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Erratic Missing & Running Lean??

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    #1

    Erratic Missing & Running Lean??

    I have a 91 gm and im having an erratic miss in one of the cylinders on the drivers side. It runs fine but you can hear it in the exhaust. Its easyest herd at about 1500rpms. i pulled all the spark plugs to look. the passenger side looks normal. but it looks as if the plugs on the drivers side have abit of exhaust buildup on them. i also noticed that the rods where at little worn in an oval shaped on the tips, and the valves looked a little white. im guessing its running lean but im not sure why. would the egr make it run lean? any input is apreciated. thanks
    Stock 91 Merc GM GS 5.0L EFI, AOD, 2.73 Open diff
    Current Best 1/4 Mile 17.175 = 165 RWHP 190 Engine HP
    http://www.supermotors.net/vehicles/registry/15193
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    #2
    does it happen on start up plus welcome to cardomain looks just like mine with out the turbines

    1989 mercury grand marquis gs / 2014 ford focus s daily driver
    302 lopo with ho upper/ aod with trans go shift kit
    k code 3:55 posi rear/big brake swap tow package car

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      #3
      A lot of the Mercs and CVs I have driven seem to miss on #7 and or 8. How did you look at the valve got a bore scope or did you pull thge head.
      Scars are tatoos of the fearless

      Comment

        #4
        Originally posted by turbo2256b
        A lot of the Mercs and CVs I have driven seem to miss on #7 and or 8.
        those two plug wires are prone to arcing more than others for some reason on our cars....
        Pete ::::>>> resident LED addict and CFI defector LED bulb replacements
        'LTD HPP' 85 Vic (my rusty baby) '06 Honda Reflex 250cc 'Baileys' 91 Vic (faded cream puff) ClifFord 'ODB' 88 P72 (SOLD) '77 LTDII (RIP)
        sigpic
        85HPP's most noteworthy mods: CFI to SEFI conversion w/HO upperstuff headers & flowmasters P71 airbox Towncar seats LED dash light-show center console w/5 gauge package LED 3rd brake light 3G alternator mini starter washer/coolant bottle upgrade Towncar power trunk pull underhood fuse/relay box 16" HPP wheels - police swaybars w/poly rubbers - budget Alpine driven 10 speaker stereo

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          #5
          Yes it does it on start up. And i have had the heads off the motor, it was rebuilt about 3 months ago. I had to change the head gaskets so i just pulled the motor and did it all. I used the old parts put a cleaned them all well b4 i put em back in. There was some buildup on the outside of the exhaust valve on #8. and like i said the rods where at little worn but the rest looked fine. This car only had 70k when i rebuilt the motor. Im running it in bracket on the weekends so i needed it to be consistant. so far its not doing to bad. its within .05 every trip down the 1/4. Im also getting .050 lights. I dont know if anyone else noticed but it you take your tps off you will run about .30 faster in the 1/4. No idea why. I found out when mine went bad.
          Stock 91 Merc GM GS 5.0L EFI, AOD, 2.73 Open diff
          Current Best 1/4 Mile 17.175 = 165 RWHP 190 Engine HP
          http://www.supermotors.net/vehicles/registry/15193

          Comment

            #6
            What tips? you mean exhaust the rear turn downs from the factory. Might be able to fix your lean cylinders. They might be oveheating a bit. One reason might be due to poor fuel distribution in the fuel rail. Havent had a chance to check that out yet.

            The cooling issue I have aa fix for I do on all my engines now be it Chevy Ford. Its easy on the FI 5.0s just a bit difficult becausee of space limits.

            Must also ask what have you done to your engine?
            Scars are tatoos of the fearless

            Comment

              #7
              I think hes talking about the TPS (sensor)
              Pete ::::>>> resident LED addict and CFI defector LED bulb replacements
              'LTD HPP' 85 Vic (my rusty baby) '06 Honda Reflex 250cc 'Baileys' 91 Vic (faded cream puff) ClifFord 'ODB' 88 P72 (SOLD) '77 LTDII (RIP)
              sigpic
              85HPP's most noteworthy mods: CFI to SEFI conversion w/HO upperstuff headers & flowmasters P71 airbox Towncar seats LED dash light-show center console w/5 gauge package LED 3rd brake light 3G alternator mini starter washer/coolant bottle upgrade Towncar power trunk pull underhood fuse/relay box 16" HPP wheels - police swaybars w/poly rubbers - budget Alpine driven 10 speaker stereo

              Comment

                #8
                Originally posted by 85crownHPP*
                I think hes talking about the TPS (sensor)

                I think this old farts been working to hard <
                Scars are tatoos of the fearless

                Comment

                  #9
                  Maybe the injector on that cyl is partially clogged and starving it for fuel? Vacuum leak on that cyl from a bad gasket or leaky injector O ring?
                  86 Lincoln Town Car (Galactica).
                  5.0 HO, CompCams XE258,Scorpion 1.72 roller rockers, 3.55 K code rear, tow package, BHPerformance ported E7 heads, Tmoss Explorer intake, 65mm throttle body, Hedman 1 5/8" headers, 2.5" dual exhaust, ASP underdrive pulley

                  91 Lincoln Mark VII LSC grandpa spec white and cranberry

                  1984 Lincoln Continental TurboDiesel - rolls coal

                  Originally posted by phayzer5
                  I drive a Lincoln. I can't be bothered to shift like the peasants and rabble rousers

                  Everything looks like voodoo if you don't understand how it works

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