Rough running 3200

Discussion in '308/328' started by fdekeu, Sep 9, 2009.

  1. fdekeu

    fdekeu Formula Junior
    Silver Subscribed

    Jun 19, 2008
    Full Name:
    My engine does not run smooth in the 2500-3000rpm range, also idle is not perfect
    Specially in fifth gear it is most noticable
    Apart from that it is pulling strong up to the redline

    I have checked the ignition, this looks Ok, plugs and rotor arms have been replaced

    Now I am in the process of checking if there are leaks in the inlet manifold
    I have disconnected the brake servo tube and am blowing air in the manifold there
    Have only tried blowing air myself but there is not a lot of pressure build up
    I wonder how much pressure I can/must apply before I will use the compressor

    If there are no leaks I will check the valves
    There were done 5000kms/15yrs ago before I bought the car

    Thanks for responding
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  3. fdekeu

    fdekeu Formula Junior
    Silver Subscribed

    Jun 19, 2008
    Full Name:
    I have used a compressor to blow air in the manifold
    Turns out there is no pressure buildup
    No idea where it is going to
    Will try to find out in the weekend

    Can it be the air is escaping through the exhaust because there is valve opening overlap
    Can be the intake but the throttle valve and the CIS air flow sensor plate are closed
    This should restrict the flow

  4. fastradio

    fastradio F1 Rookie
    Professional Ferrari Technician BANNED

    Apr 26, 2006
    New England
    Full Name:
    David Feinberg
    OK, let's start with the basics:

    Rough idle
    Rougness in the 2500-3000 RPM range
    Lack of power under load in 5th

    And it's pulling stong??? OK

    Personally, I'd visually and electircally inspect both the plug wires and spark plug extenders. These are high failure rate components and a well-known, well-documented source of many, many...and many issues such as what you describe.

    In terms of "blowing compressed air into the intake manifold to determine ??? (vacuum leaks???), this is not a valid, or viable test, as at any given point in time, multiple intake valves will be open.

    If the ignition components prove to be good, then have the injectors "pop tested" and then go from there...


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