the o2 sensor is warm and active aka closed loop. the engine runs in open loop (no o2 sensor) until it is at operating temperatures. The ecu uses set fueling and ignition requires during startup depending on intake temperature and engine coolant temperature from the respective sensors.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by A Blue Lude &raquo;</TD></TR><TR><TD CLASS="quote">Yeah, I think so. But anyway, the cat and secondary O2 sensor don't have anything to do with running the engine.</TD></TR></TABLE>

So if I go remove my cat and secondary 02 sensor the car will run exactly the same as with them? If so, then I stand corrected....

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Hawkze_2.3 &raquo;</TD></TR><TR><TD CLASS="quote">

So if I go remove my cat and secondary 02 sensor the car will run exactly the same as with them? If so, then I stand corrected....</TD></TR></TABLE>

I didnt remove my cat, i replaced it with a test pipe. I didnt remove my O2 sensor either its still in the factory location.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 98vtec &raquo;</TD></TR><TR><TD CLASS="quote">the o2 sensor has to heatup before it makes any corrections. My guess is that the engine is running leaner since changing the exhaust and cat would allow the engine to breathe better with less back pressure and the ecu cannot adjust for this until the o2 sensor is warm and active aka closed loop. the engine runs in open loop (no o2 sensor) until it is at operating temperatures. The ecu uses set fueling and ignition requires during startup depending on intake temperature and engine coolant temperature from the respective sensors.</TD></TR></TABLE>

This makes more sense to me. Thanks for the input.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by ZUL8R &raquo;</TD></TR><TR><TD CLASS="quote">

I didnt remove my cat, i replaced it with a test pipe. I didnt remove my O2 sensor either its still in the factory location. </TD></TR></TABLE>

A test pipe is a hollow pipe replacement for a cat. If you install a test pipe, then you no longer have a cat.

 

oh boy here we go

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by ZUL8R &raquo;</TD></TR><TR><TD CLASS="quote">oh boy here we go </TD></TR></TABLE>

??

he is very right. You are no longer filtering the exhaust of harmful gas which is pretty damn pointless for a street car. thanks for increasing global warming

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by ZUL8R &raquo;</TD></TR><TR><TD CLASS="quote">oh boy here we go </TD></TR></TABLE>

What do you think a test pipe is?

Here ya go:






Test pipe = hollow pipe, no catalytic converter inside.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 98vtec &raquo;</TD></TR><TR><TD CLASS="quote">he is very right. You are no longer filtering the exhaust of harmful gas which is pretty damn pointless for a street car. thanks for increasing global warming </TD></TR></TABLE>

Of course, cat converters are designed to make CO2, a greenhouse gas, out of things that afaik are not so much greenhouse gases

 

Make sure you didn't damage the heater wires for the O2, all four wire sensors contain a heater circuit. Not to discredit anyone's opinion about secondary O2 sensors, but everything I learned so far from personal experience and my two years at AutoZone; on MOST vehicles the secondary O2 sensor only determines whether or not the catalytic converter is doing its job. Usually this does not affect the a/f ratio at all. When a customer comes in to have a "check engine" light diagnosed after removing the cat or installing a test pipe, the code returns "catalyst efficiency below threshold". Car runs exactly the same and only downside is the light itself. If the car's computer would try to compensate for this code it would most likely start throwing codes such as "bank 1 too rich/lean" try to return the cat's ability to clean the exhaust. Take in to consideration I said specifically MOST vehicles. Newer cars with the CAN emissions control system may try to repair the catalyst's efficiency.

PS- The main O2 sensor my just be taking a little longer to heat up from the lack of heat that was previously being provided by the slight blockage of the cat.


Modified by no1knows908 at 2:03 AM 4/27/2008

 

/\/\ Good info, I totally stand corrected on how I thought it worked. I figured no cat + OBD2 = engine not running right....learn something every day

 

Thanks for the credit, but I owe most of what I learned about the subject from all the a$$clowns around here with 6 cylinder trucks assuming that cutting out the cat will make their truck sound like an 8... And in all honestly all it does it make their exhaust sound raspy as hell and pop on the downrev.