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Thread: Idle tuning

  1. #1
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    Idle tuning

    So Iíve had a high idle for sometime and have changed the idle settings in the Xcal, set the TPS, and manually adjusted the Accufab single blade a few times over the years and have only achieved a drop from 1,250 to right around 1,000 (970 to 1130ish on the data log).

    Itís spring time which means itís that time of the year I donít mind messing around with it a bit before I get burned out even thinking about working on the car. So I spent the last hour or so starting fresh with adjustments. First I warmed her up with a drive, then set idle in park and neutral settings to 690 & 694, then I removed the IAC but left it plugged in and duct taped the inlet/outlet shut and manually adjusted the single blade easily down to around 700 or so. Then I reset the TPS to as close to .98 as possible (ended up at .95), re installed the IAC and let her run for 10 minutes to relearn.

    Zero change. I tried two other known to be good IACs with same results, even swapped in a new gasket. So I started data logging RPMs and never noticed before RPMs demanded and I see the demanded is locked in at 992 even though I set it to 690?? That makes sense as my idle bounces between 970 and 1030 give or take. Sheís always had a small bit of a choppy idle, nothing new there.

    So am I fighting a lost cause? If I canít reduce the demanded idle down (even though I have in settings) then the IAC will always be bouncing to achieve that 992 RPM. I never caught this PID in data logging before and I wanted to make sure Iíve done everything on my end and Iím not missing something here before I bother Marty and Jeff.

    Iím ultimately trying to cure a bad part throttle bucking trying to maintain speed in and out of pedal at anything under 35/40 in any gear then every gremlin has been fixed. It takes a seriously steady right foot to acquire any form of smooth and a left foot on standby to quickly clutch it to smooth it out. Seriously annoying in traffic or even in my subdivision.

    But hey, I did get my constant running fan fixed this year! Thatís 1 of my only 3 complaints. That fix was 33% of my struggles!


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    Cobra short block / ProCharger F1-A / Cog drive upgrade / Manley valves / Brian Tooley Racing valve springs / 80# inj. / -8 fuel line / -6 return / Aeromotive 340 pumps and regulator / 2012 GT500 TR6060 six speed / twin disc clutch / Driveshaft Shop GT500 upgraded CV joint shaft / BA5000 blow thru MAF/ 4.10's / Ford Racing 31 spline set up and Girdle / Metco D.S. safety loop / Stainless Works headers, cats, and everything else out back / ClassGlass hood / Bob's hood strut mod / Hurst line lock / Metco control arms / Addco front and rear sway bars / Monroe severe duty shocks all around / Race concepts rotors / Badgeless grille / 35% tint / FBM's interior LED kit and ambient lighting kit / Pioneer FB700 deck / kenwood speaker 4 Ch. / Rockford Fosgate 10" sub and amp / Kicker 6 X 8's all around / back up cam / bluetooth / Pioneer Xm / 704 RWHP 603 RWTQ tuned by Mo's Speedshop.

  2. #2
    Join Date
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    Similar challenges here on my 40 year older car. For the first time this spring since I've owned the car I have the stock jets in it. It has always idled high and I was talking about it with a mechanic friend the other day. Book says idle speed is 675-700. When I get everything (timing, fuel) adjusted where it runs best it idles about 1,100. I have to starve it for fuel to get it down to 900, and if I go lower than that it idles erratically. Idles pretty darn well at 900, so there we go.
    1963 Marauder S-55, Super Marauder 406
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    #168

  3. #3
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    What are you setting the xcal rpm idle at? Does that make any difference say set at 600 or 1200?
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  4. #4
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    Quote Originally Posted by kirk View Post
    Similar challenges here on my 40 year older car. For the first time this spring since I've owned the car I have the stock jets in it. It has always idled high and I was talking about it with a mechanic friend the other day. Book says idle speed is 675-700. When I get everything (timing, fuel) adjusted where it runs best it idles about 1,100. I have to starve it for fuel to get it down to 900, and if I go lower than that it idles erratically. Idles pretty darn well at 900, so there we go.
    Look for excessive play in the throttle shaft, twisted throttle shaft causing 1 to close but holding other 1 slightly open or bent throttle blades. Any of these will cause uncontrollable idle speed.

    WLB
    BB#1) 1996 ImpalaSS - 16,500 miles - 100% stock
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  5. #5
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    Quote Originally Posted by Turbov6Bryan View Post
    What are you setting the xcal rpm idle at? Does that make any difference say set at 600 or 1200?
    Like mentioned I set it at 690. I also tried 544 for grins, zero difference.


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    Cobra short block / ProCharger F1-A / Cog drive upgrade / Manley valves / Brian Tooley Racing valve springs / 80# inj. / -8 fuel line / -6 return / Aeromotive 340 pumps and regulator / 2012 GT500 TR6060 six speed / twin disc clutch / Driveshaft Shop GT500 upgraded CV joint shaft / BA5000 blow thru MAF/ 4.10's / Ford Racing 31 spline set up and Girdle / Metco D.S. safety loop / Stainless Works headers, cats, and everything else out back / ClassGlass hood / Bob's hood strut mod / Hurst line lock / Metco control arms / Addco front and rear sway bars / Monroe severe duty shocks all around / Race concepts rotors / Badgeless grille / 35% tint / FBM's interior LED kit and ambient lighting kit / Pioneer FB700 deck / kenwood speaker 4 Ch. / Rockford Fosgate 10" sub and amp / Kicker 6 X 8's all around / back up cam / bluetooth / Pioneer Xm / 704 RWHP 603 RWTQ tuned by Mo's Speedshop.

  6. #6
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    Vacuum leak will cause high idle, any possibility of that Bob?

    Vacuum Leak: On any engine, a vacuum leak will cause a high engine idle as the oxygen sensor detects lean operation and the engine computer then tries to compensate, which can result in abnormal idle

    WLB
    BB#1) 1996 ImpalaSS - 16,500 miles - 100% stock
    ______________________________ ___________

    BB#2) 2003 Marauder (300a) - 34k miles - Daily Driver
    #2912 of 7093
    Conceived 8/6/2002
    Delivered 9/19/2002
    Adopted 8/10/2011
    Trilogy 242 - Self Installed 9/9/12 (0-60 5.5 sec)
    Pioneer 6x8 Front
    Legacy 600w 6x9 Rears
    JL 6.5 SubWoofer
    K&N CAI
    Window tint 50% rear/35% front
    FBM CHMSL with Strobe mod 7/1/12
    DR Deep Aluminum Trans Pan
    Sparta FOMOCO Racing 8.8 Girdle
    Mo's Dyno Tune
    Gorilla Nuts - The System
    Ford Racing 4.10s, 31 spline Cobra carrier & axles 7/1/12
    Powder Coat Axle Housing 7/1/12
    CME HP Rear Control Arms & Watts Link 7/1/12
    ______________________________ ________________

    Rex "SC Cheesehead" Weinbender 11-14-13
    Ed "Baaad GN" Linthicum 8-6-2014

  7. #7
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    Quote Originally Posted by MyBlackBeasts View Post
    Vacuum leak will cause high idle, any possibility of that Bob?

    Vacuum Leak: On any engine, a vacuum leak will cause a high engine idle as the oxygen sensor detects lean operation and the engine computer then tries to compensate, which can result in abnormal idle
    None. Like I said, I can easily achieve a low idle when the IAC is removed from the equation running on the throttle body alone. I mean technically I could make it not even run if I wanted. I guess I just need to make the call to Jeff as I canít do anything about the demanded RPM value.


    Sent from my iPhone using Tapatalk Pro


    Cobra short block / ProCharger F1-A / Cog drive upgrade / Manley valves / Brian Tooley Racing valve springs / 80# inj. / -8 fuel line / -6 return / Aeromotive 340 pumps and regulator / 2012 GT500 TR6060 six speed / twin disc clutch / Driveshaft Shop GT500 upgraded CV joint shaft / BA5000 blow thru MAF/ 4.10's / Ford Racing 31 spline set up and Girdle / Metco D.S. safety loop / Stainless Works headers, cats, and everything else out back / ClassGlass hood / Bob's hood strut mod / Hurst line lock / Metco control arms / Addco front and rear sway bars / Monroe severe duty shocks all around / Race concepts rotors / Badgeless grille / 35% tint / FBM's interior LED kit and ambient lighting kit / Pioneer FB700 deck / kenwood speaker 4 Ch. / Rockford Fosgate 10" sub and amp / Kicker 6 X 8's all around / back up cam / bluetooth / Pioneer Xm / 704 RWHP 603 RWTQ tuned by Mo's Speedshop.

  8. #8
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    I wonder why the computer won't accept your input? Are you remembering to hit ENTER after you set the new numbers? Is the area around where the TB blade seals nice and clean and not being slightly held open by some grit. Just spitballin' I don't know. Have Melonie look at it, it might amaze you how innocently perceptive a non-mechanic eye can be when it comes to gremlins. She might see a loose wire or something.

  9. #9
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    What voltages are you getting at the iac sensor while running?
    The twins2.3 whipple/aluminatorVortech V-2 lots of goodies

    04 DTR totaled, might make into a station wagon Here is how bad it was https://youtu.be/REUxjP1BVpg

    04 Silver Birch Dark Charcoal Hardtop Whipple
    04 Silver Birch Dark Charcoal Hardtop V2
    04 Silver Birch Light Flint To Dark Charcoal Converted
    03 DD Blue / Light Flint
    03 Blue / Dark Charcoal #232
    03 Silver Birch Light Flint <--- Cannot kill it.
    03 Black 300a

    04 Heaton Swapped DTR
    Joe's Wrecked DTR rebuild thread

  10. #10
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    Idle tuning

    Quote Originally Posted by Turbov6Bryan View Post
    What voltages are you getting at the iac sensor while running?
    After a good warm up sheís at 7.65 and 53% duty cycle.

    I even set the target RPM to 344 Park/440 Neutral for giggles and still get the desired RPM on data log to show 992. Still hovering right at that..

    It appears that although it seems to be unlocked for adjustment in fact it isnít and everything is acting like it should be. Maybe somebody could datalog their desired rpm (rpmdsd) PID compared to their RPM PID (rpm) to give me something to go on?


    Sent from my iPhone using Tapatalk Pro


    Cobra short block / ProCharger F1-A / Cog drive upgrade / Manley valves / Brian Tooley Racing valve springs / 80# inj. / -8 fuel line / -6 return / Aeromotive 340 pumps and regulator / 2012 GT500 TR6060 six speed / twin disc clutch / Driveshaft Shop GT500 upgraded CV joint shaft / BA5000 blow thru MAF/ 4.10's / Ford Racing 31 spline set up and Girdle / Metco D.S. safety loop / Stainless Works headers, cats, and everything else out back / ClassGlass hood / Bob's hood strut mod / Hurst line lock / Metco control arms / Addco front and rear sway bars / Monroe severe duty shocks all around / Race concepts rotors / Badgeless grille / 35% tint / FBM's interior LED kit and ambient lighting kit / Pioneer FB700 deck / kenwood speaker 4 Ch. / Rockford Fosgate 10" sub and amp / Kicker 6 X 8's all around / back up cam / bluetooth / Pioneer Xm / 704 RWHP 603 RWTQ tuned by Mo's Speedshop.

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