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Thread: High idle speed

  1. #1
    Fuel Injected! CDeeZ's Avatar
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    High idle speed

    Whenever I'm driving around and I pull out of gear or disengage the clutch, it seems like it takes forever for the idle to settle down from around 2Kish RPM down to around 1Kish.

    I tried to fix this with some stuff I read about from RBob's notes on IAC logic "To reduce flair-up on engine start:

    Lower the park position @ 0x5C2.
    Lower the park to run delay @ 0x5C3.
    Lower the kickdown time delay @ 0x5D7.
    Lower the coolant vs. position values @ 0x5F5.


    To quicken the return to idle after throttle blip:

    Set delay @ 0x5E7 to 0.
    Increase filter coefficient at 0x5E4.
    Reduce throttle follower percentage @ 0x5F0 & 0x5F1."



    Not sure if it helped really though....

    Here is the original thread http://www.thirdgen.org/techboard/di...-follower.html from the prom tuning guidebook on TGO



    What do I need to do to fix this?

    '747 $42 L05......

  2. #2
    EFI GearHead ! EagleMark's Avatar
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    Is the motor stock?

    Could be a mechanical issue as well.

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
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  3. #3
    Fuel Injected! CDeeZ's Avatar
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    Not stock at all. Nothing wild either.

    mildly cammed, ported and polished 193 heads, high volume oil pump, ported-enlarged-and-relieved oil return holes in lifter valley, Ultimate TBI, TB spacer, pod spacer, midlength headers, dual 3" exhaust with H pipe and turbo style mufflers. I think that's about all.

    Not sure what kind of mechanical issue it could be, everything seems pretty solid with it.

    I think it's my tune being so rough maybe?.. my tune is still pretty close to stock, which likely needs much more tweaking from the changes I made to the engine over stock.
    Last edited by CDeeZ; 06-27-2012 at 05:18 PM.

  4. #4
    EFI GearHead ! EagleMark's Avatar
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    Not sure what kind of mechanical issue it could be, everything seems pretty solid with it.
    Vacuum leak?

    Got a log that starts with engine totallyu warmed up and all things in XDF turned off for data logging?

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
    -= =-

  5. #5
    Fuel Injected! CDeeZ's Avatar
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    Here is a log I did today.

    I don't see any vacuum leaks
    Attached Files Attached Files

  6. #6
    Fuel Injected! jameslleary's Avatar
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    Dual 3" exhaust!!!?
    Have you checked your brake booster for Vacuum leaks?

  7. #7
    Fuel Injected! CDeeZ's Avatar
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    Yeah, 2.5" would have been plenty I'm sure, but I figured if I do any kind of upgrades down the line (forced induction and/or bigger displacement engine) then the 3" pipes would be nice to have.

  8. #8
    Fuel Injected! jameslleary's Avatar
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    Sorry we posted at the samentime...Brake booster. Your low end must suffer pretty badly.

  9. #9
    Fuel Injected! CDeeZ's Avatar
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    Yeah I'm pretty sure the brake booster is ok but how would you check it?

    Actually the low end is excellent, like just about any TBI.. Amazing low speed torque, crisp throttle response and good fuel mileage, (for a pushrod V8 based on 1955 SBC architecture.)

    I think having the H pipe really helps out with the low end and just all around power in general, the 3" pipes are about as big as I could have gone probably, any bigger would have been TOO big.

    But no, the low end is spectacular, with no shortage of stump pulling torque. I can leave pretty hard in 1st gear and still chirp the tires all the way through 5th gear. Never been able to chirp it in 6th but by the time I hit 6th gear I'm already going 70+ MPH

  10. #10
    Fuel Injected! jameslleary's Avatar
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    If you have access to a smoke machine, fill it with smoke through the vac line hole, and see if any escapes.
    Last edited by jameslleary; 06-27-2012 at 07:34 PM.

  11. #11
    Fuel Injected! JeepsAndGuns's Avatar
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    I remember back in my early days when I was still running the 7747. I had a simmilar issue with the idle hanging like that, most noticeable at warm startup. I tried a few difffrent things before I got curious and changed a parameter called "IAC reset Vs baro" I was at my witts end. I started out reduceing them a bit, then I changed all to zero and it cured my problem. Not sure if it will have the same results for you, but its worth a try. Take and write down what values are in that table, then change them all to 0. That way, if it doesnt work, you can change them back.
    Table is at 0x606. 42.xdf calls it "IAC reset Vs barometric" Marks 42-1227747-V4.3.xdf calls it "IAC baro reset"
    79 Jeep Cherokee, AMC 401, T-18 manual trans, hydroboost, 16197427 MPFI system---the toy

    93 Jeep YJ Wrangler, 4.0L, 5 speed, 8.8 rear, homebrew hub conversion and big brakes, hydroboost, 2.5in OME lift, 31x10.50's---the daily driver

    99 Jeep WJ Grand Cherokee limited, 4.0L, auto, 2wd, leather and power everything, 99% stock---the long distance highway ride.

  12. #12
    Fuel Injected! CDeeZ's Avatar
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    I'm thinking seriously about a 7427 swap. Something like EBL would be nice, but since I already have the chip burning equipment, swapping in a 7427 seems to be the best/easiest/cheapest way to upgrade. I would think the more advanced code, faster speed, and higher res. tables would be reason enough to swap a 7747 for a 7427.

    In the meantime, I tried zeroing out the IAC vs baro table you spoke of, and it did indeed seem to make an improvement! Thank you

  13. #13
    Fuel Injected! JeepsAndGuns's Avatar
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    If you do the 7427 swap, you wont be disappointed! If you feel comfortable swapping the pins, and are not too overwhelmed by the verry long list of parameters, go for it!
    If you havent already, grab the $0D.XDF from the 7427 thread, and mabey a bin too, load them up in tuner pro and just look around. Its a lot to take in at first. When I first loaded up the xdf, I was like , but taking what I had already learned and then just going through the xdf and reading parameter comments, I finally got brave enough to try it.
    Not to say I wasnt scared though...lol. I was too chicken to jump in feet first. I went as far as finding a junk 7747, removed the harness plug from it, and sodered the wires from a 7427 directly to it, making a adapter so I could plug in my 7747 harness to the 7427. That way if it didnt work out, I could plug my 7747 back in and still drive it. Well from the first moment I toook it for a test drive with the 7427 I was hooked. NEVER hoooked the 7747 back up, it was that mutch better. I then swapped the pins to the 7427 connector and never looked back.
    79 Jeep Cherokee, AMC 401, T-18 manual trans, hydroboost, 16197427 MPFI system---the toy

    93 Jeep YJ Wrangler, 4.0L, 5 speed, 8.8 rear, homebrew hub conversion and big brakes, hydroboost, 2.5in OME lift, 31x10.50's---the daily driver

    99 Jeep WJ Grand Cherokee limited, 4.0L, auto, 2wd, leather and power everything, 99% stock---the long distance highway ride.

  14. #14
    Fuel Injected! PJG1173's Avatar
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    LOL I jumped in head first... and it still hurts, but I wouldn't use any other.
    87 4Runner, 15" spring lift, 3" body, chevy vortec 355, 5.29 gears, 38.5x15.5x15" Boggers, 280hr, 16168625 running $0D
    93 S10, 12" spring lift, 4.56 gears, F/R lockers, 36x12.5x15 TSL's, long tube headers, 266HR cam, p&p vortec heads, $0D Marine MPFI.
    05 Silverado, 2' lift, 4" exhaust, Bully Dog programmer,

  15. #15
    EFI GearHead ! EagleMark's Avatar
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    Just remember there are 1000 things in $0D compared to 100 things in $42. 90% of both usually don't need to be messed with after you get your fueling and spark in order. So don't let it overwhelm you.

    Now if your motor is built well beyound stock there is more to do...

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
    -= =-

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