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Thread: O2 sensors

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    Member scottcmb's Avatar
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    Default O2 sensors

    Gidday I have a Stock 2002 Blazer 4.3 with a LS1B ecm.........could you guys look at my log to let me know if my O2 sensors are behaving normally or does it look like they are a bit sad and need replacing?. The voltage on both fluctuate up and down consistantly is this normal?

    Cheers ScottyO2 sensor log_0000.efi
    2008 HSV GTS LS3

  2. #2
    Lifetime Member Mr. P.'s Avatar
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    Yes the O2's are supposed to "switch" from high to low like that when the PCM is in closed-loop operation. And it takes a few seconds from startup before they begin to work (you can see that in the log). Separate question, why is your MAP sensor only reading 94 kPa at WOT? It should theoretically be 100 kPa at WOT - possibly a dirty air cleaner or other air restriction before the intake manifold?

    - Steve.
    2003 Silverado SS, with Novi-1500 "CAI mod"
    EFILive V 7.5 COS-3 (OLSD, for now!)

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    Member scottcmb's Avatar
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    Quote Originally Posted by Mr. P. View Post
    Yes the O2's are supposed to "switch" from high to low like that when the PCM is in closed-loop operation. And it takes a few seconds from startup before they begin to work (you can see that in the log). Separate question, why is your MAP sensor only reading 94 kPa at WOT? It should theoretically be 100 kPa at WOT - possibly a dirty air cleaner or other air restriction before the intake manifold?

    - Steve.
    Thanks steve.......where i live we are about 1200 feet above sea level.....always get low readings here.....my LS3 also shows low static readings.......the best i have ever seen it here was 98 on a good day.......when i go on a drive to the coast and do some logging at the same time.....when at sea level i get the 100kpa readings.....that way i gauged that my map sensors are ok and also the intake track is ok too .

    But granted i do agree with you on the intake of the blazer being restrictive with flow to the manifold when at revs. We have not long got this vehicle and i will be making up a cold air intake for this animal. I have already taken out the restrictor cup in the throttle body and de catted the exhaust. When im done im going to have to study up on how to tune this LS1B. Im use to only tuning E38's and see that this is similar to tuning but not the same

    Scotty
    2008 HSV GTS LS3

  4. #4
    Joe (Moderator) joecar's Avatar
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    Looks normal; there's a little difference between the two banks.
    Last edited by joecar; January 14th, 2013 at 08:46 AM.

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    Scott, look at the Calc.VET for getting the VE and MAF tables dialed in. With a WBO2, it works really slick, 1 good datalog and you have the VE and MAF tables 98-99%.
    ~Erik~
    2013 Sonic RS Manual - 1.4L I4T E78, tuned, turbo mods, etc.
    2008 TrailBlazer SS 3SS AWD Summit White - LS2 E67/T42, bolt ons, suspension, etc.
    2002 Chevy TrailBlazer LT 4X4 Summit White - 4.2L I6 P10, lifted, wheels, etc.

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    Member scottcmb's Avatar
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    Quote Originally Posted by ScarabEpic22 View Post
    Scott, look at the Calc.VET for getting the VE and MAF tables dialed in. With a WBO2, it works really slick, 1 good datalog and you have the VE and MAF tables 98-99%.
    Cheers Scarab....that was my next thing to do on the list.......wire up the wideband and start logging............just wanted to get your guys opinion on the the state of my NB o2's before anything else ....will be interesting to see what the economy will be like after tuning this animal.......my wife is complaining that its RATHER thirsty...lol

    Cheers Scotty
    2008 HSV GTS LS3

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    Quote Originally Posted by scottcmb View Post
    Cheers Scarab....that was my next thing to do on the list.......wire up the wideband and start logging............just wanted to get your guys opinion on the the state of my NB o2's before anything else ....will be interesting to see what the economy will be like after tuning this animal.......my wife is complaining that its RATHER thirsty...lol

    Cheers Scotty
    Sure thing, and dont get your hopes up. My parents had a 96 Jimmy with the 4.3 and it was pretty thirsty as well. Our 02 TrailBlazer with the 4.2L I6 was only ~1mpg better, but has 80hp and 25tq more.

    Clean up the VE and MAF, probably good for 1mpg. But, the shift points and midrange power usually makes it worth it.
    ~Erik~
    2013 Sonic RS Manual - 1.4L I4T E78, tuned, turbo mods, etc.
    2008 TrailBlazer SS 3SS AWD Summit White - LS2 E67/T42, bolt ons, suspension, etc.
    2002 Chevy TrailBlazer LT 4X4 Summit White - 4.2L I6 P10, lifted, wheels, etc.

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    Lifetime Member Boost's Avatar
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    Erik those are super impressive power results with the I6! Yeah, all the 'Blazers' are thirsty.
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    Member scottcmb's Avatar
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    Quote Originally Posted by Boost View Post
    Erik those are super impressive power results with the I6! Yeah, all the 'Blazers' are thirsty.
    Hmmmmm..........i wonder if an LS1 will drop into it easily???
    2008 HSV GTS LS3

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    Quote Originally Posted by Boost View Post
    Erik those are super impressive power results with the I6! Yeah, all the 'Blazers' are thirsty.
    Well not that impressive lol, the 4.3 in the Blazers are rated at 190hp/250tq and the 4.2L I6 started off at 270/270 for 02 and only went up from there (head redesign in 06 added ~15hp too). Only about 10-15hp is in the tune on premium (91+ octane), the stock spark map knocks on 87!

    Quote Originally Posted by scottcmb View Post
    Hmmmmm..........i wonder if an LS1 will drop into it easily???
    It will... You already have the LS1B PCM, swap engines and full flash a fullsize OS (I think there's a certain one floating around that has 4LO intact). Done.
    ~Erik~
    2013 Sonic RS Manual - 1.4L I4T E78, tuned, turbo mods, etc.
    2008 TrailBlazer SS 3SS AWD Summit White - LS2 E67/T42, bolt ons, suspension, etc.
    2002 Chevy TrailBlazer LT 4X4 Summit White - 4.2L I6 P10, lifted, wheels, etc.

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