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NA 98 V70 P0300, P0301, P0302, etc V70-XC70

I recently started getting P0300, P0301 thru 5, but not always misfires on all cylinders. (Each time they are set, I clear them, so I have 4 sets of codes) No other codes have been set, only P030x cylinder misfires. Starts with a sudden loss of power on acceleration, after driving maybe 3 to 7 miles. If I try to accelerate too much, the engine starts to die, but usually recovers as a let off the gas, with enough power to limp home. Last time P030x codes were set for all cylinders except #3. Once it died completely and couldn't be restarted until the next morning. Today, revving above 2k rpm would cause the engine to start dying. No popping, sputtering or backfiring is occurring, just loss of power.

Last winter, the fuel filter, vacuum lines, and MAF sensor were replaced and throttle body was cleaned as a result of various "lean" codes and stalling. Until recently ,the car was running fine.

I checked the distributor cap, wires, coil- all have about 50k miles, and tested the cam position sensor, and all looked good, though the problem is intermittent. When it's dark outside, I notice a faint glow on either side of the coil when the engine is under a load at idle, but I think this may be normal.

Is this misfire code always related to a ignition problem, or can it be related to a lack of fuel supply? Any suggestions would be greatly appreciated.

Thanks,
Kcarl








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    NA 98 V70 P0300, P0301, P0302, etc V70-XC70

    Normally, misfires such as yours happens as a result of unmetered air entering the intake manifold - vacuum leak. A leak causes a lean condition and the ECU 'fixes' it by enriching the mixture. Unfortunately, if it is too rich, the plugs get fouled and you begin misfiring until the engine dies due to flooding.

    Klaus
    --
    Did you do your Random Act of Kindness today?








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      Spoke too soon - another problem V70-XC70

      I guess I spoke too soon. The car ran great yesterday after sealing the vacuum leaks. After it warmed up this morning, it idled great but wouldn't accelerate, just bogs down. Fuel pressure stays at a steady 42 psi.

      Although I replaced the MAF sensor this past winter , I decided to disconnect it and see how the engine runs. Turns out it accelerates fine with the MAF disconnected and idles well too. Hook the MAF back up and it won't accelerate but idles fine. Does this mean the MAF is bad, or is disconnecting it taking another cause out of the picture?

      The car has not set any codes, since I sealed all the vacuum leaks found yesterday.

      Thanks,
      Kcarl








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        Problem solved. V70-XC70

        Looks like the MAF sensor was the other culprit. Replaced it, and the car has run flawlessly for a couple of days.. Has great pep and acceleration - can't remember the last time it ran this well. Hopefully it will continue this way for a while.








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          Problem solved. V70-XC70

          Do you by chance have a K&N air filter? Some of the clean&oil filters will have too much oil and coat the MAF causing premature failure.

          If not, the replacment MAF was defective.

          Klaus
          --
          Did you do your Random Act of Kindness today?








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            Problem solved. V70-XC70

            No K&N. I use the stock filter for the reason you just mentioned.

            One other question I have is that, as I was replacing the air box, I found a large, thick gasket lying beneath where the air box mounts and can't figure out what the heck it goes to. It's rubber, 3-1/8" in diameter and slightly less than 1/4" thick. I'm assuming it's from the air box or air inlet hose. I've had this thing apart many times, but just don't remember seeing this gasket before. Hopefully I loaded the image.

            thanks,
            kcarl









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      Vacuum leaks found V70-XC70

      Yep. You were right. I made a smoke tester out a coffee can, tubing and smoke bombs and found vacuum leaks that I would have sworn didn't exist. Put the car back together, and it runs great.

      To make the smoke tester, I just cut a hole in the plastic top of a large metal coffee can and glued tubing to it. I attached the other end of the tubing to a small intake inlet pipe. 'Tossed a lit smoke bomb (small, N.C. legal type) into the can and put the cover on. The expanding gases pushed the smoke though the tubing and out through the leaks. Orange smoke bombs worked great, but use small ones. Even those will pop the top off the can.

      Thanks again for the help Klaus.








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      NA 98 V70 P0300, P0301, P0302, etc V70-XC70

      Thanks for the reply. So far I haven't found any intake leaks, but I haven't made it to the hose on the fuel pressure regulator yet. It may be time to finally build a smoke tester. Does the engine sense a lean mixture through the O2 sensor, which tells the ECU to richen the mixture? How does it know which cylinder has misfired? It idles pretty well, just doesn't like it when I give it gas. Of course, it will shut down if I keep giving it throttle. I managed to limp home yesterday running 20 to 35 mph.

      Thanks
      kcarl







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