98 eldo running lean bank 1,2
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Cadillac Seville / Cadillac Eldorado Forum Discussion, 98 eldo running lean bank 1,2 in Past Cadillac Vehicle Discussion; I pulled my codes and p0171 and p0174 showed up which are lean bank 1 and 2. Also o2 heater ...
  1. #1
    eldorado_sean's Avatar
    eldorado_sean is offline Cadillac Owners Fanatic
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    I pulled my codes and p0171 and p0174 showed up which are lean bank 1 and 2. Also o2 heater p0135. The gas is about 8 months old so could that be making it run lean? And right after I cleared it no codes came up after and the check engine light went away. We had a few codes in different sytems but they were history.
    Should I run the car until gas is used up then use 91 octane for the next fill? Thanks and what is the o2 heater?

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    Re: 98 eldo running lean bank 1,2

    Start going through Cadillac Tech Tips to find threads pertaining to diagnosis of the two codes. There are five threads currently running in here, Deville and Northstar Performance that are diagnostics and repairs for those codes.

    Lean codes are not caused by O2 sensors 99.95% of the time - it's vacuum leaks. Start snooping with the engine cover off.

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    eldorado_sean's Avatar
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    What should I do about the heated o2 sensor. I'm confused of where its located. is it after cats or manifold? is it on the far side or toward the front of the engine? Should I give it to someone else to do from the bottom if it is too difficult and what are the effects if I don't change it immediately?

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    Re: 98 eldo running lean bank 1,2

    That O2 Sensor is on the right bank (rear) manifold. Not changing it immediately won't hurt a thing. It's strictly emission related.

    Those two codes point to a vacuum leak. Check the PCV hoses.

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    Re: 98 eldo running lean bank 1,2

    Where did you get O2 sensor problems out of a pair of lean mixture codes ??????? Vacuum leak.

    Drive the car through at least a tank of fresh gas and unless you have further driveability problems leave the code scanner alone.

  7. #6
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    ....
    Quote Originally Posted by eldorado_sean
    Also o2 heater p0135.

  8. #7
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    When I pulled the codes I got the o2 heater code (current)

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    Re: 98 eldo running lean bank 1,2

    Quote Originally Posted by eldorado_sean View Post
    I pulled my codes and p0171 and p0174 showed up which are lean bank 1 and 2. Also o2 heater p0135. The gas is about 8 months old so could that be making it run lean? And right after I cleared it no codes came up after and the check engine light went away. We had a few codes in different sytems but they were history.
    Should I run the car until gas is used up then use 91 octane for the next fill? Thanks and what is the o2 heater?
    -------------------------
    Should I run the car until gas is used up
    then use 91 octane for the next fill?

    NO - fill it up NOW with 91/93 whatever you can get -
    you want to "dilute" that old gas with new ASAP -

    don't worry about the O2 sensor for now -

    P0171 and P0174 are caused by a big vacuum leak -

    easy way to locate the leak -

    get a can of carb cleaner - attach the little hose to it -

    remove the beauty cover and as much other stuff as possible
    from the top of the motor -

    start the engine - let it warm up a little - and wait until the idle speed settles -

    now - get close to the engine -
    and spray the carb cleaner near and around all vacuum hoses -
    pay particular attention to the 90* elbows of the PCV system -

    spray around the base of the intake -

    spray around the back - passengers side - of the intake -
    around the back-fire overpressure valve -

    what you are looking for is a dramatic change in the engine idle -
    when the idle increases - you found it -

  10. #9
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    Ok ill do it on Monday. But I don't think I can get a full tank of 91. Because we need new tires ASAP, need to smog and renewing registration. So will a couple gallons of 91 work? And they don't sell 93 in my part of ca

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    Re: 98 eldo running lean bank 1,2

    Quote Originally Posted by eldorado_sean View Post
    Ok ill do it on Monday. But I don't think I can get a full tank of 91. Because we need new tires ASAP, need to smog and renewing registration. So will a couple gallons of 91 work? And they don't sell 93 in my part of ca
    ----------------------------
    you will NEVER pass the smog test until you fix the vacuum leak -

    put as much fresh gas in as you can -
    the more the better - 91 - 93 - whatever -

  12. #11
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    Re: 98 eldo running lean bank 1,2

    I've been PM'd by eldorado_sean - he also went in and filled the transmission with the engine off. I'm coaching him on how to get it back down, close to the proper level.

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    Re: 98 eldo running lean bank 1,2

    FORGET THE GAS. It has nothing to do with it.

  14. #13
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    Ok so I just tried the Carb cleaner around the intake and everywhere else. Not a single thing happened. We let it rest for 10 mins and tried again.... nothing. So this isn't a vaccum leak so is it gas or something else?

  15. #14
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    If you're sure there isn't a vacuum leak, try cleaning the MAF.

  16. #15
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    Maf was clean. Were going in about 2 hours to get new tires so if codes come back. Ill post again. Thanks everybody hopefully no more codes! And filling up on 91 for a couple tanks will make sure its running like brand new!

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