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  #13  
Old 11-10-2011, 08:51 PM
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Re: Remove CATS = Time Bomb ?

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Originally Posted by JeepMe View Post
The only thing I would imagine is that "downstream" means after combustion and "upstream" means before combustion (aka, intake MAF). Upstream would be the input and downstream would be the exhaust. The two downstream sensors should be one on the left exhaust and one on the right exhaust.

That's how nearly all engines work now. The front exhaust O2 sensors monitor the exhaust. Based off their reading, it will compare the MAF reading and change fuel until the down exhaust O2 sensors rear correctly.
Upstream means close to the combustion source and downstream further from the combustion event (post catalyst in this case). Jeeps are speed density tuned. As such they have no MAF to measure intake airflow which means that open loop fueling (PE mode and old starts) is calculated off MAP, load and RPM (aka calculated cylinder airmass) to determine injector pulse width. Closed loop fueling takes into account the readings from the upstream O2 sensors when calculating injector pulse width.
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Old 11-10-2011, 10:08 PM
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Re: Remove CATS = Time Bomb ?

Your Jeep is fine with or without cats! It's the front O2 sensors that matter!

I have no cats or any of that other emissions stuff on my Jeep.
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Old 11-11-2011, 12:17 AM
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Re: Remove CATS = Time Bomb ?

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Originally Posted by FlyinRyan View Post
Jeeps do not have maf!!!!!
Chrysler needs to get their shit together. The more I learn about these damn Jeeps, the more everything is different from all other vehicles.
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Old 11-11-2011, 01:22 AM
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Re: Remove CATS = Time Bomb ?

I downloaded a WJ Workshop Manual and this is what is says about the O2 Sensors :

Quote:
Upstream Sensors (California Engines): Two
upstream sensors are used (1/1 and 2/1). The 1/1 sensor
is the first sensor to receive exhaust gases from
the #1 cylinder. They provide an input voltage to the
PCM. The input tells the PCM the oxygen content of
the exhaust gas. The PCM uses this information to
fine tune fuel delivery to maintain the correct oxygen
content at the downstream oxygen sensors. The PCM
will change the air/fuel ratio until the upstream sensors
input a voltage that the PCM has determined
will make the downstream sensors output (oxygen
content) correct.
The upstream oxygen sensors also provide an input
to determine mini-catalyst efficiency. Main catalytic
convertor efficiency is not calculated with this package.
Downstream Sensors (California Engines):
Two downstream sensors are used (1/2 and 2/2). The
downstream sensors are used to determine the correct
air-fuel ratio. As the oxygen content changes at
the downstream sensor, the PCM calculates how
much air-fuel ratio change is required. The PCM
then looks at the upstream oxygen sensor voltage,
and changes fuel delivery until the upstream sensor
voltage changes enough to correct the downstream
sensor voltage (oxygen content).
The downstream oxygen sensors also provide an
input to determine mini-catalyst efficiency. Main catalytic
convertor efficiency is not calculated with this
package.
Engines equipped with either a downstream sensor(
s), or a post-catalytic sensor, will monitor catalytic
convertor efficiency. If efficiency is below
emission standards, the Malfunction Indicator Lamp
(MIL) will be illuminated and a Diagnostic Trouble
Code (DTC) will be set. Refer to Monitored Systems
in Emission Control Systems for additional information
So in effect all four sensors are used to calculate the correct A/F ratios. I'm going to try and have my A/F ratios monitored/measured to try and ascertain whether there is indeed cause for concern here ....
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Old 11-11-2011, 01:16 PM
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Re: Remove CATS = Time Bomb ?

Is your Jeep from California?

California has very strict regulations that the rest of the US doesn't.

Cats or no cats your Jeep is fine.
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Old 11-11-2011, 01:23 PM
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Re: Remove CATS = Time Bomb ?

Quote:
Originally Posted by 0l1v3r View Post
I downloaded a WJ Workshop Manual and this is what is says about the O2 Sensors :



So in effect all four sensors are used to calculate the correct A/F ratios. I'm going to try and have my A/F ratios monitored/measured to try and ascertain whether there is indeed cause for concern here ....
Nope just the 2 upstream O2 sensors. The rear one or two just tell the ECM if the cats are working properly.
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Old 11-12-2011, 01:39 AM
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Re: Remove CATS = Time Bomb ?

I am starting to get the impression that I am probably overly cautious here ...
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Old 11-12-2011, 11:55 AM
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Re: Remove CATS = Time Bomb ?

You're Jeep is fine without the cats. I myself and a lot of others that I know of and that have worked on vehicles for 15+ years have ran without them on various vehicles with no issues at all.
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