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  1. #1
    Carb and Points!
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    Runs worse as it learns....

    Hello,

    I've got a complicated system with a few problems I'm trying to work out. By complicated I mean I'm running a GM based TBI system from Affordable Fuel Injection (they have been almost zero help) on a 1984 Dodge W350 Crew cab with a 360 that has been stroked out to a 410 stroker motor. It can make a lot os HP and torque if it runs right. I have a 454 TB and for sensors I have an IAC, MAP, Temp, TPS. No knock sensor. For ignition I'm using a stock MOPAR distributor (magnetic) with the advance welded and a GM ICU. I've checked it thoroughly for vacuum leaks and I get no trouble codes.

    I'm finding my GM TBI system gets worse over a period of a few days... If I pull power to the ECM then reinstall the fuse it runs pretty good for a few days and the slowly gets worse and worse. I get what feels like a lean miss and eventually it backfires on acceleration. if I reset the ECM again it gets better for a few days and then slowly come back to the poor running.

    I also have problem with spark advance. If I set my base timing to zero degrees (unplugging the wire) I get lots of pinging right off the bat without even giving wide open throttle...really bad.So I've been running it with the base timing set to about 8 degrees retarded and although the pinging issue is nearly gone, I've also lost most of my power and the mileage sucks. I've tried swapping the ICU with no change. I also pulled the distributor and made sure everything was still welded together (the advance is welded) and nothing was sloppy or loose.

    I do not know what my injectors are and the folks at Affordable have no idea what they sold me either (jerks), BUT I took them to a place in Gladstone and had the guy flow test them. He said they are both even and have a nice pattern, BUT they are huge injectors...they tested at 180 at every pressure he put through them. I am running 26 psi fuel pressure (that's the way it was setup when it came).

    I hate simply swapping parts....so I'm trying to get some advice on what my problems might be. I believe I have a couple of them at least.

    Any thoughts??

  2. #2
    billygraves
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    Last edited by billygraves; 06-30-2019 at 06:25 PM.

  3. #3
    Fuel Injected!
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    I didn't see the ECM service part number in the list of info billygraves asked for so provide that too.

  4. #4
    Carb and Points!
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    The engine was built at the same time the TBI system was added.
    Forged pistons, 10:1 compression (I always run premium), Cam is a custom grind with Exh lift 444, Centerline 114, Duration 214, Intake Lift 443, Centerline 106, Duration 214, Cam timing is 105 degree intake, Rockers are OEM, Stock Cast iron intake with an adapter plate to attach the TBI unit.
    ICM is a stock GM (currently an Autozone part), mounted to a heat sink with heat transfer paste (aluminum plate) mounted to the inner fender well away from heat and grounded well. Distance from ICM to coil by wire is probably three feet at max. The pickup wires from the distributor to the ICM have no shielding.
    Os sensor is a 3-wire, heated unit, I have no idea what the brand is but told (by AFI) that if it needs to be replaced that a unit off of a 1995 Chevy K2500 w/ 350 will fit. The O2 sensor is mounted in a bung on the passenger side header collector.
    Wiring harness custom built for the app by Affordable Fuel injection which supplied the whole kit and was supposed to custom burn the chip for the application.
    I'm not sure about the ECM ground questions...I'm an electrician, I try to make sure everything is grounded to clean bare metal. The block and the body and frame are all bonded together well.
    I have both ALDL and TunerPro software. I can record data easily with the ALDL software, but I haven't figured out the TunerPro software quite yet.
    The injectors don't appear to leak.
    The system did not come with a knock sensor, AFI knows it does not have a knock sensor and I assume they programmed the chip accordingly.
    No idea if the EECM is a reman. I only know that it did not look new and I've swapped the EPROM several times with new burns from AFI.

    I think that answers most of your questions...let me know if I missed anything.

  5. #5
    Carb and Points!
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    Also, the truck has a manual transmission.

  6. #6
    Carb and Points!
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    The ECM is a 1227747...is that what you mean?

  7. #7
    LT1 specialist steveo's Avatar
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    a few days is a long time; but if you unplug the o2 sensor, does it continue to run poorly for a few days?

    who tuned this thing?

    why are you still running a botched timing map?

    sounds like maybe just a bad tune...

  8. #8
    billygraves
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    Last edited by billygraves; 06-30-2019 at 06:25 PM.

  9. #9
    LT1 specialist steveo's Avatar
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    definitely good info, especially about the plug wires and shielding the pickup wires. i've gone through the exact same shit another car before, and now you reminded me to check mine out.

    but yeah it does sound like it needs a retune

    AFTER you resolve all other possible issues.

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