68wfo
Forum Newbie
Posts: 30

Reg: 11-03-11
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06-08-12 01:45 PM - Post#2234830
I have a very lean stumble from about 1500 to 1700 rpm's especially when I roll into the throttle verrryyy slowly. It starts to stumble at which time I can nearly put the pedal to the floor then when it gets more speed and rpm it kicks in like normal. Datalog shows af ratio is 18.0 I have a copy of the datalog if anyone is interested in taking a look. The car is a '68 Vette with a pro-built 468 6 speed...thanks.
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Danny Cabral
Member
Posts: 3149

Loc: Ellington, CT
Reg: 11-03-04
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06-08-12 02:08 PM - Post#2234837
In response to 68wfo
It's most likely still too lean and may require more timing advance.
Read pages 4-10 of this Edelbrock EFI tuning manual, it's very good:
http://www.edelbrock.com/automotive_new/misc/t ech_...
May God's Grace Bless You
'78 BRONCO: 508" stroker, TFS heads, Dominator MPFI & DIS, A/C, Lentech Strip Terminator AOD, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim-over steering, 4" lift, 35" tires |
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68wfo
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Posts: 30

Reg: 11-03-11
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06-11-12 09:02 PM - Post#2236056
In response to 68wfo
Thanks Danny...I added some timing which seemed to help....And I think I found why I was at 18.0 AFR. For some reason the Co-Pilot program put a 5 in a cell in the idle area. Don't know why but as soon as I changed it to 31 the AFR went richer and comp% was nearly 100. The car when accelerated slowly but steadily feels like it has some flat or surgey areas up to about 2,500 rpm. But if I really lean into the throttle to near max RPM all 600 plus HP come to life and the thing runs like a hell. Where would you start tuning? Do you think the acceleration parameters need tuning?
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Danny Cabral
Member
Posts: 3149

Loc: Ellington, CT
Reg: 11-03-04
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06-11-12 11:34 PM - Post#2236073
In response to 68wfo
Acceleration Enrichment can only be tuned after the Fuel Map is well tuned.
I would learn how to tune it, using the data logger:
http://www.chevytalk.org/fusionbb/showtopic.php?ti...
I think most C950 owners are using this auto tuning software:
http://www.efi101.com/forum/viewtopic.php?t=3857
May God's Grace Bless You
'78 BRONCO: 508" stroker, TFS heads, Dominator MPFI & DIS, A/C, Lentech Strip Terminator AOD, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim-over steering, 4" lift, 35" tires |
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68wfo
Forum Newbie
Posts: 30

Reg: 11-03-11
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06-12-12 07:37 AM - Post#2236159
In response to Danny Cabral
I purchased Tom's software and am using both to see which one works best...any thoughts or comments on which one I should use? As for tuning the fuel map. I have been studying real hard on how to do this. Am I correct in stating that if I see the O2 comp at 125% and the AF at 14 the cell on the fuel map corresponding to the approximate map and rpm should be adjusted (numerically less) for the cell in that area and perhaps the surrounding cells?
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zwede
Senior Member
Posts: 1501

Reg: 01-10-03
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06-12-12 08:51 AM - Post#2236185
In response to 68wfo
Numerically more. Comp of 125% means the ECU is adding fuel because the fuel map is lean.
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68wfo
Forum Newbie
Posts: 30

Reg: 11-03-11
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06-12-12 12:14 PM - Post#2236244
In response to zwede
Thanks...so do I adjust the cells in the approximate area of the map and rpm scale? And by how much?
Edited by 68wfo on 06-12-12 12:15 PM. Reason for edit: No reason given.
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Danny Cabral
Member
Posts: 3149

Loc: Ellington, CT
Reg: 11-03-04
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06-12-12 01:15 PM - Post#2236274
In response to 68wfo
Thanks...so do I adjust the cells in the approximate area of the map and rpm scale? And by how much?
Here are the two relevant posts from the thread I posted above:
http://www.chevytalk.org/fusionbb/showpost.php?pos...
http://www.chevytalk.org/fusionbb/showpost.php?pos...
May God's Grace Bless You
'78 BRONCO: 508" stroker, TFS heads, Dominator MPFI & DIS, A/C, Lentech Strip Terminator AOD, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim-over steering, 4" lift, 35" tires |
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68wfo
Forum Newbie
Posts: 30

Reg: 11-03-11
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06-13-12 07:29 AM - Post#2236580
In response to Danny Cabral
Thanks Danny...I am considering removing my O2 sensor because I don't know how old it is and if it might have carbon buildup. Do you know what I can use ie...alcohol, mineral spirits etc...
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Danny Cabral
Member
Posts: 3149

Loc: Ellington, CT
Reg: 11-03-04
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06-13-12 08:39 AM - Post#2236618
In response to 68wfo
I've never tried cleaning an oxygen sensor, nor would I use any chemicals either.
http://www.bosch.com.au/content/language1/down load...
May God's Grace Bless You
'78 BRONCO: 508" stroker, TFS heads, Dominator MPFI & DIS, A/C, Lentech Strip Terminator AOD, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim-over steering, 4" lift, 35" tires |
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68wfo
Forum Newbie
Posts: 30

Reg: 11-03-11
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06-13-12 12:13 PM - Post#2236709
In response to zwede
Can you tell me how you determine mathematically what the number or value in the fuel cell should be? Let's say I have a lean condition at a specific map and rpm and the cell number is 60. How do I determine what the correct value should be? I know it should be higher but how much higher?
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Danny Cabral
Member
Posts: 3149

Loc: Ellington, CT
Reg: 11-03-04
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06-13-12 03:10 PM - Post#2236771
In response to 68wfo
Record a short steady state data log.
Locate the cell by intersecting the MAP & RPM values.
At that point, look at the "O2 Mod" percentage.
100% is the baseline, the ECU wasn't adding or subtracting fuel.
Anything over 100%, the ECU was adding that fuel (too lean).
Anything under 100%, the ECU was subtracting that fuel (too rich).
Using cell value 60 for example, with an O2 Mod of 115% (too lean);
60 (Fuel Map cell value) + 15% (O2 Mod) = 69 new Fuel Map cell value.
If the O2 Mod is under 100%, you would simply subtract the percentage.
After tuning the specific cells, enter the Fuel Graph, and blend the
surrounding areas to those tuned cells. Smooth over the entire graph.
Do this until the data logs indicate a consistent 95%-100% O2 Mod.
Of course, ensure your Target Air/Fuel Ratio Map is programmed to your liking.
May God's Grace Bless You
'78 BRONCO: 508" stroker, TFS heads, Dominator MPFI & DIS, A/C, Lentech Strip Terminator AOD, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim-over steering, 4" lift, 35" tires |
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Danny Cabral
Member
Posts: 3149

Loc: Ellington, CT
Reg: 11-03-04
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06-14-12 02:25 AM - Post#2236964
In response to Danny Cabral
Here's the entire C950 Fuel Map tuning procedure (using the Data Logger),
collectively in one post, for others who may be searching for it:
Especially for tuning purposes, I would:
A) Set the 'Max TPS for Closed Loop Operation' at two numbers higher than your 'WOT TPS Position'. You don't want any chance of the TPS value moving slightly over the wide open throttle value, and entering open loop (due to thermal expansion, flexing, etc).
B) Set ALL the 'O2 Compensation Limits (%)' to 25. This will allow the ECU to do the most it can, and give you a greater range of tuning calculation. When you start tuning the Fuel Map, that preset 15% will limit the ECU's compensation range, and you'll be wondering how much more the ECU would've corrected the Fuel Map (necessitating the need for more data logs).
This will set the ECU in constant closed loop mode, allowing you to data log (O2 Mod), and tune the Fuel Map based on the ECU's corrections (Closed Loop Compensation). In other words, let the ECU tell you which direction to tune, and how much. Of course, this requires a good Target Air/Fuel Ratio Map.
Use the data log's O2 Mod, MAP & RPM to tune the Fuel Map by adding (rich) or subtracting (lean) the O2 Mod's percentage from each cell. Use a calculator, and don't tune the same cell twice. Locate the Fuel Map cell you want to tune by intersecting the horizontal MAP value, and the vertical RPM value's axis point. You're finding the MAP & RPM axis values from the data log, and applying them to the Fuel Map. You'll need to do this many times by scrolling along the data log, and changing Fuel Map cell numbers.
Afterwards, the Fuel Graph needs to be smoothed out. Be conservative because adjusting the Fuel Graph actually changes the Fuel Map tuning (cell numbers). It should look like the example on page 35 of the C950 manual (and even that one could be a bit smoother). Study the shape (curve) of the Fuel Graph...it's that way for a good reason because it matches the torque curve of the engine; not the horsepower curve. (Make sure you also understand the 'graphical representation' of the Fuel Map/graph on page 31.) Read this link for more information on feeding the engine's torque curve: http://www.chevytalk.org/fusionbb/showtopic.php?ti...
You can do all of this on your home PC at you leisure. If you need further instruction on the mathematical calculations (O2 Mod % from the data log), and how to apply them to the Fuel Map, see below.
Record a short steady state data log.
Locate the cell by intersecting the MAP & RPM values.
At that point, look at the "O2 Mod" percentage.
100% is the baseline, the ECU wasn't adding or subtracting fuel.
Anything over 100%, the ECU was adding that fuel (too lean).
Anything under 100%, the ECU was subtracting that fuel (too rich).
Using cell value 60 for example, with an O2 Mod of 115% (too lean);
60 (Fuel Map cell value) + 15% (O2 Mod) = 69 new Fuel Map cell value.
If the O2 Mod is under 100%, you would simply subtract the percentage.
After tuning the specific cells, enter the Fuel Graph, and blend the
surrounding areas to those tuned cells. Smooth over the entire graph.
Do this until the data logs indicate a consistent 95%-100% O2 Mod.
Of course, ensure your Target Air/Fuel Ratio Map is programmed to your liking.
After tuning the Fuel Map, the O2 Compensation Limits % should be decreased in the high load/full throttle areas. So if you have a wideband O2 sensor error/failure, the engine can still run fairly well (without the ECU modifying 25% of the fueling). Change to Open Loop mode until you can replace the O2 sensor. If you start tuning without the full 25% O2 Compensation, it will require you to perform more data logging because a new Fuel Map will need more than a "minimum" amount of tuning. Keep in mind, I'm talking about temporary settings for initial tuning purposes (with a new C950/wideband system).
There is an exception, when you can decrease the O2 Compensation Limits, from the start: If you used the C950 'Map Builder' Excel program (C950CALC in C:drive software) accurately, then your base map should be fairly close, and won't require an excessive amount of O2 Compensation when tuning. Use the C950 'Map Builder' program first for WOT, blend the Fuel Graph next, and then begin tuning (you'll be smoothing the Fuel Graph again after each data log/tuning session).
I'd like to add some necessary information to my aforementioned 'data log tuning' procedure.
When applying the data log changes to the Fuel Map, only make changes from the 'steady-state' periods of the data log. In other words, when reviewing the data log, focus on the areas where you were not accelerating. During acceleration, the base map is modified by adding the 'transient fuel' (acceleration enrichment) parameters. If you tune the Fuel Map during these transient fueling periods, the base Fuel Map will end up being overcompensated. (Acceleration enrichment can't be tuned until the base Fuel Map is steady-state tuned.)
The key here is to look at the green RPM line on the data log. For initial Fuel Map tuning purposes, ignore the diagonally upward periods - transient fueling. As a matter of fact, I usually only select the green RPM line for simplicity. Read the O2 Mod's % value during flat horizontal (steady-state) periods of the data log. If in doubt, verify that the TPS and/or MAP values are not increasing. Continue to tune those Fuel Map cells by intersecting the horizontal MAP & vertical RPM axis points (MAP & RPM points acquired from data log). At 4000+ RPM, acceleration enrichment is virtually nonexistent, so the task becomes easier. At 4000 RPM & higher, just read and tune directly off of every point on the data log.
Knowing how to drive for data logging purposes is especially useful, and will ease your tuning task.
First, I like to record short data logs. This will lessen the chance of tuning the same Fuel Map cell twice, and the data log will look less daunting. Second, since the objective is to steady-state tune, avoid a lot of acceleration (or do it as quickly as possible). I like to start by recording several seconds of idling (neutral), in gear and with the A/C on too. Then in 1st gear, hold the RPM steady for several seconds according to each RPM point on your Fuel Map. Repeat this process for each number of gears/speeds your transmission has (overdrive will be recorded on the highway only). In other words, you'll be doing this many times for each gear and RPM point. Smooth the Fuel Graph after each tuning session.
A good example of a second data log would be repeating this entire procedure going uphill or at some points, gently applying the brakes to reach higher MAP load points. (Better yet, if you can get your vehicle stuck in the mud or snow, you can use this to substitute a 'rolling road'...don't laugh, it works.)
Lastly, for initial tuning purposes, I would disable the 'decel fuel cutoff' function by enter 9000 RPMs, otherwise it will correctly indicate a maximum lean 18:1 air/fuel ratio, preventing you from tuning some deceleration points of the Fuel Map. Ideally, the entire fuel map should be tuned to 95-100% Closed Loop Compensation.
May God's Grace Bless You
'78 BRONCO: 508" stroker, TFS heads, Dominator MPFI & DIS, A/C, Lentech Strip Terminator AOD, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim-over steering, 4" lift, 35" tires |
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68wfo
Forum Newbie
Posts: 30

Reg: 11-03-11
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06-14-12 07:54 AM - Post#2237038
In response to Danny Cabral
Thanks Danny...does it make sense to have the value on the modifiers screen set to 100% so there is modification to the steady state values while logging data?
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Danny Cabral
Member
Posts: 3149

Loc: Ellington, CT
Reg: 11-03-04
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06-14-12 08:19 AM - Post#2237050
In response to 68wfo
Thanks Danny...does it make sense to have the value on the modifiers screen set to 100% so there is modification to the steady state values while logging data?
Sure...they're most likely already at 100% at normal operating temperature (180°F).
May God's Grace Bless You
'78 BRONCO: 508" stroker, TFS heads, Dominator MPFI & DIS, A/C, Lentech Strip Terminator AOD, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim-over steering, 4" lift, 35" tires |
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68wfo
Forum Newbie
Posts: 30

Reg: 11-03-11
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06-14-12 08:24 AM - Post#2237052
In response to Danny Cabral
The previous owner has the air temp modifier settings at 95%, AE correction vs. Coolant temp at 78.1% and AE correction vs. TPS at 125. Rate of change for the MAP sensor is 70, 60, 50, 46,46,50,55,60,65,70,75,7 5,75,75,75,75.
Does this look correct?
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Danny Cabral
Member
Posts: 3149

Loc: Ellington, CT
Reg: 11-03-04
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06-14-12 08:40 AM - Post#2237055
In response to 68wfo
Does this look correct?
This thread should answer those questions:
http://www.chevytalk.org/fusionbb/showtopic.php?ti... (Read the entire thread.)
May God's Grace Bless You
'78 BRONCO: 508" stroker, TFS heads, Dominator MPFI & DIS, A/C, Lentech Strip Terminator AOD, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim-over steering, 4" lift, 35" tires |
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68wfo
Forum Newbie
Posts: 30

Reg: 11-03-11
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06-14-12 08:51 AM - Post#2237058
In response to Danny Cabral
It does however my MAP numbers that are already set look way off to me based on the info I read. I have a 468 Chevy big block with a moderately radical cam. Can you give me your opinion on what I should do with the MAP values? I don't know where to start with them...thanks!
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Danny Cabral
Member
Posts: 3149

Loc: Ellington, CT
Reg: 11-03-04
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06-14-12 09:05 AM - Post#2237059
In response to 68wfo
Can you give me your opinion on what I should do with the MAP values? I don't know where to start with them...thanks!
Did you read the paragraph under "Rate of Change of MAP Sensor"?
May God's Grace Bless You
'78 BRONCO: 508" stroker, TFS heads, Dominator MPFI & DIS, A/C, Lentech Strip Terminator AOD, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim-over steering, 4" lift, 35" tires |
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68wfo
Forum Newbie
Posts: 30

Reg: 11-03-11
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06-14-12 09:17 AM - Post#2237069
In response to Danny Cabral
I did "more potent big blocks need about 15 Slow end". My settings start at 70...I guess I am a little tentative in making such a large change. Based on your experience should I make that change to the MAP values based on the write up you provided? I don't want to damage the motor.
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zwede
Senior Member
Posts: 1501

Reg: 01-10-03
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06-14-12 09:25 AM - Post#2237074
In response to 68wfo
Is your system TBI or MPFI?
I have the C950 MPFI on a 454 BBC (in a C3 vette, BTW). I have to run VERY low AE vs MAP values to avoid drowning the engine. single digits to the left, about 25 to the right.
But I'm told TBI requires larger values.
This also depends on the size of your injectors. Small injectors would need higher values. My injectors are 42 lbs/hr.
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68wfo
Forum Newbie
Posts: 30

Reg: 11-03-11
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06-14-12 09:29 AM - Post#2237077
In response to zwede
MPFI...I believe it has 42lb's as well. I have looked at your file from 2003 and incorporated some of the settings. I am concerned as to why the settings I have look so far off. The guy I bought the car from said the shop that installed the system "knew" what they were doing. But when I look at the settings they made I have to wonder if they had any clue. All this help is greatly appreciated. I want to get this car reliable and on the road...
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Danny Cabral
Member
Posts: 3149

Loc: Ellington, CT
Reg: 11-03-04
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06-14-12 09:34 AM - Post#2237082
In response to 68wfo
I guess I am a little tentative in making such a large change. Based on your experience should I make that change to the MAP values based on the write up you provided? I don't want to damage the motor.
You're doing more damage now, with excessively rich Acceleration Enrichment settings (fuel washing cylinder walls)!
You have to actually drive the vehicle, and determine what it needs. Of course the previous owner "didn't have a clue".
May God's Grace Bless You
'78 BRONCO: 508" stroker, TFS heads, Dominator MPFI & DIS, A/C, Lentech Strip Terminator AOD, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim-over steering, 4" lift, 35" tires |
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68wfo
Forum Newbie
Posts: 30

Reg: 11-03-11
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06-14-12 04:47 PM - Post#2237201
In response to Danny Cabral
Danny...I am working on implementing your suggestions...what parameter can I change that will reduce the motor revving up on start up. It goes to nearly 2,000 rpm's after I let it sit for a few minutes then goes to idle.
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Danny Cabral
Member
Posts: 3149

Loc: Ellington, CT
Reg: 11-03-04
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06-15-12 02:36 AM - Post#2237309
In response to 68wfo
What parameter can I change that will reduce the motor revving up on start up. It goes to nearly 2,000 RPMs after I let it sit for a few minutes then goes to idle.
Ensure the first three or four "Minimum IAC Position" values are zero:
www.chevytalk.org/fusionbb/showtopic.php?tid/15435...
Ensure you're running the latest firmware:
http://www.chevytalk.org/fusionbb/showpost.php?pos...
If it's a momentary high idle, immediately after starting, decrease the IAC Parked Position.
If it remains high, but gradually slows down as coolant temperature increases, adjust the IAC Desired Idle.
Also, are the throttle blades properly set (idle speed screw on throttle body) to achieve an IAC Position of 10-15 counts (Data Monitor on Fuel Map) when the engine is fully warmed up?
May God's Grace Bless You
'78 BRONCO: 508" stroker, TFS heads, Dominator MPFI & DIS, A/C, Lentech Strip Terminator AOD, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim-over steering, 4" lift, 35" tires |
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68wfo
Forum Newbie
Posts: 30

Reg: 11-03-11
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06-15-12 07:26 AM - Post#2237374
In response to Danny Cabral
Firmware upgraded by Holley...high idle is temporary so I think it may be the AIC parked position. I will give it a try...thanks.
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Danny Cabral
Member
Posts: 3149

Loc: Ellington, CT
Reg: 11-03-04
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06-15-12 09:27 AM - Post#2237406
In response to 68wfo
High idle is temporary, so I think it may be the IAC parked position.
Both of the high idle scenarios are "temporary".
Ensure you're adjusting the correct parameter.
May God's Grace Bless You
'78 BRONCO: 508" stroker, TFS heads, Dominator MPFI & DIS, A/C, Lentech Strip Terminator AOD, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim-over steering, 4" lift, 35" tires |
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68wfo
Forum Newbie
Posts: 30

Reg: 11-03-11
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06-15-12 10:02 AM - Post#2237416
In response to Danny Cabral
What I mean by temporary is it only last about 2 seconds after starting then goes to the correct idle. I will try lowering the park position. It is set at 55 at normal operating temp. How much should I try lowering the by...5, 10 ?
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zwede
Senior Member
Posts: 1501

Reg: 01-10-03
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06-15-12 11:02 AM - Post#2237440
In response to 68wfo
If your throttle blades are set correctly, your IAC count at hot idle should be very low, around 10. If so, a parked position of 30 would be a good starting point.
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68wfo
Forum Newbie
Posts: 30

Reg: 11-03-11
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06-15-12 11:03 AM - Post#2237441
In response to zwede
Thanks ... I will try that and report back...
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