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engine runs horrible under2750 rpms and great above, stalls in gear S70 1998

posted by  someone claiming to be rusty shakelford on  Thu May 3 09:23 CST 2007 [RELATED]

I have a 1998 s70 5cly. turbo with an auto trans. The car will fire up and idle but idles kinda rough and will stall when i put it in gear but i can rev up the engine and it will stumble very bad until it gets to about 2750 rpm the it runs perfect and sounds excellent. i am scanning the codes with a generic obd2 scanner and i get a p0235 code which the book says is a crankshaft position sensor. So ive changed the crank position and the cam position sensors and it still runs the same. any help is much appreciated








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    engine runs horrible under2750 rpms and great above, stalls in gear S70 1998

    posted by  someone claiming to be Tapsa on  Thu May 3 18:34 CST 2007 [RELATED]

    Hi, after you propably have checked the carburator, IAC and vacum hoses I still have two more to look after as experienced in my 850 -94 N/A.
    - air inlet manifold gasget leaking
    -variable air inlet control clap valve and its vacum control

    br Tapsa








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    engine runs horrible under2750 rpms and great above, stalls in gear S70 1998

    posted by  someone claiming to be ksg on  Thu May 3 09:46 CST 2007 [RELATED]

    Please give more info - does it matter if engine is warmed up or cold, is the exhaust smoky and what color if so, did the problem start suddenly, is it associated with anything, such as previous service done on the car, is routine maintenance such as ignition, air and fuel filters up to date, any peculiar electrical symptoms on the car, is transmission shifting ok if you get under way?








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      engine runs horrible under2750 rpms and great above, stalls in gear S70 1998

      posted by  rusty shakelford on  Thu May 3 10:02 CST 2007
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      last visit: Sun May 13 03:41 CST 2007
      [RELATED]

      Sorry for the lack of information. It does not matter if the engine is warm or cold and the engine dosent smoke at all. Im not sure about the fuel filter but the airfilter is clean. I cant get the car to drive as it will stall with any load. Everything thing seems to be working fine the engine fires up as soon as i turn the key and idles at about 1200 then slowly drops to 800 or so it just seems to be missing but i can rev it up and its like a switch is flipped at 2750rpm and the engine sounds and runs perfect. i can hold the rpm above the 2750 and slowly let it down and at 2750 it seems to start missing very bad. Now for the fun part i recently purchased this engine and put it in the car cause the other one was overheated and ruined. I just cant figure out what sensor would control the engine below 2750 but not above. Is it maybe turbo related. i bought the engine from a jumk yard and it ran when pulled and was complete with intake throttle body injectors exhaust manifold and turbo and all sensors. the timing belt has not ben removed and all the wiring looks good. i wish i could drive it but it runs way to rough to try and drive. thanks rusty








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        engine runs horrible under2750 rpms and great above, stalls in gear S70 1998

        posted by  will rehsper on  Mon May 7 04:52 CST 2007
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        last visit: Tue Jul 3 14:55 CST 2012
        [RELATED]

        Check fuel pressure. My vote is for the fuel pressure regulator or maybe just a clogged filter. Vacuum line on the FPR hooked up?

        Good luck,
        Will








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          engine runs horrible under2750 rpms and great above, stalls in gear S70 1998

          posted by  rusty shakelford on  Mon May 7 09:30 CST 2007
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          last visit: Sun May 13 03:41 CST 2007
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          I havent been able to check the fuel pressure i need to get an adapter down to the small size fitting on the fuel rail. What should the fuel pressure be at the check valve? ive got the vacuum line connected on the regulator but am looking for a good vacuum diagram to make sure ive got it connected properly. i'll change the filter this week some time im still wondering why i would have the 335 code though thanks for the advice and please keep it coming








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            engine runs horrible under 2750 rpms and great above, stalls in gear S70 1998

            posted by  will rehsper on  Tue May 8 05:14 CST 2007
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            last visit: Tue Jul 3 14:55 CST 2012
            [RELATED]

            I've not come across a fuel pressure spec, just volume per minute. I think mine was somewhere in the region of 30-40PSI. Besides good (high enough) pressure, the important part is that the pressure is stable. I have a feeling your FPR isn't always doing its job to regulate the pressure.

            --Will
            850 / Mini








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        engine runs horrible under2750 rpms and great above, stalls in gear S70 1998

        posted by  someone claiming to be ksg on  Thu May 3 11:17 CST 2007 [RELATED]

        Closest I've ever had to something like this on a car was with a big cut in a vacuum hose like the hoses to the idle air control motor, brake booster, etc, (or one end of a hose falling off). If there's a crack somewhere, is it shifting and opening and closing as the engine is revved (due to some movement of the engine on its mounts)?

        I guess I would check manifold vacuum & fuel pressure if you can. If you still have parts from the ruined engine - may be worth swapping the old MAF sensor in.

        Seems like the fuel mixture must be very lean.







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