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Thread: No idea what to try next...

  1. #11

    Default No idea what to try next...

    GTR,

    What does the MAP show (on the Dash) at key-on, engine off?

    Please verify that BOTH main power leads (heavy RED and heavy BLACK) of the MSD box are connected at the battery for best output of the ignition.



    Also, with the plugs fouling out, the O2 sensor may be fouling as well, giving a false lean reading causing it to put more fuel in.

  2. #12

    Default No idea what to try next...

    Hi MSD,



    My KOEO MAP reading is usually around 27" to 29".



    Both red and black wires are connected directly to my new Optima red top battery terminals.



    I am concerned that the O2 sensor may be fouled too but it does appear normal on the display and it hasn't registered an error code in the diagnostics. Is there any way to clean the O2 sensor or is it a replace as required item? Can I somehow test the O2 sensor to determine if it is working properly?

  3. #13

    Default No idea what to try next...

    There is no recommended way to clean an O2 sensor, it is best to replace it.

    We have it available as PN 2930.

    Unfortunately it is not possible to test an O2 sensor out in the field.


  4. #14

    Default No idea what to try next...

    Can I assume that the O2 sensor is OK if the diagnostics don't detect anything wrong with it and it's still showing me the AFR readings? I'm asking this for two reasons, 1. I would have to wait quite a while for a replacement, there aren't any local outlets for these and 2. I don't want to put a new sensor in and have it go south on me right away too.

  5. #15

    Default No idea what to try next...

    Just thought of another thing that I mentioned previously and don't know the answer to. Why would my IAC indicate a value (I've seen anywhere between 7 and 42) while I'm driving at a steady speed?

  6. #16

    Default No idea what to try next...

    GTR750EVO wrote:
    Can I assume that the O2 sensor is OK if the diagnostics don't detect anything wrong with it and it's still showing me the AFR readings? I'm asking this for two reasons, 1. I would have to wait quite a while for a replacement, there aren't any local outlets for these and 2. I don't want to put a new sensor in and have it go south on me right away too.



    Not necessarily, a fouled (or partially fouled) O2 sensor may not set off an error if the values are still within "normal operating range".

  7. #17

    Default No idea what to try next...

    GTR750EVO wrote:
    Just thought of another thing that I mentioned previously and don't know the answer to. Why would my IAC indicate a value (I've seen anywhere between 7 and 42) while I'm driving at a steady speed?




    The IAC programmed to follow the throttle (TPS). This helps to prevent stalling on sudden decal. This sort of works like an anti-stall dashpot used on some older carbureted applications.

  8. #18

    Default No idea what to try next...

    Hi,



    I've been thinking about this one a lot as my car is doing something similar altough it is more like hesitation and coughing at 1200 rpm on light throttle setting which can be sorted by pushing harder on the loud pedal. I've concluded that it is probably my connection between the headers and exhaust that is leaking and giving false AFR readings so have some paste and a stronger clamp in the mail.



    I have also been trying to figure out the rotor phasing adjustment too. The instructions state that the rotor should be retarded by 15 degrees (although the guy on the youtube video states that it should be advanced by 15degrees but actually he retards it on the rotor).



    So this got me thinking, the 15degree static advance on the timing is presumably just a arbitrary mid point figure between the two timing extremes that most of us are likely to use. When the ecu is firing the ignition ahead of 15 degrees of advance then it must be actually predicting the timing of the particular cylinder based on the timing of the three previous cylinders. It will have to use the three previous measurements in order that it can come somewhere close to an accurate prediction in an engine that is accelerating or decelerating. Obviously this is only a problem for timings ahead of the 15 degree static position.



    If I recall correctly obtaining an accurate prediciton for timing of an engine during the acceleration and deceleration phase was the reason the manufacturers moved to reluctor rings to provide many more pulses per engine revolution.



    Anyway back to the point. Would I be right in thinking that the only real reason for retarding off the rotor phasing is to cover the case where nitrous is being used and the timing may have been backed off to 20 degrees retarded and that for the majority whose timing never dips below 6 degrees advanced then changing the rotor timing isn't actually necessary?



    Also, when I've resealed my headers I will come back to the thread to let you know if it made any difference.








  9. #19

    Default No idea what to try next...

    I think you might be reading a little too much into the retarded rotor set up.



    If I'm wrong about this, hopefully someone will correct me.



    I've come to the conclusion that the retarded rotor just positions the rotor in a location that will allow the Atomic to vary the timing of the actual spark when it's required and the spark will "walk" across the tip of the rotor from the back edge of the rotor to the front edge while it's advancing the spark. This is hard to explain in text and I'm hoping it's making sense. If this is completely incorrect, someone please let me know and explain the way it actually does work. Thanks.

  10. #20

    Default No idea what to try next...

    you're probably right but with the rotor too far retarded and the ecu advancing the spark (remember that with 35degrees of total adavance the coil is firing 20degrees before the magnetic pickup aligns in the distributor). This could lead to the spark jumping to the distributor terminal linked to the previous cylinder and actually firing a cylinder that 55degrees after TDC i.e. in effect making the engine run 55degrees retarded. I think you mentioned that you were using the 84211 (or I may have seen this somewhere else) but this is a small dizzy cap and the terminals are quite close together...



    As you say, it's hard to put this down in text in a way that makes sense but hopefully the MSD guys will provide some more information...

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