when i turn off my car it keeps sputtering

Slant 6 Engines

  1. Sick_Six225

    Sick_Six225 72 Dodge Dart Swinger

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    72 Dodge Dart Swinger, 3.7 225 Inline 6. When I turn off my car after driving for a little it sputters when I turn it off. How do I fix this and will this in the long run hurt my vehicle. thanks
     
  2. 63VALIANT*KISS

    63VALIANT*KISS Well-Known Member

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    its called dieseling I don't think it hurts the car mine does it once in awhile also
     
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    • Sick_Six225

      Sick_Six225 72 Dodge Dart Swinger

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      When I drive the car it drives great no problems (of course after warming up) but as soon as a turn it off it sputters just for a second. Then when I start it back up no problems.
       
    • '73red-duster

      '73red-duster FABO Gold Member FABO Gold Member

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      Check the timing.
       
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      • Sick_Six225

        Sick_Six225 72 Dodge Dart Swinger

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        Checked the timing it is on the dot, no problems there.
         
      • 67Dart273

        67Dart273 Well-Known Member

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        What does "on the dot" mean? These cars were not specified "for optimum drivability," they were spec'd for emissions, and many ran very retarded.

        Bumping the timing as advanced as it will run without other problems will help the run-on problem

        Other causes are running way too hot, carb out of adjustment, and as mentioned retarded timing. Obviously, local OD weather conditions affects the problem.
         
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        • OldmanRick

          OldmanRick Well-Known Member

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          A high idle can cause it also. I don't know if it's possible to have manifold vacuum to the distributor vacuum advance on a slant, i'm not familiar enough with them, but that can add to it. You can always shut it off in gear. I've had a few built up high idle cars that I had to do that way.
           
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          • Sick_Six225

            Sick_Six225 72 Dodge Dart Swinger

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            Carb is adjusted, it’s not running hot at all and with the timing what do you recommend. Again the car is running smooth with no issues besides when turning it off.
             
          • Abodybomber

            Abodybomber Breaking street machines , since 1983.....:) Legendary Member

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            Above POST,more than agreed.....
             
          • Sick_Six225

            Sick_Six225 72 Dodge Dart Swinger

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            The idle might be it, I need to get a Tach so I can make sure that the idle is were it needs to be at. Or is there another way I can find out were my idle is at?
             
          • Abodybomber

            Abodybomber Breaking street machines , since 1983.....:) Legendary Member

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            A tach ,recommended.If you have a vacuum gauge,find peak vacuum.:in drive. Back the idle speed ,to where you need.
             
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            • Sick_Six225

              Sick_Six225 72 Dodge Dart Swinger

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              Ok I do have a vacuum gauge so I will go ahead and try that
               
            • OldmanRick

              OldmanRick Well-Known Member

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              When "bomber" says find peak vacuum, he's speaking of setting the idle mixture screw.........After that, lower the idle speed screw to a acceptable level.

              Let us know how it goes.
               
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              • BillGrissom

                BillGrissom Well-Known Member

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                Look for a tach/dwell meter at garage sales. Many out there, and of no use on cars 1990+. Same for a timing light. Several things can make it "run on" or "diesel". One is carbon deposits on the head from running too rich at low speeds. Some say an "Italian tune-up" like running full throttle up hills can burn it off. Aren't you near the edge of the Cumberland Plateau for that?

                A throttle too far open at idle is another. There were carbs in the late 70's thru 80's with "anti-diesel" solenoids which shut the throttle tightly to stop run on. I think they needed them then because of the emissions controls and settings they added that messed up a smooth idle and required the throttle be more open at idle. Thus, anything you can do to get a better idle and allow you to set the idle throttle more closed will help.
                 
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                • Sick_Six225

                  Sick_Six225 72 Dodge Dart Swinger

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                  Thank you guys for the help, I will keep you updated.
                   
                • adriver

                  adriver Blazing Apostle

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                  Leave it in gear when you turn it off.
                  Problem solved. Sort of
                   
                • WRB426

                  WRB426 Insane 4 Mopars FABO Gold Member

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                  Maybe your car wants to keep cruising. LOL
                  But above posts should solve your problems.
                   
                • crackedback

                  crackedback FABO Gold Member FABO Gold Member

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                  Not enough initial timing!!!!
                   
                • RustyRatRod

                  RustyRatRod 30 Degrees Outta Whack FABO Gold Member

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                  Usually the cause of engine run on is something that attributes to too high an idle speed. Also, it can be detrimental to the engine. When an engine runs on, it is usually running backwards. The initial shock has broken or stripped many a timing chain.
                   
                • crackedback

                  crackedback FABO Gold Member FABO Gold Member

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                  It's not too high of an idle speed generally speaking, it's throttle blades too far open to maintain a desired idle speed, usually in gear. The drop from park to ingear is likely higher than normal.

                  Plenty of ways to tune a car, some better than others.

                  I'm out.
                   
                • 67Dart273

                  67Dart273 Well-Known Member

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                  LOL what I was trying to get at, and the OP still has not acknowledged what "on the dot" is
                   
                • 805moparkid

                  805moparkid SS And AFX Worker Bee

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                  1. 3/8 spacer below the carb, do you have one?
                  2. fuel line mod, have you done it?
                  3. idle rpm?
                  4. Timing curve? 12 initial, 30 total around 2500rpm, 45 with vac advance is a good start
                   
                • DaveBonds

                  DaveBonds Garage Trash

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                  "the dot" may also be off.

                  If you want it timed right, use a cylinder stop and find actual TDC, get some cleaner on the balancer/ damper and throw some timing tape on it, hit it with as much initial advance as your fuel can handle and worry about the rest of the total timing if you decide to blueprint the distributor spring and weight stop (advance curve) and cap phasing. Initial timing is more important than total on a driver.
                   
                • Otateral

                  Otateral Well-Known Member

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                  Not to hijack this thread, but would having timing set at 5BTDC or 10BTDC be more likely to cause this? I was running it at 10BTDC and had dieseling. It was also idling at around 850rpm. I changed timing to 5BTDC and also lowered idle to 750rpm. Not sure if what I did was correct, or if I should have left timing at 10. I wasn't getting any pinging at 10.
                   
                • BillGrissom

                  BillGrissom Well-Known Member

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                  Otateral,
                  Read my post and others above. The more you can lower the idle speed, and thus close the resting throttle position more, the better it stops dieseling by choking off the air. The more advanced you set your spark timing, the better your mileage and performance, until you reach the knock limit, which depends on many things - gas used, air temperature, etc. Modern cars use a knock sensor and the spark controller keeps advancing timing until it knocks.
                   
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