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    Hot idle/Air-Fuel Mix issue??

    Hi everyone. I need some wisdom. I have solved the fuel line issue but now my carb needs some adjusting... I think. Here's the symptoms.

    Cold - Everything is fine, the car runs like a champ.

    Hot - The idle surges and dies out in a rhythmic fashion... like it's flooding out over and over again. It's also running quite rich. If you leave it too long it eventually stalls... if you're driving and slow down it stalls (i.e. at any stop or when cruising around a residential neighbourhood and coming to a turn or something).



    I'm wondering if this an air fuel mixture and/or hot idle setting issue... and if so how do I adjust these properly without having to attach a tach?

    Just a reminder, my car is an 85 Crown Vic with a 302 and a 2bbl Carb. [That's how some of them came in Canada ]
    ************************************************** ******************************
    1997 Crown Vic - Mostly rust free, moderate mileage. On the road... but far from perfect. **SOLD**
    1985 Crown Vic in 2-Tone Blue **SOLD**
    http://automophiliac.blogspot.ca/

    #2
    I did some research and poking around online. Found that the air fuel mixture for idle can be adjusted by two screws located at the front of the carb under the accelerator pump.

    Check out this great writeup on Motorcraft 2bbl carburetors by Dave Resche:

    http://grantorinosport.org/bubbaf250/carb/carb02.html

    I did run into a stumbling block though. Where my adjustment screws are, there are these black rubbery/plastic marshmallow shaped things. I thought maybe they are a protective covering for the screws... but they don't come off easy and I didn't want to mess anything up by hulk smashing them off. Does anyone else have a carb panther with this sort of set up (marshmallows and all?).

    Cheers!
    Last edited by SeanP; 07-04-2015, 09:37 PM.
    ************************************************** ******************************
    1997 Crown Vic - Mostly rust free, moderate mileage. On the road... but far from perfect. **SOLD**
    1985 Crown Vic in 2-Tone Blue **SOLD**
    http://automophiliac.blogspot.ca/

    Comment


      #3
      Of course this video may answer my questions too...

      https://www.youtube.com/watch?v=v0P-m4p60IU

      Choke adjust... he seems to have a similar set up to me. I'll try this in the morning.
      ************************************************** ******************************
      1997 Crown Vic - Mostly rust free, moderate mileage. On the road... but far from perfect. **SOLD**
      1985 Crown Vic in 2-Tone Blue **SOLD**
      http://automophiliac.blogspot.ca/

      Comment


        #4
        Check the choke adjustment. If its not opening when hot, it will run rich. The thermal heater is the hockey puck looking device on the side. Make sure the wires are still plugged in to it. This also relies on the alternator working to operate, so if the alternator isn't alternating for some reason, that'll do it.
        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

        Comment


          #5
          Originally posted by gadget73 View Post
          Check the choke adjustment. If its not opening when hot, it will run rich. The thermal heater is the hockey puck looking device on the side. Make sure the wires are still plugged in to it. This also relies on the alternator working to operate, so if the alternator isn't alternating for some reason, that'll do it.
          Cool. That makes sense based on what i've been reading... it needs to be straight up and down when hot right? I think mine is a little closed-ish while running... may explain things.

          I'll check everything in terms of wires and such.

          My alternator woes are all sorted so no problem there!

          Thanks again!
          ************************************************** ******************************
          1997 Crown Vic - Mostly rust free, moderate mileage. On the road... but far from perfect. **SOLD**
          1985 Crown Vic in 2-Tone Blue **SOLD**
          http://automophiliac.blogspot.ca/

          Comment


            #6
            There is something about setting the choke gap when cold using a drill bit of some size. I don't recall the particulars but you should be able to find the setup for a 2100 or 2150 easy enough. If it doesn't open from that point, the heater may be dead. There is a vacuum choke pulloff, but it works in conjuction with the heater setup. If the heater isn't doing it's job, the choke won't fully open.


            make sure the pulloff holds vacuum too. if its leaky, it won't work right. It should be the thing on the back side of the carb, passenger side, with the short vacuum line connected to the body of the carb.
            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

            Comment


              #7
              Originally posted by gadget73 View Post
              There is something about setting the choke gap when cold using a drill bit of some size. I don't recall the particulars but you should be able to find the setup for a 2100 or 2150 easy enough. If it doesn't open from that point, the heater may be dead. There is a vacuum choke pulloff, but it works in conjuction with the heater setup. If the heater isn't doing it's job, the choke won't fully open.


              make sure the pulloff holds vacuum too. if its leaky, it won't work right. It should be the thing on the back side of the carb, passenger side, with the short vacuum line connected to the body of the carb.
              I set the choke so that it is wide open when hot. Still have stalling/hesitation issues while driving though... I'm wondering if the mix was lean and someone set the choke back to compensate for it?? I think if I could get more fuel with the open choke I'll be in business. Maybe... to be honest the carb probably just needs a rebuild.
              ************************************************** ******************************
              1997 Crown Vic - Mostly rust free, moderate mileage. On the road... but far from perfect. **SOLD**
              1985 Crown Vic in 2-Tone Blue **SOLD**
              http://automophiliac.blogspot.ca/

              Comment


                #8
                Ok, so I've done some fiddling. I set the choke too wide open so it wouldn't close for cold starts. The choke plate is now set perfectly (about 3/16 drill bit gap cold, wide open hot). Still a little love needed to get her started, but this isn't new... once she gets going and the high idle fully kicks in she runs strong.

                I monitored the choke plate operation, and like I said above, working great.

                Hot idle is a still surging a little (like someone is slightly revving the engine over and over again). When I take the air cleaner off, it is less noticeable. When I plug the vacuum line going to the air cleaner (the red one at the back of the engine) the idle bogs down a bit and the surging is more noticeable.

                Also, when the car is put into reverse, it works great. When I put the car into drive, it gets bogged down and will sputter or stall (usually the latter). This includes when coming to a stop or a big slow down (turning tight corners). It doesn't do this as much when the fast idle is still running, but does every time pretty well when hot.

                There is also hesitation on throttle input, but once it gets going it's fairly smooth, though there is some hesitation when the amount of throttle being applied changes. Kickdown is strong once the initial hesitation is through. Runs like a champ.

                So does this sound like vacuum leak or a carb rebuild needed... or both? I will be doing a vacuum leak check sometime this week and I'm thinking of doing an overhaul on the carb and then seeing if that corrects some of the issues I'm having. After that's done, I'm pretty much out of ideas.

                I just want my baby to be happy!!!
                ************************************************** ******************************
                1997 Crown Vic - Mostly rust free, moderate mileage. On the road... but far from perfect. **SOLD**
                1985 Crown Vic in 2-Tone Blue **SOLD**
                http://automophiliac.blogspot.ca/

                Comment


                  #9
                  Could be either, but check for cracked vacuum hoses first. They tend to cause all sorts of nonsense. Not sure what exactly you guys got, but here our carb cars in the 80s had a ton of thermal vacuum switches and other nonsense that went bad and leaked. If you've got all that junk, you'll really need to test all of it for proper function. This might require the emissions manual to show proper function of those parts.

                  Related question, but is the timing set properly, and are the ignition parts in good shape? Not sure if you guys had the 3 plug Duraspark box, but if you do there is a specific way you have to set the timing on those. Destructions will be under the hood, but I believe its the 2 wire plug that you unhook and jumper together on the box side to set the timing. The vacuum and mechanical advance in the distributor also needs to work. Vac is easy, just apply vacuum and make sure the timing moves. Mechanical is similar, but you rev the engine and make sure the timing moves. If the weights are stuck or worn, the advance plate won't move properly and it'll tend to do stupid things.
                  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

                  Comment


                    #10
                    I realize I'm a bit late replying, but here is my advice (I have a 2150 carb) if you don't know when it was rebuilt last, do yourself a favor and get a rebuild kit and go to town. It isn't that hard to do although it may seem intimidating at first. Once you have replaced everything needed, use the website you have been looking at, or better yet the instructions that should come with the rebuild and set all adjustments back to where they should be. It sounds like you are halfway there knowing how to set the choke.

                    You HAVE to access the idle screws to do his, not sure why they are covered to be honest, but they are adjustable. Once you set everything back to factory specs it should run pretty well, certainly better than it is now if you did everything correctly. I had to lean mine out to pass emissions here,but it ran fine a little rich.

                    I hope this helps.
                    -Phil

                    sigpic

                    +1982 Ford LTD-S Police Car. Built 351w, Trickflow 11R 190 Heads, Holley Sniper EFI, RPM Intake+ Hyperspark dizzy, WR-AOD, Full exhaust headers to tails. 3.27 Trac-Lok Rear. Aluminum Police Driveshaft. Speedway Springs+Bilstein Shocks, Intermediate Brakes, HPP Steering Box.

                    +2003 Acura CL Type S 6-speed

                    Comment


                      #11
                      Thanks for the tips guys... as always, the membership here never fails to astound with how knowledgeable and helpful they are!

                      My dad's coming over tomorrow and we're going to do a check of all the vac lines, check the ignition timing and figure out the adjustment screw issue.

                      I think at this point, I'm fully resolved to do a rebuild on the carb. I don't think it's ever been done and it's been sitting for 10 years... should probably be done just 'cause. I've sourced some kits and they are quite inexpensive. I'm not too intimidated by the prospect, but I'm certainly carrying a healthy amount of respect for what I'm about to do!

                      I'll post an update after we see what happens tomorrow.
                      ************************************************** ******************************
                      1997 Crown Vic - Mostly rust free, moderate mileage. On the road... but far from perfect. **SOLD**
                      1985 Crown Vic in 2-Tone Blue **SOLD**
                      http://automophiliac.blogspot.ca/

                      Comment


                        #12
                        well, if its been sitting for 10 years that would be enough to warrant a rebuild. If the fuel dried in the bowl, it'll have at least some amount of crust in there, and I wouldn't expect the accelerator pump or the power valve to be in optimal shape either.
                        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

                        Comment


                          #13
                          Originally posted by gadget73 View Post
                          well, if its been sitting for 10 years that would be enough to warrant a rebuild. If the fuel dried in the bowl, it'll have at least some amount of crust in there, and I wouldn't expect the accelerator pump or the power valve to be in optimal shape either.
                          I've got a line on a rebuild kit, going to get a new float too. Also, I don't think the throttle modulator is working right. We tried adjusting the idle and it just wasn't working that well. Now it's worse than ever in terms of idle roughness, but it doesn't seem to stall as much when in gear. Curiously enough. I'm thinking the vacuum diaphragm may be toast or close to it. One thing after another
                          ************************************************** ******************************
                          1997 Crown Vic - Mostly rust free, moderate mileage. On the road... but far from perfect. **SOLD**
                          1985 Crown Vic in 2-Tone Blue **SOLD**
                          http://automophiliac.blogspot.ca/

                          Comment


                            #14
                            Sounds like a vacuum leak to me, but a carb rebuild definitely wouldn't hurt. My fuelie car had a similar surge and would occasionally stall when stopping. Once I fixed the vacuum leak it all went away.

                            Comment


                              #15
                              Originally posted by knucklehead0202 View Post
                              Sounds like a vacuum leak to me, but a carb rebuild definitely wouldn't hurt. My fuelie car had a similar surge and would occasionally stall when stopping. Once I fixed the vacuum leak it all went away.
                              Yeah, there is probably a vacuum leak there somewhere too. Problem is finding it and then fixing it I have tried a few ways and I feel totally stumped because I can't seem to find one. How did you manage to find yours?
                              ************************************************** ******************************
                              1997 Crown Vic - Mostly rust free, moderate mileage. On the road... but far from perfect. **SOLD**
                              1985 Crown Vic in 2-Tone Blue **SOLD**
                              http://automophiliac.blogspot.ca/

                              Comment

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