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Looking for theories on a miss

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  • Looking for theories on a miss

    Looking for a few theories on a miss my car has developed. I drove it yesterday and it started out running fine, but the time I got to work (maybe a 20 minute drive) it felt like it wasn't running quite as good as normal. But it wasn't bad at, just like maybe I needed to check my floats or something, that sort of thing. When I left work later that day, it was noticeably running a little rough, and by the time I got home it had really developed quite a miss. Almost as bad as being down a cylinder but not quite that rough. Sluggish acceleration and a pretty noticeable shake even at idle. It definitely feels like a ignition problem as opposed to fuel. It felt like the timing had slipped and the first thing I did was turn my distributor advanced and retarded, but the shake and rough idle were still there in both directions. I checked all my spark plug wires and they all look good (no damage from the headers) and are all connected. Now, here's what I've done to the car over the past few months. New MSD distributor, but my coil and control box are used items (MSD 6AL). New spark plug wires, but the plugs are maybe two years old at this point. My initial theories are maybe one of the plugs is going bad even though they're somewhat new. I did struggle for a while to get the timing set right (at one point I even had the distributor in 180 degrees off) so I'm wondering if maybe the extra strain on the plugs during that trial-and-error period was too much. I'm going to put new plugs in it this weekend and see if that helps, but if it doesn't my next guess would be either that second-hand coil or control box crapping out on me. Could either of those thinsg slowly go bad over the course of an hour, or would they just suddenly die?
    Thanks in advance!
    Wade
    '67 A-code Fastback

    "Sunlight on chrome
    The blur of the landscape
    Every nerve aware"

    http://mustangsandmore.com/memberpages2/wadeb3.html

  • #2
    Yes sir it is possible that the 6/al could be going away and you could just have a bad plug or two are they autolite.I know I had a few problem with the AR brand of autolite plugs now I'm with NGK and the plugs are firing really good.
    1984 Thunderbird svo v-6 10.088 131.67 mph
    1972 mustang coupe nhra stock eliminator 351c ho
    NEVER HAVE SO FEW OWED SO MUCH TOO SO MANY

    Comment


    • #3
      Yeah, I've got Autolites in there right now. I'll throw some new plugs at it tonight and if that doesn't help I might see if I can track down a buddy's control box and do a swap just to see. Thanks for the reply!
      Wade
      '67 A-code Fastback

      "Sunlight on chrome
      The blur of the landscape
      Every nerve aware"

      http://mustangsandmore.com/memberpages2/wadeb3.html

      Comment


      • #4
        Could be a head gasket leak, letting water in fouling the plug. I've never had a plug "go bad", but have had them fouled out. I guess anything is possible. I've heard the new MSD stuff is made in Mexico, and there have been some quality control issues, especially the dist caps. I would think if it was the box or coil, it would affect all cylinders?
        ----1999 F150 XLT Lariat Super Cab 4X4 5.4----
        -----1947 Lincoln Zephyr Coupe 5.0-----
        -----2005 Expedition Eddie Bauer 5.4----
        " Sometimes you fix the car, sometimes the car fixes you" Steve L.

        "Do not let anyone tell you it cannot be done. No challenge can match the heart and fight and spirit of America". President Donald J. Trump

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        • #5
          Guys, before you go swapping ignition boxes and pulling off heads, how about a little diagnosis first?

          What did your timing light tell you when you checked it? What about the vacuum gauge? Did you do a cylinder balance check to try to isolate the miss? No need for major surgery if you have a bad spark plug wire or a carbon track in your distributor cap.
          '70 Mach 1 - '72 Sprint - '94 F-150 XL -'97 E-150 - '05 Sable LS
          My Mach's restoration progress
          My Sprint's restoration progress
          I wish Americans wouldn't take advice on complex social issues from people that make their living from the talents they learned in kindergarten; singing, dancing, coloring, playing pretend, tossing balls, telling jokes...
          Pay attention to the people who think and highlight honesty.

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          • #6
            He wanted theories, that's why I gave some possibilities, hard to tell without being there. I would do the simple things first, dist cap, wires, etc, before I got to tearing stuff apart.
            ----1999 F150 XLT Lariat Super Cab 4X4 5.4----
            -----1947 Lincoln Zephyr Coupe 5.0-----
            -----2005 Expedition Eddie Bauer 5.4----
            " Sometimes you fix the car, sometimes the car fixes you" Steve L.

            "Do not let anyone tell you it cannot be done. No challenge can match the heart and fight and spirit of America". President Donald J. Trump

            Comment


            • #7
              Thanks for the replies, everybody! Apologies for taking so long to get back, super busy weekend. I haven't had a good chance to fully diagnose yet. I just wanted to check back and say thanks for the ideas. I'll update when I know more!
              Wade
              '67 A-code Fastback

              "Sunlight on chrome
              The blur of the landscape
              Every nerve aware"

              http://mustangsandmore.com/memberpages2/wadeb3.html

              Comment


              • #8
                Quick update: I can't find anything wrong at all with the electrical/timing so I did the old screwdriver-as-stethoscope trick and heard a slight ticking on my driver's side bank. I pulled the valve cover and nothing screwy jumped out at me by rotating the engine by hand. I pulled the pushrods and they all were straight, so I put it all back together and cranked it back up, not the ticking is loud enough that I can hear it outside the engine. So I'm thinking I've got a bad lifter. I had a lifter go down on me a couple of years ago after the car was parked for a few months during a transmission swap project but it pumped back up after a little bit of run time. Maybe that lifter finally gave out, or maybe another one. Anyhow, I think my next step will be to pull the intake and look at the lifters. Which sucks, because I just had my intake off a couple of months ago. Oh well, them's the breaks.
                Thanks for all the replies and tips!
                Wade
                '67 A-code Fastback

                "Sunlight on chrome
                The blur of the landscape
                Every nerve aware"

                http://mustangsandmore.com/memberpages2/wadeb3.html

                Comment


                • #9
                  Usually when a lifter collapses it's pretty loud.I doubt that's it. Leave the intake on and put a VACUUM GAUGE on the engine. It will tell you more than taking parts off and looking at them.If you still think it's a lifter,try pushing down on the back side (pushrod side) of the rocker with the engine running.You should be able to collapse the lifter and then allow it to pump back up.From what you described, I wouldn't be surprised if the choke closed or a power valve is leaking.Pull the plugs and check for color ,then choke operation and wiring,if the plugs look black put a power valve in the carb and try it again.Start with the basics,check and set timing,vacuum leaks and idle mixture settings.Ohm check the coil wire.

                  Comment


                  • #10
                    Thanks, Mark!
                    Wade
                    '67 A-code Fastback

                    "Sunlight on chrome
                    The blur of the landscape
                    Every nerve aware"

                    http://mustangsandmore.com/memberpages2/wadeb3.html

                    Comment


                    • #11
                      Don't think you lost a cam lobe do you? I've heard of a lot of that since they took the zinc out of the oils.
                      ----1999 F150 XLT Lariat Super Cab 4X4 5.4----
                      -----1947 Lincoln Zephyr Coupe 5.0-----
                      -----2005 Expedition Eddie Bauer 5.4----
                      " Sometimes you fix the car, sometimes the car fixes you" Steve L.

                      "Do not let anyone tell you it cannot be done. No challenge can match the heart and fight and spirit of America". President Donald J. Trump

                      Comment


                      • #12
                        I did think about that but it really went away over the course of one day of driving. It ran just fine on my way in to work that morning, and then was running like crap on my way home that evening.
                        Wade
                        '67 A-code Fastback

                        "Sunlight on chrome
                        The blur of the landscape
                        Every nerve aware"

                        http://mustangsandmore.com/memberpages2/wadeb3.html

                        Comment


                        • #13
                          I'm planning on checking my lifters this weekend, I'll report back then. It's knocking pretty loud since I put my rocker arms back on, whereas before it was just ticking.
                          Wade
                          '67 A-code Fastback

                          "Sunlight on chrome
                          The blur of the landscape
                          Every nerve aware"

                          http://mustangsandmore.com/memberpages2/wadeb3.html

                          Comment


                          • #14
                            wadeb3,

                            A few questions for you:
                            1) Is your engine "fairly fresh" or has it got a number of miles/years on it?
                            2) Does your car ever sit for long periods, without being fully driven?
                            3) Have you ever been a little lazy/lax on oil changes? For example: Running on last year's oil, because it only had a few miles on it.
                            4) Have you yet followed the advice to hook up a vacuum gauge, and while you're at it, dial in your carburetor?

                            Lifters can fail for a number of reasons and two of them are gunk/debris clogging them and/or dried seals in them! I suggest, especially if some miles on the engine or long periods of sitting, to do a fresh oil change and substitute a quart of ATF for one of the quarts of oil and run it a few hundred miles. The extra cleansers and other chemicals in ATF can do a good job of slowly/gently dissolving gunk/debris and softening seals, etc. There are many products intended for/claiming to provide many of these functions, but I've had great results over many years of using ATF.

                            On particularly high mileage engines that typically won't consume oil until 2,000 or more miles into an oil change and then starts consuming, progressively more as the oil gets older until a change, I will throw in the ATF for the last added quart before a change.

                            I once bought a semi-high milage 73 Torino with a couple of noisy lifters. I did an oil change with a quart of ATF. Within 1,000 miles the lifters quieted down and I drove the car for 80,000pus miles and then used the engine for a cube van for another 30,000 or so, before the body rotted away.

                            Just My $.02 & Likely Worth Even Less,
                            Gene
                            To quote my big brother: "Gettin' Old Ain't For Sissies"
                            '68 coupe/5.0/T5
                            '69 F250
                            '56 Chebbie 3200 P/U
                            '03 Miata (wife's ride)

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                            • #15
                              Originally posted by wadeb3 View Post
                              I'm planning on checking my lifters this weekend, I'll report back then. It's knocking pretty loud since I put my rocker arms back on, whereas before it was just ticking.
                              if it is knocking louder since it was worked on, something may be out of adjustment.
                              34 FORD coupe...Cleveland POWERED

                              it`s nice to be important but it is more important to be nice.

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