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Bad MPG, Changing O2's help!

This is a discussion on Bad MPG, Changing O2's help! within the General Help forums, part of the LSx Technical Help Section category; I have a 99' Trans Am, A4, and i get horrible gas mileage, probably 150 to a tank city driving. ...

  1. #1
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    Blue/Green Chameleon
    1999 Firebird

    Bad MPG, Changing O2's help!

    I have a 99' Trans Am, A4, and i get horrible gas mileage, probably 150 to a tank city driving. I have done everything people have mentioned, except changing my O2's. Now few questions. Would they be makin my engine light come on if they were bad, or no? Also whats the process to change them out? Thanks for any help

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    Senior Member Wheeler99WS6's Avatar
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    black, 05 Roush
    black, 99 T/A WS.6

    changing the o2 sensors is no sweat. they just unscrew. Are you still running Cats.? If so maybe you have a bad Cat. They can throw a code (engine light) but I have heard of guys having problems and not getting a code also. What mods do you have so I can better help you diagnose your problem.
    1999 T/A WS6 Black -------SOLD
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    Blue/Green Chameleon
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    Yeah im still runnin cats, damn CA emissions. Is there anyway to tell a bad cat? my mods are only SLP Lid and a cutout thats open full-time.

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    Member Tracker9118's Avatar
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    By the way you have 4 O2s on the car & a bad cat will smell like rotton eggs.

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    Blue/Green Chameleon
    1999 Firebird

    oh well than no bad cat for me, exhaust smells fine

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    Member Tracker9118's Avatar
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    You will also have power loss & your fuel mi, will go to shit.

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    Member Tracker9118's Avatar
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    When was the last time you put plugs in it????????????

    A GOOD SET.
    Last edited by Tracker9118; 01-27-2008 at 11:54 AM. Reason: Update

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    well i bought the car with 80,000 miles on it, and i looked and saw MSD wires, so i figured that they had just been changed before i got it. Dont know why someone would change wires but not plugs?

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    Senior Member SeVeReDiStOrTiOn's Avatar
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    Quote Originally Posted by airmaxon1 View Post
    I have a 99' Trans Am, A4, and i get horrible gas mileage, probably 150 to a tank city driving. I have done everything people have mentioned, except changing my O2's. Now few questions. Would they be makin my engine light come on if they were bad, or no? Also whats the process to change them out? Thanks for any help
    You can also try cleaning the front o2's first before replacing them...it's the cheaper option. CRC makes a non-residue eletrical cleaner and that's what I use.

    Also driving habits are the main cause of bad mpg....try to keep it under 2000rpms in town. In traffic I leave more room between the car in front and meso that I can do a slow rolling cruise instead of the constant stop and go....it really helps.

  10. #10
    Member 180ls1's Avatar
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    Quote Originally Posted by airmaxon1 View Post
    well i bought the car with 80,000 miles on it, and i looked and saw MSD wires, so i figured that they had just been changed before i got it. Dont know why someone would change wires but not plugs?
    pull only the easiest plugs to get to and do your best to get a judgement from those. there is a good chance there is bad plugs though thay are somewhat hard to change in our cars. But for mpg i would do o2's, clean maf, seafoam it, and new plugs. Is your engine throwing a code???

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    Blue/Green Chameleon
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    Quote Originally Posted by 180ls1 View Post
    pull only the easiest plugs to get to and do your best to get a judgement from those. there is a good chance there is bad plugs though thay are somewhat hard to change in our cars. But for mpg i would do o2's, clean maf, seafoam it, and new plugs. Is your engine throwing a code???
    dont have a scanner to check out the codes, just seafoamed it yesterday, few nice big puffs of smoke ill have to check on those plugs tomorrow and see how they are. hoping that seafoam will do some magic without havin to do anything else

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    Your dealership guy konigandy6's Avatar
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    Simple maintenance may help

    Fuel filter
    Air filter
    Fuel injection cleaning
    Plugs and tune up

    Also, I have heard keeping your foot out of the accelerator helps a lot too...

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