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  1. S

    97 K3500 fresh engine runs great in open loop and horrible inj closed loop.

    Thanks for the help. Ok now I am getting somewhere. What is a 411 swap? I will take a look at the PCM Hammer software and needed hardware. It looks like I will have to educate myself to make any headway. Two different folks who were recommended by others, to make changes to my black box said...
  2. S

    97 K3500 fresh engine runs great in open loop and horrible inj closed loop.

    I was told by a number of tuners that you cannot datalog the computer in 7.4 powered trucks in 96 and 97. Because the truck is so old I cannot find any tuner that knows anything about them.
  3. S

    97 K3500 fresh engine runs great in open loop and horrible inj closed loop.

    The wires are exactly like the factory set-up and use the stock clamps Because I like to keep things tidy.
  4. S

    97 K3500 fresh engine runs great in open loop and horrible inj closed loop.

    The PCM in 1996 to 97 7.4 trucks will not allow for data to to recorded to a file. It is called a black box PCM. I can drive the truck and watch what is happening but it will not save the data.
  5. S

    97 K3500 fresh engine runs great in open loop and horrible inj closed loop.

    Both are new and according to my scanner they are working fine. It does not stay in open loop when O2's are unplugged. Every sensor on this truck test fine and look good while driving. It is a random misfire.
  6. S

    keeping my K3500 7.4 truck in open loop

    Good question. Fresh engine all new computer, all sensors . no codes. Runs perfect in open loop the minute it goes into closed loop it misfires and runs like crap. Scan tools show everything is fine. O2 working as should long a short term trim is good fuel pressure hangs in a between 55 and 60...
  7. S

    97 K3500 fresh engine runs great in open loop and horrible inj closed loop.

    Plug routing is nice a tidy and all new. no crossing wires. Everything that folks have offered so far has been done if it were possible. There is nothing old left to replace. In a number of cases I have replaced things twice. I did find one suspect knock sensor but it did not fix...
  8. S

    97 K3500 fresh engine runs great in open loop and horrible inj closed loop.

    Turns out is was a random misfire.
  9. S

    97 K3500 fresh engine runs great in open loop and horrible inj closed loop.

    I wish, I have already tried to have the data recorded to send out for a tuner to have a look. When I told him the year he said, 1996 to 1998 will not allow data to be recorded. I cannot record real time data from this computer. Now I just want to make it stay in open loop and let rip. It runs...
  10. S

    keeping my K3500 7.4 truck in open loop

    Is there a way to program my 97 K3500 to stay in open loop?
  11. S

    97 K3500 fresh engine runs great in open loop and horrible inj closed loop.

    Ok it has been a while. I am still having this problem. In open loop this truck hauls the mail. In closed loop it misfires under load. Scan tools shows everything is right where it should be. Zero codes. Fuel pressure is between 55 and 60 psi all the time. There are no codes. I have replaced...
  12. S

    97 K3500 fresh engine runs great in open loop and horrible inj closed loop.

    The engine is fresh, all the sensors are new and on a scan tool all are working. At last check all the misfires were on #5, changed spark plugs and wires, new cap new rotor, new coil, new module, tested three know working PCMs one with a tune for header, no cat and 2.5 " Xpipe exhaust which is...
  13. S

    97 K3500 fresh engine runs great in open loop and horrible inj closed loop.

    1997 7.4 K3500,fresh stock build no cats JBA stainless headers, no cats 2.5” dual exhaust with X pip[e back to rear axle then trough a flow master two in one out muffler. Pulls like a train in open loop..about 1.5 miles then switches to closed loop where it falls on its face. Surges and...
  14. S

    7.4 vortec stock idles at 24 degrees advance but retards to 10 under any load.

    It this normal to see 24 degree at idle and instant drop to 10 degrees under even the lightest load? Knock sensor is not tossing codes.

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