Question about Chevrolet S 10

1 Answer

ON A 92 S10 BLAZER,4.3 ERRATIC IDLEAT IDLE,RPMS RAISES AND LOWERS TO ALMOST STALLING,WHEN TRYING TO THROTTLE UP,IT STARTS TO LOPE AND BACKFIRES IN INTAKE,BLACK SMOKE OUT OF THE EXHAUST, DISCONNECT HOSE FROM PCV VALVE IT WILL IDLE NORMAL,BUT WILL NOT THROTTLE UP CORRECTLY. FUEL PRESSURE IS 55PSI, EGR IS NOT STUCK OPEN,HAVE EVEN TRIED IT WITH CONNECTOR DISCONNECTED. I CAN DISCONNECT IDLE AIR CONTROL VALVE AND IT WILL IDLE FAST WITHOUT LOPING AND EVERYTHING ELSE CONNECTED BACK UP. WHAT IS GOING ON WITH THIS

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  • jeffmiller90 Feb 08, 2010

    There is hardly any air bypassing that pcv valve when putting air to it. Is it possible for the IAC valve is not working properly to allow the necessary air in that way. The pcv hose is connected passed that valve, so that is why i'm wandering about that

  • jeffmiller90 Feb 08, 2010

    That's the thing, I am not getting any fault codes out of this. If the the IAC valve is sticking in one place will that keep it from throttling up also?

  • jeffmiller90 Feb 08, 2010

    The IAC is operating,with the scanner hook up and vehicle running,it is showing everthing working,including the map sensor. it will take throttle,but lopes at first then starts to backfire,blowing black out the tailpipe.believe me,you don't need a case of bud light to get a buzz on right now. (:

  • jeffmiller90 Feb 08, 2010

    PROBLEM SOLVED.Just to let you know,I found a 1 in vacuum hose at the rear of the plenium down underneath back at the distributor split and off. put a new one on . throttles up and idles fine. thank you for your help.

  • jeffmiller90 Feb 08, 2010

    thank you for your time that you spent with me on this.

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  • Chevrolet Master
  • 19,396 Answers

Hi.

You need to replace the PCV valve, it is stuck open.

The PCV valve function is re-directing the gases from the crank case into the fair that is going to the engine.

A way to test the PCV valve is disconnecting the PCV hose , starting the engine, and with the car on idle, checking if there is suction from the hose. If there is no suction, then the hose is clogged or kinked. don't feel a vacuum you need to check the hose for clogs or other blockage.

If the hose is OK, test the valve itself by blowing air in the PCV hose. If the air blown into the hose find no resistance, then the valve is stuck open and must be replaced.

Be careful not to breath the air coming from the PCV, as the gas in there is poisonous.

If the PCV valve is OK, test the vacuum system, but it looks like the problem is PCV valve or hose.

Regards.

Posted on Feb 08, 2010

  • Ginko
    Ginko Feb 08, 2010

    A faulty IAC control valve will be the same symptoms, the trouble will be only on idle in that case.




    the IAC valve is more difficult to test. You need to remove it and check if the pin is moving freely.




    Ensure that you also have done a fault code reading, that can tell you more about the fault. A code scan can be done for free at Autozone.

  • Ginko
    Ginko Feb 08, 2010

    If the PCV valve is closed, as you say, and you do not get any code, replace the IAC valve, it is delivering air erratically when the engine is idling.


    If the problem is not only when idling , but also on driving, then things are different.

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