Rebuilt CCC Qjet Tuning

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

  1. RickM

    RickM Veteran Member

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    Well by the time the thermostat opens it should be warm enough. But what you really want is for the 02 sensor to start producing a signal. That happens when the exhaust gas gets hot enough causing the elements in the sensor to get hot enough and start producing a voltage.
     
  2. MP81

    MP81 Veteran Member

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    Yeah, that's usually what a watch for. Myself being an intellectual installed the DD gauge coolant temp sensor in the thermostat housing - so it only starts moving once that opens. A dumb place to put it - but sure is convenient here!

    Prior to that, the dwell shouldn't be constant, right? I thought I read that it should be moving around before it goes into closed loop? Or maybe I am remembering incorrectly.
     
  3. RickM

    RickM Veteran Member

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    Meter will not move until it goes into closed loop. Is your O2 sensor old? If so you should replace it. Go with a GM unit they are more expensive but some of the other sensors are "lazy", they will work but not as well as a genuine GM.
     
  4. MP81

    MP81 Veteran Member

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    It's definitely old. I have a brand new Bosch 12028 sensor that I bought when I installed the headers, but since I had to lengthen the harness on the O2, I ended up doing it on the old one, versus cutting up the new sensor. Based on the images - the Bosch 12028 is the OE sensor - the other sensors all look different, whereas the Bosch matches the AC Delco GM OE one (which is likely why I bought it). I really wish someone made the vehicle-side end for the two-wire O2, so I could make an extension harness, rather than modifying the actual part, which I never like doing.

    Would the sensor throw a code if it had issues, or not?
     
  5. RickM

    RickM Veteran Member

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    I have the Bosch sensor also and it seems to be fine. If the O2 sensor is bad you will eventually get a code related to it either a lean condition has been sensed or a rich condition has been sensed. There is also a code if no O2 readings are present. If you chopped up the original O2 harness that may be a problem also. Service manual says to never probe the wires with a scope or multimeter. May have something to do with the resistance of the wire. I know O2 sensors provide a very low voltage signal. Changing the resistance of the wire may not be a good thing. I am just guessing on this so take it with a grain of salt. Also is your coolant temp sensor old? Without that working you will never go into closed loop. The ECM should throw a code if it does not get a reading from it.
     
  6. MP81

    MP81 Veteran Member

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    That's the thing though - it ran the same as before after I did the headers (which includes extending the O2 - I used 16 gauge wire, so resistance shouldn't be an issue), and I still had the coolant reading on my original cluster.

    It was practically an over-winter issue (on its own) where the vehicle went from funky-ish at idle and wine at WOT to perfect at idle, but funky-ish at part throttle and useless at WOT. Now that the carb is rebuilt, it seems like we're back to the former. I bet if I go out and drive it, it might actually be just like it was before it went all crazy.

    Regarding codes, the only time that comes on is when the idle starts getting really low...so I turn the car off while the CEL is still illuminated, and go to read codes and get...just 12s on repeat. No actual code that it seemed to think it had.
     
  7. MP81

    MP81 Veteran Member

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    All right - just went out and checked solenoid travel - 13/128" - after a "tweak" to the rich stop (which has the plug removed, but I am not entirely sure is adjustable - almost impossible to turn, but I'm guessing I must have just barely done so), that travel is 3/32" - right in between the 2/32" and 4/32" threshold (the service manual says 3/32" when adjusting the solenoid travel, so I'd say that is about perfect). But 13/128" is basically "3.25"/32", so it was good to go prior, as well. Now it's just better.
     
  8. RickM

    RickM Veteran Member

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    I am not talking about your temp sender I am talking about the coolant temp sender to the ECM. It should be right next to the thermostat, screwed into the intake manifold.
     
  9. MP81

    MP81 Veteran Member

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    Have a picture of that one? I can't say I recall ever seeing something like that - only the one in the side of the head.
     
  10. RickM

    RickM Veteran Member

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    Here you go

    [​IMG]
     

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