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Thread: In gear low idle problem please help

  1. #1
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    In gear low idle problem please help

    I have an ongoing issue that seemed sporatic to begin with and now is almost constant. Seems to do it more when warmed than cold.. 2002 6.0 tx giant cam ,turbocharged, 4l60e 2800 vigilante stall in a 70 chevelle.
    Ive drilled the tb hole to bring down iac counts as well as tb screw as been adjusted. Im exhausting my thoughts on this and dont now what else to do. Please look at my tune and log and let me know what is going wrong here.

    Looks like everything is working right afr and timing is stable until the iiac tries to steadily compensate for the low idle issue.
    There is no maf or o2's on this setup and is 2bar.
    Attached Files Attached Files
    1970 Chevelle 02 6.0L , 2Bar SD, 60lb , TX Giant, T76
    1971 Chevelle 04 5.3L ,45lb , T70
    1998 Blazer 99 6.0L , Mild Cam

  2. #2
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    If you look at the trans out rpm you can see when i put it in gear and then the idle gets unstable and the iac steadily rises till its maxed. motor doesnt sound right when this happens...probally from the leaning out. im at a dead end and dont understand whatese to do.
    1970 Chevelle 02 6.0L , 2Bar SD, 60lb , TX Giant, T76
    1971 Chevelle 04 5.3L ,45lb , T70
    1998 Blazer 99 6.0L , Mild Cam

  3. #3
    Advanced Tuner blownbluez06's Avatar
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    You have more idle advance than I see most cams operate well at. You have almost 0 overspeed/underspeed in your tables. I would recommend moving back toward the direction of stock on those. You are also so lean that it is unable to sustain RPM. You are in open loop so the only "out" that you're giving it to recover is opening the IAC since you've basically locked out the spark and fuel.
    With SD tuning, you need to go closed loop if possible because you hit certain VE values with a different load and it requires different fueling. You end up finding a happy medium in the VE and let the STFT's adjust accordingly.
    Last edited by blownbluez06; 05-22-2013 at 08:57 AM.
    Hsquared racing engines RHS 427, Procharger F2, Moran Billet Atomizer injectors, Alky Control,Mast LS7 heads, Nitrous outlet kit,Tilton quad disc clutch, DSS shaft, RKT56 ZR1 trans, RPM Quaife diff. Built and tuned by yours truly.

  4. #4
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    Thanks for the response blownbluez06. I was trying to get the lowest map value possible with this cam in idle. I lowered it by 2 degrees.
    I initially was getting really erratic timing in idle and had lowered those under and overspeed tables to compensate. I now have put in the stock values and halved them.

    And i also added some fuel in the areas where the iac was compensating for the idle.

    When i did the harness i pulled all the o2s and emissions stuff out. If keeping the fueling stable is going to be an ongoing problem in open loop , i might just break down and add the o2 sytem back in to the setup.
    Well i hope this helps the issue im having and thank you for the help. i sure hope i can get this nailed down without the 02s.
    1970 Chevelle 02 6.0L , 2Bar SD, 60lb , TX Giant, T76
    1971 Chevelle 04 5.3L ,45lb , T70
    1998 Blazer 99 6.0L , Mild Cam

  5. #5
    Advanced Tuner blownbluez06's Avatar
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    The timing is supposed to be erratic at idle. That's how it works and it's the quickest acting controls you have to keep your idle stable. Nothing else works that quickly, not the ETC, IAC or the fueling adaptives. Having high timing to achieve max vacuum isn't the best course because you don't leave any headroom for the over/underspeed tables to work. For shits and giggles, try 21 degrees timing and stock values in the overspeed/underspeed tables some time with your fueling in the low 15's:1 and see how it acts.
    Hsquared racing engines RHS 427, Procharger F2, Moran Billet Atomizer injectors, Alky Control,Mast LS7 heads, Nitrous outlet kit,Tilton quad disc clutch, DSS shaft, RKT56 ZR1 trans, RPM Quaife diff. Built and tuned by yours truly.

  6. #6
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    After doing everything mentioned ive been adding more and more fuel to the 90to100kpa between 400 and 800 rpm and have gotten it allot better but now have constant problems with the idle dipping.
    Now get this.. i noticed today that when i mash the brakes ..it starts idling down more and more and motor starts leaning out.

    Ive double checked the wiring for the brake switch for the tcc and all is good.. i dont see any major voltage drop But i do have the high amp alternatOr so maybe it drags the motor down more?!? Idk whats going on.
    This is a manual brake setup so no vacuum related components are an issue. Car seems to run allot better with my older tune still idles down but no where near as bad so i dont understand qhat in the tune is related.
    Last edited by lt170chevelle; 05-30-2013 at 08:46 AM.
    1970 Chevelle 02 6.0L , 2Bar SD, 60lb , TX Giant, T76
    1971 Chevelle 04 5.3L ,45lb , T70
    1998 Blazer 99 6.0L , Mild Cam

  7. #7
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    Injector voltage offset maybe wrong?? I believe its stock paremeters
    1970 Chevelle 02 6.0L , 2Bar SD, 60lb , TX Giant, T76
    1971 Chevelle 04 5.3L ,45lb , T70
    1998 Blazer 99 6.0L , Mild Cam

  8. #8
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    possible vacuum leak !!!!! at 900 to 1000 rpm and 90kpa on map . in gear or out should not go that high . 850-950 rpm 50-60 kpa park or neutral 60 to 65 in drive . or possible wrong map sensor . try to log injector ms on scanner also to see what the injectors are doing hth

  9. #9
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    Update.. found out there is a direct relation to the tcc brake switch Feed and my problem. Everytime i push the brake it opens the tcc curcuit and the Idle steadily drops. I bypassed the switch temporarily To keep lockup on highway..idles great now at everystop Besides a little surge when hot..
    Ive yet to find a related table to the tcc brake switch feed But am very happy to have narrowed it down.
    Oh this cam is very healthy and with the turbo it isnt going to see much vaccum idling imo. Definitely no vac leaks Though.
    Now just got to figure out what the pcm is doing when the tcc brake switch is actuated.
    Last edited by lt170chevelle; 05-30-2013 at 02:03 PM.
    1970 Chevelle 02 6.0L , 2Bar SD, 60lb , TX Giant, T76
    1971 Chevelle 04 5.3L ,45lb , T70
    1998 Blazer 99 6.0L , Mild Cam

  10. #10
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    Ive also narrowed my idle surge down to too much fueling in idle. This cam needs a 16.5 afr in idle to idle evenly. Also Im getting better vaccum with it running smoother and 28 degrees of advance in idle.
    Thanks for everybodies help on diagnosing these issues.
    1970 Chevelle 02 6.0L , 2Bar SD, 60lb , TX Giant, T76
    1971 Chevelle 04 5.3L ,45lb , T70
    1998 Blazer 99 6.0L , Mild Cam