Rebuilt CCC Qjet Tuning

Discussion in 'Engine Topic' started by MP81, Oct 8, 2019.

  1. RickM

    RickM Veteran Member

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    Just do it in the garage, the car should go into closed loop after 5 minutes or so, unless it is really cold outside.

    My 81 does the same as you were describing, when the car goes into closed loop the rpm's jump up for a second or two.

    Kind of sounds like your car is not going into closed loop, maybe you need to double check the o2 sensor wires.

    RickM
     
  2. MP81

    MP81 Veteran Member

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    Okay, so just warming it up is fine then.

    Should be in the high 50s on Thursday, so I'll plan to check then and see what I can find.

    Does the green diagnostic wire go back to the ECM? I want to make sure that nobody in their infinite wisdom (prior to me having the car) snipped that wire - this car has had like four alarms. I swear my uncle must have constantly gotten it upgraded and they just left half the poo from the old one in there, so there is a mess of wiring everywhere.
     
  3. RickM

    RickM Veteran Member

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    Yes green wire is circuit #411 goes to pin 18 of the ECM which is the mixture control solenoid output signal.

    The green wire is connected to the mixture control solenoid, that is what the dwell meter is looking at the duty cycle of the mixture control solenoid.

    upload_2020-3-31_12-26-6.png

    Sorry for the lousy picture but here is the connector from the schematics, pretty simple.
     
  4. MP81

    MP81 Veteran Member

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    So I should technically have continuity between the "test end" of the green wire and the green wire going into the MCS connector? Runs from MCS to the ECM and then to the test end?
     
  5. RickM

    RickM Veteran Member

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    Yes, you should be able to ohm that and see continuity
     
  6. MP81

    MP81 Veteran Member

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    Cool, that'll be an easy test to make sure I don't have a break in the wire, causing me to chase my tail.
     
  7. MP81

    MP81 Veteran Member

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    All right, so I let it run for about 10 minutes today - revs jumped to like 2000 a few minutes in all of a sudden, but I went out and checked, and it didn't seem like the high idle cam dropped like it is supposed to, so I pushed it down and the car dropped back down to the proper idle. The revs jumping must've been something electronic since it was so sudden and out of nowhere, expecting the high-idle cam to have dropped. That stupid thing has never worked smoothly, though it seemed to be better when I rebuilt the carb. It did sit all winter, so it could just be "frozen" a bit.

    Either way, dwell remained at 3 degrees on the six-cylinder cycle (I did verify yesterday that I have continuity between the MCS wire and the diagnostic connector, so that isn't the issue). I covered the choke horn with my hand, and the reading did not change - though the car revved up after a few seconds of choking the carb to keep itself running, and after I moved my hand away, it dropped back down after a few seconds. That tells me something is working...but I'm not sure what.

    Stupid question...but the fact the entire AIR/smog system is removed wouldn't be causing this, would it?
     
  8. frank5s

    frank5s Veteran Member

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    AIR / smog adds air to the exhaust which the O2 sensor read. Might have something to do with it. Probably reads real rich, try creating a huge vacuum leak by taking off brake booster hose and see if dwell changes
     
  9. Rustbucket350

    Rustbucket350 Veteran Member

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    The whole problem here is the computer quadrajet. It is not a good system today and it never was. I admire anyone being determined to getting it to work correctly but its never going to happen. Dude ill give you two non computer q jets that are complete but dirty just to take the headache off your hands. Put a real carb on, tune the ignition. No more problem.
     
  10. bourbon_scotch

    bourbon_scotch Veteran Member Lifetime Gold Member

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    get rid of it
    will those cars actually shut you down if you dont use it?
     
  11. Rustbucket350

    Rustbucket350 Veteran Member

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    They more than likely weren't designed that way but I'm willing to bet the fuel whether its todays fuel or regular straight gas will gum up the idle control solenoid in the carb.

    Even if it doesn't, its still tuning around GMs piss poor first attempt at a more emissions satisfactory vehicle. I bet you could put a single feed holley 4160 on that and still pass emissions if you had to if it was tuned properly. Then pick up some lost power.
     

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