Rough Idle, Sluggish Start

Discussion in 'Technical' started by Ian240B, Jul 30, 2014.

  1. Ian240B

    Ian240B Member

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    Well, I actually have no idea. I watched a video on YouTube from Summit Racing about tuning the carb and it instructed me to plug a vacuum tester into the (I believe this is right, I'm trying hard to not sound buffoonish) vacuum manifold port. Constructively I have no idea what that does, I'm sort of just following instructions in a rote manner.

    Timing is something I've sorta suspected might be an issue but I'm trying everything I can myself before addressing it. I'll have to put her in the shop for the timing, the car doesn't seem to have the writing needed to read the timing with the light.

    The alternator and voltage regulator are both new within the year. The alternator is a 65 amp from O'Reilly's. I couldn't really find any information about whether or not there are different types of voltage regulators, so it's just the $24 deal from the parts shop. I've been toying with the idea of putting a smaller pulley on the alternator to squeeze a bit more juice from it, it really seems to be overtaxed by the fuel pump. Mostly I was wondering if the electric pump might be supplying too much fuel, if such a thing is possible.
     
  2. Pintony

    Pintony Member

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    Hello Ian204B,
    First off those pops are from a lean condition I know others have has success with removing the choke but I feel that a correct functioning choke can be as rewarding as fuel injection.
    The choke butterfly is only part of the equation. There is also the fast idle cam adjustment.
    Remember the Idle screw in the bottom flange of the Carb. is is an "AIR" adjustment. The farther out the leaner the mixture.
    Secondly... Is your fuel pump a one wire or two?
    Where is it grounded? Does your negative battery cable go from the Neg. terminal to body to engine block?
    If not? This needs to be fixed!
    From Pintony
     
  3. Pintony

    Pintony Member

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    Around 4pounds of fuel pressure is good for a carb-ed engine.
     
  4. Pintony

    Pintony Member

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    Bad ground!
     
  5. groberts101

    groberts101 Member

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    if this problem changes based on weather conditions?.. it sounds you have some tuning issues to sort out. My best quick guess is timing is off and fueling is being affected by it. As Mustangnut mentiones above.. you should be well above 15 inches unless the motor is just plain worn out.
     
  6. Ian240B

    Ian240B Member

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    I've readjusted the idle mixture using the vacuum tester to make sure I got it as good as I can. 15psi is the best I can do. I'm not familiar with the fast idle cam adjustment and google isn't helping me much, can you elaborate please?

    My idle mixture screws seem to be about the same height, one on either side of the car, right now both are set about the same distance out from the body, since the video said to adjust them the same.

    I haven't had a chance to dig around near the fuel pump, hopefully I can get that info this weekend.

    The negative (black?) battery cable goes straight to the engine and is attached via a big ol' bolt, nothing else.

    The problem doesn't seem to be weather dependent and now is getting worse a bit each day. I'm no longer having a few pops upon acceleration but rather long sets of skips or stutters that last a little bit after the car shifts into second. I'm concerned it may be the timing, but I know nothing about how to adjust that beyond turning the distributor one way or the other. I'm beginning to suspect that I have little choice but to take it in for work.
     
  7. Bryant

    Bryant forgot more than learned

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    you need to learn how to set and adjust your timing to be able to tune your engine.
    first you need to purchase a timing light.
    now you need to find and mark your timing marks on the balancer. the marks are usually pretty hard to see. i will take some sort of paint, white out, touch up paint, wifes nail polish, or a sliver sharpie and mark the timing marks on the balancer.
    then i will also put a mark on the pointer to make it easy to see.
    hook up the timing light to the #1 cylinder spark plug.
    disconnect the vacuum advance hose on the distributor an plug the hose going to the carb.
    now you can start the motor and see what the timing is.
     
  8. Ian240B

    Ian240B Member

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    This is what I was missing. I thought the marks were painted on already, thus they were missing, but they are etched in and not painted hence why I can't find them. Thanks for the tip, this is exactly what I needed to know.
     
  9. John Holden

    John Holden Member

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    Put a volt meter on the car and test with the engine off and then test again with the engine running. Your "new" alternator may not be working. Low voltage will cause all sorts of problems like the ones you are describing.
     
  10. Ian240B

    Ian240B Member

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    Ya know, the ALT light has been flickering a bit at lower RPMs pretty much since this issue arose again.
     

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