Neg % high fuel trims in idle and high rpms and eng. miss.

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  • #250782
    jesg45
    Participant

    I have a 05’Chevy Impala LS 3800 vin K. Has an engine miss and just got worsed to where it’s not safe driveable anymore. Pops code PO300 and the fuel trims are high all the time. LTFT of -20% whether at idle or at high rpms. STFT in the -3, -7%. I’ve been playing with this for over two months. I’ve have replaced a few parts already, as a matter affect, too many, not that it didn’t them, since most were O.E. All the ignition sys. is being replaced, from plugs to ICM, F/P, both O2 sensors, MAF, MAT, CKP, rbld heads, vlvs leaking, upper plenum, all new gkts, flushed all inj. and read 12 ohms. Eliminated EGR, blocked it off. Has good fuel pre. and holds with key off. Also, notice with my DVOM hooked up to battery, when running smooth for maybe 5 or 10 seconds DVOM reads 14.1 volts, but when it’s missing, reads 12.2 volts and lights dimmed. It almost seems like if I turn key off/on for a fraction of a second. Your help will be greatly appreciated. Thank you.

    #256839
    jesg45
    Participant

    on 9-3 2020 I posted a problem but, so far, I haven’t had any response. Thank you.

    #263111
    jesg45
    Participant

    Hello out there, haven’t heard from anyone, yet. Seems like no one has come across a problem like mine, yet. Maybe I confuse everyone the way I express the problem. Maybe I need to rewrite it as just one little simple problem.

    #275183
    jesg45
    Participant

    Hello, anyone. Does anyone have any idea about my veh. problem? Like to here any response, any opinions from someone else or maybe I am at the wrong page for asking for any help.

    #281287
    Fleet mechanic
    Participant

    Sounds like a vacuum leak to me.

Viewing 5 posts - 1 through 5 (of 5 total)
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