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rough part throttle-runnin' rich?

Discussion in 'The Garage' started by jshadwick, Jan 31, 2004.

  1. jshadwick

    jshadwick Registered Member

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    rough part throttle-runnin\' rich?

    Hi y'all,
    Keep noticing that when i push down the accelerator part way ,in park/neutral, that it starts 'lugging down', loping, missing, or something to that effect. Will almost die, but seems to keep on. At WOT (when getting on freeway, NOT in park), things seem to be ok. As a matter of fact, i dont notice this any other time besides when i part-throttle it- in park/neutral.

    Driving me nuts.

    Did the tune-up thing with new plugs, wires, cap/rotor (plugs looked good). Changed the fuel filter, pcv. Changed the ignition module (gm),and knock sensor (gm) because i got
    codes, but still does it. Changed the t-stat sensor. Had timing checked (correctly), multiple times.
    Motor is a relatively new stock gm crate motor with 20k on it. Been told that cat gets real hot-'almost glowing'. Exhaust is clean, no carbon, smoke, etc...

    The egr valve SEEMS to move ok, at least when i have pushed on the diaphragm when cold. Wondering if its the fuel pressure regulator. Just got a code 45 the other day (runnin' rich-02 sensor). Am replacing 02 sensor tomorrow, though i am not too confident that that will fix it...
    Basically, Im tired of replacin' parts and just want to get to the root of the problem, fix it, and be done with it. Whats this sound like to y'all??? Something to do with fuel system? Any ideas?
    Thank ya much,
    Jim /forums/images/graemlins/confused.gif
    '87 k5, 350 tbi, at
     
  2. jeffro

    jeffro 1/2 ton status

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    Re: rough part throttle-runnin\' rich?

    Get a miti-vac pump to test your EGR diaphragm. It might have a hole in it.
     
  3. Thunder

    Thunder 3/4 ton status

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    Re: rough part throttle-runnin\' rich?

    I dont think it is your 02 sensor. The fact that is threw a code 45 means the o2 is working. The 02 saw a rich exhaust and thru the code.
    There prolly is a problem somewhere else causing it to run rich.
    Does it run good when cold and worse as it warms up?
    If so it may be a bad coolant temp sensor. It may be tellng your ECM that the engine is cold when it is warmed up. causing the ECM to dump more fuel in than it needs.

    Could also be the throttle position sensor or MAP sensor.
    The way you describe the problem sounds like possibly MAP sensor to me. bad MAP sensor can have a OK idle but run like crap at cruise speeds.
    BUT
    TPS can also do this too.

    What other codes has it been throwing?
    Also Buying a good scanner is usually cheaper in the long run than throwing parts at it
     
  4. jshadwick

    jshadwick Registered Member

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    Re: rough part throttle-runnin\' rich?

    i took it into a shop that does smog tests. they said: vacuum leak at rear intake manifold and egr diaphragm leaking vacuum.
    so, new intake gaskets and egr. as i work full time and go to school 6 days, i have to have them do it /forums/images/graemlins/mad.gif DANG! i just had the gaskets replaced within the last year because it was leaking out the front.
     

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