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Hi temp, low boost? S70

Hi
I am Having problems with my 1998 S70 Turbo

At start up, when cold, it has an agressive acceleration, I can really feel the boost building up at about 3000 rpm, and BOOM!!! kicks my back to the seat.

But... few minutes later, when the car starts reaching its adecuate temp, it turns sluggish and less responsive at all RPM range, I can even hear a slightly different exhaust note. At this time, the car stills runs OK, no hesitation at all nor rough idling, but theres no more "kick my back to the seat" feeling.

I can also hear a slight hissing sound coming from inside the dash (back of the instrument cluster) but I guess if theres a vac leak there, it has nothing to do with the turbo performance. Right?

What about a clogged Cat?, though not OBDII codes thrown from the Cat Sensor.

Any hints? Thanks
--
1999 Volvo S70R








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    Hi temp, low boost? S70

    ANY vacuum leak hurts. find the leak and fix it. Does your car have a boost gauge, that is driven by a vacuum line.
    You might also check the flap at the AMM and make sure it is fuly open when the engine is warm.

    Klaus
    --
    (V♂LV♂s 1975 164, 1995 854T, 1998 V70R)








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      Hi temp, low boost? S70

      Thanks Klaus

      Just Measure boost while hot, its about 6 psi at full throtle, with pikes of 7 psi. sounds too low to me.

      What is the "flap at the AMM"? I would like to check on that but dont have any idea?


      --
      1999 Volvo S70R








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        Hi temp, low boost? S70

        Sorry, the flap is for non-turbos.

        The boost at 3000rpm/full load should be 90kPa, or about 12 pounds/inch. Vacuum pressure regulates how much boost you will get. Start checking all vacuum elbows and that "hissing" sound under the dash.

        Klaus
        --
        (V♂LV♂s 1975 164, 1995 854T, 1998 V70R)








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          Hi temp, low boost? S70

          I checked the Air Mass Meter as you suggested; I found that the clamp of plastic hose that exits the AMM was totally loose, then I cleaned the contacts at the plug, and went for a drive.

          As Usual; At start up when cold, the car was very powerful; so I kept on driving waiting for it to warm up and expecting to start loosing its boost, BUT it never happened!!!, I kept driving for almost an hour enjoying every minute, I didnt want to get out of the car!!!

          Now I dont know what does it have to do with the symptoms I described early, Do you?

          By the way, I still hear a hissing sound ( Bpsssssss...) while the turbo starts to build up its boost, Maybe thats the way it should work.

          Thank you very much.
          --
          1999 Volvo S70R








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            Hi temp, low boost? S70

            Perfect. When the engine is cold (you shouldn't use the boost until the car warms up BTW) the ECU adds more gas to the air mix. So, when it warmed up you were running too lean.
            The hissing sound is not good. Spend some time tracking that noise down, it is not normal.

            Klaus
            --
            (V♂LV♂s 1975 164, 1995 854T, 1998 V70R)








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            Hi temp, low boost? S70

            As stated on another post, there should be no hiss. You probably still do have a vacuum leak. To secure the MAF, this is recommended: http://www.volvospeed.com/Repair/maf_secure.php
            --
            1998 S70 T5 Emarald Green Metallic, 2004 V70 2.5T Ruby Red, Previous Owner of Black '94 850 Turbo Wagon. My cars have been running so well lately they've got me worried.







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