Trick for finding cross/miss fire

Discussion in 'Other Trucks' started by dirtrider73068, Oct 25, 2017.

  1. dirtrider73068

    dirtrider73068 Senior Moderator
    Staff Member

    Jul 14, 2011
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    sales associate
    Central Oklahoma
    To start off I have a 03 bonneville, its been a great car has the gm 3.8 it did great on fuel mileage. But one time the MAF went out, would not let start unplugging it I could start and drive it, did this for a long time till I could buy the 140 dollar part. Fixed it for a bit then the check engine light would come and go stay on for a while then go off. Of course by the time I could get the code read the light goes out, finally it stayed on long enough to get it read. Had a code po172 fuel trim rich bank 1.

    So reading up on a po172 it oculd be a number of things so I checked the front 3 plugs they looked fine not black and sooty, but a good clean white ash color, and its ac delco iridium plugs, plan on changing them out the ole fashion conventional plugs. It has the orignal oem wires on it with 93k miles on it now. Drove it then it starts missing, to the point of getting a hard miss the check engine lights flashes if it misses too much, reading up on that pretty much says shut off don't drive it. I can't do that, its our main trustworthy ride so been taking it easy. But funny this start up when its cold runs great till it warms up then it goes south, and starts missing.

    Doing more research today on this po172 code and missfires, and FPR leaking, I come across a YT vid that shows using a spray bottle and misting water around the wires will see it arc or missfire. So tonight I go out of course at dark with a spray bottle in hand, start it and start spraying, and by very little seen sprak crossfire between wires. So I take this wires are going to be needing replaced, and in hopes fixes the po172 and gets rid of the miss. Another article said get a screwdriver, piece of wire, wrap wire on screwdriver other end of wire ground and put it close to wires arc will jump to find bad wires. I tried that with no luck, when i misted water the spark was so small I could barley see it in the pitch of of night.

    My truck did this not long ago, would miss about mid throttle, replaced plugs still miss, then replaced wires miss went away and hoping this is the same case. Will find out tomorrow once I get them replaced, bad part is this v6 is inverted it sits sideways in the engine bay and getting to the back wires is going to be a fight.

    SO if anybody is chasing a miss try the mist spray at night to find out if plug wires are crossfireing or miss firing.
    Kennyray, MikeG and gmctrucks like this.

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