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91 c1500 5.7L idle ok hesitates when in R or D with brake applied

Discussion in 'GM Powertrain' started by sergeono33, Sep 16, 2012.

  1. sergeono33

    sergeono33 New Member

    hello, New to this forum. i got 91 silverado 1500 with 5.7 issue im having is the engine stumbles a little whenever it is in R or D. At idle in Park or N the engine runs smooth no signs of hesitation. No code and /or light on. First found IAC valve getting stuck replaced it. issue got better but still there. checked MAp-ok Knock sensor-ok 02 sensor-new with a nice wavefor at idle. temp sensor-new, TPS- ok smooth wake form, new plugs and cap n rotor.....
    ONe thing i notice is that when i spray brake cleanner in the intake manifold gasket area, the 02 tends to pick up that extra fuel that i'am sprying. Any ideas or commomng problems anyone has gone through?? Thank you.
  2. Pikey

    Pikey Moderator Staff Member 3 Years ROTM Winner 1000 Posts

    If you are spraying carb cleaner on the intake gasket and the rpms are going up then it sounds like you have an intake manifold leak. You just have to be sure that none of the spray from the carb cleaner is getting into the Throttle body. If you are sure that it is not, then I would definitely say you have an intake leak. That may not be causing your issue, but it is a place to start.
  3. sergeono33

    sergeono33 New Member

    Thanks for replying, yes im 100% sure the gasket is leaking and yeah im not 100% conviced that is the main issue but know i need to get rid of any air leaks first. i should have it off in the next 10 mins thanks again.
  4. Pikey

    Pikey Moderator Staff Member 3 Years ROTM Winner 1000 Posts

    Habe you checked your trans fluid? I have seen trucks with low fluid cause stalling and rough idle when put in gear.
  5. sergeono33

    sergeono33 New Member

    You know what, that never crossed my mind. Definitely will look into that. Thanks!

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