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  • Need help

    I recently bought a 95 Lumina LS with the lq1. It's been having some running issues where the car will rev up to about 3k by itself and then drop down to about 600rpm and sputter or it will just die on initial start up. So I went and got it scanned (it's OBD 1.5) and it had both quad driver a & b codes come up along with an o2 sensor. So I went and bought a computer for it and put it in. I went a drove it around the block and it ran beautifully plus shifted much better for about 10 minutes and then it went back to doing what it originally was. I messed around with it some more and unplugged the MAF. It ran silky smooth. I went and bought a new MAF, installed it and it ran like hell again as soon as I fired it up (with the new MAF). So at this point I'm at a loss and need some help. I don't know if its a possible vacuum leak somewhere, if it's a wiring issue triggering the quad driver code to come up or maybe a lower intake gasket. The only other bit of knowledge I have on it is that it had about 20 codes pop up that were brake related (my guess is that is caused by a wiring issue somewhere). The brakes are very hard to press and it doesn't stop well at all especially considering the fact that it has a dual piston brake set-up. Checked the brake booster, thought that might be tied in to all this somehow but doesn't look like it. My scanner wont read this car so I'm basically just throwing parts at it blind. Any ideas out there? And sorry for the lengthy paragraph.
    -Thanks

  • #2
    Replace the bad o2 sensor. Disconnect Battery for 20 minutes and then reconnect battery.

    Bleed the brakes. You will likely find one or more of the following:
    Bad soft line(s) ~ Replace found bad part.
    Frozen/Corroded Guide Pin(s) ~ Replace found bad part.
    Bad, stuck-frozen Caliper(s) ~ Replace found bad part assembly.

    Update this thread with your end result soon after replacement of faulty equipment.
    Lifting my front wheels, one jack at a time.

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    • #3
      Considering the bad idle and hard brakes I would buy an intake manifold gasket set and change them.

      When I got my 91 many moons ago it would almost bounce off of the rev limiter on startup and would almost power through the brakes. Reason being the unchecked air introduced behind the TB, and because of this it couldn't produce any vacuum for the brake assist since the engine drawing air in against the back of the TB is what produces vacuum. Compound that on top of a very high idle and you have a car that will be hard to stop.

      This situation will also provide you with a lean condition as far as the O2 is concerned because half of the air entering the engine isn't being metered by your MAF, and your MAP can't get a good vacuum signal because of the intake gaskets leaking.

      This is just my 2 and experience and I hope this helps.

      Sent from my HTC One X using Tapatalk
      -60v6's 2nd Jon M.
      91 Black Lumina Z34-5 speed
      92 Black Lumina Z34 5 speed (getting there, slowly... follow the progress here)
      94 Red Ford Ranger 2WD-5 speed
      Originally posted by Jay Leno
      Tires are cheap clutches...

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      • #4
        a 95 actually wouldn't have a MAP sensor... it's all done through the MAF.

        it does seem like one hell of a vacuum leak to me.
        1995 Monte Carlo LS 3100, 4T60E...for now, future plans include driving it until the wheels fall off!
        Latest nAst1 files here!
        Need a wiring diagram for any GM car or truck from 82-06(and 07-08 cars)? PM me!

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        • #5
          Ok i'll check those out. Thanks you guys for your help! I appreciate it

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          • #6
            Fuel pressure regulator leaking gas into the vacuum line?
            sigpic

            "When you don't do anything, you have plenty of time to post questions that don't mean anything tomorrow."
            - Ben

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            • #7
              Finally got around to working on the car today. I replaced the upper & lower intake gaskets along with the valve cover gaskets. There was a bunch of vaccum leaks, a couple major ones and also replaced the o2 sensor. Runs beautifully now!

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              • #8
                Awesome

                Sent from my HTC One X using Tapatalk
                -60v6's 2nd Jon M.
                91 Black Lumina Z34-5 speed
                92 Black Lumina Z34 5 speed (getting there, slowly... follow the progress here)
                94 Red Ford Ranger 2WD-5 speed
                Originally posted by Jay Leno
                Tires are cheap clutches...

                Comment

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