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Sierra 6.2L Exhaust questions

  
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Sierra 6.2L Exhaust questions

 
nickkoopman nickkoopman
New User | Posts: 3 | Joined: 01/14
Posted: 01/21/14
12:12 PM

New to forums so don't hate.

2007 Sierra Denali AWD 6.2L

Engine light is on. Scan tool is showing cat code. Truck has 3" from the Y pipe to a side dump in front of the right rear tire through a Borla 3" race muffler. Y pipe and manifolds are stock. I just changed the rear O2 sensors at 100000 miles, so my thought process is i was wondering if the factory cats were not receiving enough back pressure with the side exit to allow the cats to work properly? And if the case would a header hi flow cat/y pipe set up work better and clear this code. Def don't wanna go back to a boring factory set up  Laugh


Any help or suggestions would be appreciated  

wayne712222 wayne712222
New User | Posts: 33 | Joined: 10/13
Posted: 01/21/14
01:04 PM

what code...

do you have a scan tool that will not just display live data.. but will graph the data stream???

get into the live data...

O2B1S1

O2B2S1

and

which ever O2B?S2 or O2B?S3

get the first sensors up one at a time.. push the enter button to get it into graph mode.... once there.. take the engine to 2500 RPM.. hold the throttle totally still.. DO NOT MOVE YOUR foot.. see if the oxygen sensor starts swinging fully from 0.01 to 0.8 volts.. nice swings..  then slowly let off.. it should continue to swing full nice patterns. take 20 seconds to back off to idle..

this shows that the oxygen sensors have the ability to look at the exhaust flow and the fuel system is in feedback loop properly..  

the oxygen sensors after the cat are to monitor that the cat is working properly..


if you have exhaust leaks.. you can get dilution issues and it will throw P0420s.. but you did not mention the codes..

you should also look at the short term and long term fuel trims..

if your truck is running properly.. it should be within 10% either plus or minus..  

nickkoopman nickkoopman
New User | Posts: 3 | Joined: 01/14
Posted: 01/22/14
09:29 AM

Sorry was working nights.


Here are the codes P0420 and P0430

and each 02 sensor reading after the 2500RPM to idle test

02S11 .017 to .805 with a nice sine wave pattern

02S12 .608 to .668

02S21 .049 to .848 with a nice sine wave pattern

02S22 .579 to .715

ST FTRM -9.3 to 7.3

And i Don't have a clue what the cats should be at operating temp but they were as follows

cat temp 11 928 Degrees F

cat temp 21 943 Degrees F

After the testing.  No obvious exhaust leaks its -22 Celsius  

wayne712222 wayne712222
New User | Posts: 33 | Joined: 10/13
Posted: 01/22/14
10:00 AM

hotter coming out is good...

exhaust and smog techs look for 100F hotter on the outet at 2500..

what about the fuel trims..

i see a small difference in your oxygen sensor readings...

is one side leaner than the other when looking at the short term and long term fuel trims.. for bank 1 and back 2.???

when you dropped the engine speed back to idle slowly.. did both sensors still have a decent wave form???

and can you look at the wave forms of the secondary sensor.s  O2S12 and o2s22

is there any chance of a vacuum leak.. ??? loose hose.. oxygen sensor wave forms will tell you.. they should NOT be flat lined after coming down slowly from 2500 test..  

wayne712222 wayne712222
New User | Posts: 33 | Joined: 10/13
Posted: 01/22/14
10:06 AM

oh... -22C.. burrrrrrrrrrr..

its umbrella weather here in los angeles.. low 80s...  but it has not rained in a while.. we are at less than an inch.. and are normally at around 6 inches.. 25MM when we should have about 150 mm..

there is  a trick using anti foulers on the secondarys.. 2 on each. top one drilled to allow room for sensor.. slows the signal down..

can your scan tool hook to your PC .. and record a 2500 run and a idle run???

post the data... its too much to type  

nickkoopman nickkoopman
New User | Posts: 3 | Joined: 01/14
Posted: 01/22/14
10:17 AM

Ill take the -22.  Looks like it can record live data gonna research that and hopefully the MacBook doesn't complicate things.  

wayne712222 wayne712222
New User | Posts: 33 | Joined: 10/13
Posted: 01/23/14
12:48 AM

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