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Catalytic converter/o2 sensors and MAF issues V70-XC70 1999

posted by  someone claiming to be BoonBoon on  Mon Jun 25 16:48 CST 2007 [RELATED]

I have a 99 xc70 with CEL on. The past few days the idle has been sketchy with puffs of dark exhaust upon starting. At highway speeds it is fine but low low speed it sputters. The exhaust is real strong now. I have gotten codes ECM 280A front o2 and ECM 4801 3 way CAT. The rear o2 sensor has bee replaced twice. It is at the shop now getting ready for her appointment tommorow. I am just trying to figure out if it is purely the Cat or is the MAF involved? And how did my car get so screwed up? We have another 99 xc70 same mileage also needing a front o2 sensor. We take good care of our cars. Is this unusual? Or is the luck of draw and part and partial of owning a volvo? Klaus, what is your take. Am I way beyond the possibility of just a vaccuum leak? Help!!








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    Catalytic converter/o2 sensors and MAF issues V70-XC70 1999

    posted by  KlausC on  Tue Jun 26 07:42 CST 2007
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    last visit: Fri Oct 24 10:15 CST 2014
    [RELATED]

    When my 854T started puffing gas at startup, it was because the fuel pressure regulator died and gas was entering the intake manifold through the vacuum line.

    I seriously doubt that your O2 sensor or your CAT is bad. You may need to have your MAF cleaned, but that has it's own code if it has failed.
    Both of the O2 sensors can be checked with a very good multimeter for proper current draw. That is the only way to really determine if it is bad. Trouble codes are nice, but not definitive.

    Klaus







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      Catalytic converter/o2 sensors and MAF issues V70-XC70 1999

      posted by  someone claiming to be BoonBoon on  Thu Jun 28 15:39 CST 2007 [RELATED]

      I have been talking to two different indy volvo mechanics who both think this is the cat. Is it unreasonable for me to ask them to check/replace the vaccum lines and clean the maf prior to doing the cat. Or is this something they would do in the first place? I guess what I am asking is what steps can we take before jumping into replacing the cat and o2 sensor. A cat replacement is upwards or $1300. I have 105k mi on the car. If this is a process of elimination type thing where do I start and where do I go before I fork out the cash for the new cat? Thanks for any input.








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        When a catalytic converter dies V70-XC70 1999

        posted by  KlausC on  Thu Jun 28 17:13 CST 2007
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        last visit: Fri Oct 24 10:15 CST 2014
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        It normally crumbles into a heap and blocks the flow of exhaust, allowing the engine to idle but not accellerate. Your 2 indies are looking at a scanner and following its lead. That doesn't take any thought at all, and besides, the money they make on a new cat and O2 sensor can send them to the Bahamas for the weekend :)

        I say again, if there is black smoke comming out of the exhaust at startup, there is too much gas in the intake manifold. You are running super rich and the very nice odor coming out of the tail pipe is saying the same thing.

        One of the ways to get too much gas in the manifold is by a broken fuel pressure regulator. The gasoline gets sucked up through the vacuum line and staight into the manifold.

        MOST catalytic converters will go past 250,000 miles, so long as leaded gasoline is not added. I assume you haven't driven to Mexico and tanked up there.
        The O2 sensor may be bad, but the electrical resistance needs to be tested on both sensors.

        Use the OBDII scanner as a guide, not a bible!


        Klaus







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          When a catalytic converter dies V70-XC70 1999

          posted by  someone claiming to be BoonBoon on  Sun Jul 1 16:16 CST 2007 [RELATED]

          The idle problem continued last night with a few new clues. When the car is at speeds of 25 and above it runs seemingly fine but with an overwhelming smell of exhaust. my clothes reeked last night even with windows open. When I came to a stop, the needle was going up and down up and down AND I had to stomp on the brakes??? I got out of the car and in the dark of night could clearly see exhaust coming out. The tailpipe is covered with black dust when I rub my fingers there. I spoke with another mechanic who believed a failed cold start cellinoid was the problem which in turn affects the vaccumm hence the brake compromise.At speed it is getting air into the system. It is dumping gas prematurely into something or other? And the sut(black dust) is mucking up the o2 sensors giving off false information to the cat. That what the guy told me and it seemed to fit the bill. What do you all think of this possibility?








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            When a catalytic converter dies V70-XC70 1999

            posted by  KlausC on  Mon Jul 2 03:59 CST 2007
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            last visit: Fri Oct 24 10:15 CST 2014
            [RELATED]

            I would first look for a severe vacuum leak. You are running much too rich which is causing the O2 sensors to go nuts.
            On the passenger side of the intake manifold, there should be a vacuum elbow coming out and going under the manifold. Use a light and inspect for cracks, you could even wrap it in electrical tape, just to make sure there aren't any leaks there. Also check next to the throttle body on the other end of the manifold, there is a vacuum there which could have come loose.

            Klaus






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