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Username Post: IAC on Holley efi system        (Topic#274621)
corvesy 
"2nd Year" Platinum Supporting Member
Posts: 455

Reg: 08-07-08
01-08-12 07:51 AM - Post#2176955    

I have gotten good advice on the site before and need some help. I have a holley efi system using
a custom build sheet metal intake (similar to stealth ram in shape) for my 348 chevy. I am using
the GM ramjet throttle body with the IAC motor that
came with it. The problem is that I can't get the engine to start without opening the throttle body
plate slightly and the engine will not idle below
1000 rpm. I am new at tuning efi's. Is there something I am missing? Thanks

 
Danny Cabral 
Member
Posts: 3411
Danny Cabral
Loc: Ellington, CT
Reg: 11-03-04
01-08-12 08:17 AM - Post#2176968    
    In response to corvesy

  • corvesy Said:
I have a Holley efi system...



Which Holley EFI system do you have?


  • Quote:
The problem is that I can't get the engine to start without opening the throttle body plate slightly and the engine will not idle below 1000 rpm.


Seems like the throttle blades are too far open.
What's the IAC Position when the engine is idling hot?
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 joint steering, 4" lift, 35" tires


 
zwede 
Senior Member
Posts: 1567
zwede
Reg: 01-10-03
01-08-12 08:21 AM - Post#2176969    
    In response to Danny Cabral

The Holley Commander 950 (if that is what you have) requires a Chrysler IAC motor. A GM IAC will not work. The IAC that comes with the Holley kits is from a late 90's pickup with a Magnum V8.
Markus 1971 Vette http://www.corvetteforum.net/c3/zwede


 
corvesy 
"2nd Year" Platinum Supporting Member
Posts: 455

Reg: 08-07-08
01-08-12 08:35 AM - Post#2176974    
    In response to zwede

thanks for the quick reply. My system is the Holley
HP efi. I made sure that the throttle plate was closed all the way but I will verify that. At idle
the computer screen said 0-3 buy it seemed the actual position of the iac plunger was 30% open
thats a guess.

 
Danny Cabral 
Member
Posts: 3411
Danny Cabral
Loc: Ellington, CT
Reg: 11-03-04
01-08-12 08:48 AM - Post#2176979    
    In response to corvesy

  • corvesy Said:
I made sure that the throttle plate was closed all the way but I will verify that.


The throttle blades aren't supposed to be closed all the way.
The idle speed screw is supposed to be set to achieve about 3% IAC Position at hot idle.


  • Quote:
At idle the computer screen said 0-3 buy it seemed the actual position of the IAC plunger was 30% open thats a guess.


What's that mean? We're not guessing at anything...view the Data Monitor.
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 joint steering, 4" lift, 35" tires


 
Dale_Holley 
Member
Posts: 381

Loc: Dallas, TX.
Reg: 11-10-03
01-08-12 08:59 AM - Post#2176986    
    In response to zwede

That's not 100% true. I have used a GM IAC with both C950 and the HP ECU's. You have rewire the harness to fit your application as the GM and Chrysler IAC's connectors are the same and will plug in but are electrically wired different.

 
corvesy 
"2nd Year" Platinum Supporting Member
Posts: 455

Reg: 08-07-08
01-08-12 09:20 AM - Post#2176997    
    In response to Dale_Holley

as I said the data monitor said 0 to 3 fluctuating. My guess was on were the iac plunger was in observing it as it relates to the open air passage cavity. Further info is that I suspected the IAC motor was not working properly and I swapped out a IAC from a LS1 Camaro setting in the driveway and it worked better as for as dropping the idle by 200 rpm but still around 900
rpm and I had to crack the throttle plate to get it to start. Sorry for the guessing statement.






 
Dale_Holley 
Member
Posts: 381

Loc: Dallas, TX.
Reg: 11-10-03
01-08-12 11:15 AM - Post#2177055    
    In response to corvesy

I had problems with my IAC the way it was wired it would close the GM IAC but not open it. I could remove and reinstall the IAC then it would idle down but not be able to open back up to raise the idle back up or control the idle speed small changes. I caused my problems by trying to use the C950 TBI wiring harness (Chrysler IAC) to control modified GM 2BBL TBI IAC. After rewiring the harness it started opening and closing the IAC correctly.

 
zwede 
Senior Member
Posts: 1567
zwede
Reg: 01-10-03
01-08-12 12:10 PM - Post#2177071    
    In response to Dale_Holley

  • Dale_Holley Said:
That's not 100% true. I have used a GM IAC with both C950 and the HP ECU's. You have rewire the harness to fit your application as the GM and Chrysler IAC's connectors are the same and will plug in but are electrically wired different.



Interesting. Thanks for the info, good to know there are more options with a bit of re-wiring.
Markus 1971 Vette http://www.corvetteforum.net/c3/zwede


 
Dale_Holley 
Member
Posts: 381

Loc: Dallas, TX.
Reg: 11-10-03
01-08-12 12:58 PM - Post#2177093    
    In response to zwede

Doug_F pointed me to the C950 wiring diagrams at the back of the install manual for the LT1 harness pin-out.

 
corvesy 
"2nd Year" Platinum Supporting Member
Posts: 455

Reg: 08-07-08
01-23-12 06:15 AM - Post#2182524    
    In response to Dale_Holley

Just a follow-up to my IAC problem. Turns out that
the a and c wires was reversed on the IAC harness connector. I think it was my fault and not holleys.
The IAC and idle work as they should now. Thanks for
the input from the guys that posted. The beast runs
now after several years of planning and work.

Geary

 
OLKY55 
"2nd Year" Gold Supporting Member
Posts: 290
OLKY55
Loc: Fulshear, TX
Reg: 09-18-05
01-23-12 06:56 PM - Post#2182770    
    In response to Dale_Holley

I'm using the Accel remote IAC p/n 74779K. Would anyone know the pinout, or where to find it?
http://www.picturetrail.com/olky55

http://scrides.com/Mayhughpg5.htm

http://scrides.com/mayhugh57.htm

1929 Model A Pickup,Fastburn 385,4X2 EFI
1955 BelAir HT,540,Kinsler EFI Stack
1957 BelAir Seda


 
Dale_Holley 
Member
Posts: 381

Loc: Dallas, TX.
Reg: 11-10-03
01-23-12 08:16 PM - Post#2182798    
    In response to OLKY55

I looked for a instruction set and could not find one. But You can probaby figure it out with a ohm meter. There are two coils inside the IAC.

I originally had my GM IAC wired as a Holley TBI (Chrysler) and it didn't hurt anything. It just didn't want to idle down as it would only open up. I had to rewire it to get it open and close as commanded by the ECU.

Maybe this can help you figure it out. From http://www.megamanual.com/ms2/IAC.htm



 
Danny Cabral 
Member
Posts: 3411
Danny Cabral
Loc: Ellington, CT
Reg: 11-03-04
01-24-12 03:25 AM - Post#2182852    
    In response to OLKY55

  • olky55 Said:
I'm using the Accel remote IAC p/n 74779K. Would anyone know the pin-out, or where to find it?


Look at the wiring schematics in Appendix 13 (end of document, pages 30-36):
http://www.holley.com/data/TechService/Tech nical/1...
It will either be wired like figure 18 (Holley MPI) or figure 22/24 (LS series).



Remember, the IAC connector uses Metri-Pack 150 "pull-to-seat" terminals:
http://whiteproducts.com/pull-to-seat.shtml
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 joint steering, 4" lift, 35" tires


 
corvesy 
"2nd Year" Platinum Supporting Member
Posts: 455

Reg: 08-07-08
01-24-12 06:32 AM - Post#2182886    
    In response to Danny Cabral

just to clarify removing the iac terminal. the tang
that attaches the terminal to the housing is best
depressed from the rear of the terminal and then the
wire pulled forward to release it from the terminal housing. Then if your very skilled you can pry apart
the terminal from the wire, but more than likely you will need new terminal ends as this is small gauge wire.

 
Danny Cabral 
Member
Posts: 3411
Danny Cabral
Loc: Ellington, CT
Reg: 11-03-04
01-24-12 06:56 AM - Post#2182895    
    In response to corvesy

  • corvesy Said:
Just to clarify removing the IAC terminal. The tang that attaches the terminal to the housing is best depressed from the rear of the terminal and then the wire pulled forward to release it from the terminal housing.


Yes, slide out the green wire seal and work from there.
A large sewing needle or a nail (filed flat on one side) works good to depress the tab.
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 joint steering, 4" lift, 35" tires


 
OLKY55 
"2nd Year" Gold Supporting Member
Posts: 290
OLKY55
Loc: Fulshear, TX
Reg: 09-18-05
01-24-12 06:20 PM - Post#2183083    
    In response to Danny Cabral

FYI, according to the ohmmeter, it appears to be an LS style.

Is it me, or is the picture of the connector in the wiring diagram opposite of the schematic? On the schematic, the A is on the top. On the picture of the connector, the A is on the bottom. I have to assume you should follow the schematic.

It is a little hard for my old eyes to see, even with a magnifying glass. Is there a trick to blow up the schematic so us geriatrics can see it?

Thanks for all the help.
http://www.picturetrail.com/olky55

http://scrides.com/Mayhughpg5.htm

http://scrides.com/mayhugh57.htm

1929 Model A Pickup,Fastburn 385,4X2 EFI
1955 BelAir HT,540,Kinsler EFI Stack
1957 BelAir Seda


 
Dale_Holley 
Member
Posts: 381

Loc: Dallas, TX.
Reg: 11-10-03
01-24-12 08:03 PM - Post#2183139    
    In response to OLKY55

If I remember right the schematics are a logical drawing, not a actual pin order that is on the IAC connector. Wire it by the wire color and pin number not by how the picture is shown in the schematic.

 
Danny Cabral 
Member
Posts: 3411
Danny Cabral
Loc: Ellington, CT
Reg: 11-03-04
01-24-12 11:34 PM - Post#2183179    
    In response to OLKY55

  • olky55 Said:
It is a little hard for my old eyes to see, even with a magnifying glass.
Is there a trick to blow up the schematic so us geriatrics can see it?


It's a PDF file.
Mouse: click on the "+" symbol to enlarge the page.
Keyboard: hold down the "Ctrl" key and press the "+" & "-" keys to alter page size.

http://www.holley.com/data/TechService/Tech nical/1...
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 joint steering, 4" lift, 35" tires


 
OLKY55 
"2nd Year" Gold Supporting Member
Posts: 290
OLKY55
Loc: Fulshear, TX
Reg: 09-18-05
01-25-12 07:16 AM - Post#2183250    
    In response to Danny Cabral

Well, I feel a little "inadequate" for not figuring that out.

Interestingly enough, the diagram that comes on the CD comes up in a reader which cannot be zoomed.

Thanks for your help.
http://www.picturetrail.com/olky55

http://scrides.com/Mayhughpg5.htm

http://scrides.com/mayhugh57.htm

1929 Model A Pickup,Fastburn 385,4X2 EFI
1955 BelAir HT,540,Kinsler EFI Stack
1957 BelAir Seda


 
OLKY55 
"2nd Year" Gold Supporting Member
Posts: 290
OLKY55
Loc: Fulshear, TX
Reg: 09-18-05
01-28-12 06:50 PM - Post#2184592    
    In response to Danny Cabral

My connector has the individual seals on each wire. Is there a trick to getting them shoved back in the connector? Do you really need the seals?
http://www.picturetrail.com/olky55

http://scrides.com/Mayhughpg5.htm

http://scrides.com/mayhugh57.htm

1929 Model A Pickup,Fastburn 385,4X2 EFI
1955 BelAir HT,540,Kinsler EFI Stack
1957 BelAir Seda


 
Danny Cabral 
Member
Posts: 3411
Danny Cabral
Loc: Ellington, CT
Reg: 11-03-04
01-29-12 05:05 AM - Post#2184692    
    In response to OLKY55

  • olky55 Said:
My connector has the individual seals on each wire. Is there a trick to getting them shoved back in the connector? Do you really need the seals?


Yes, use the seals. They just need to be pushed into their cavities. A small pocket screwdriver (flat-tip) can be helpful.
Sounds like the cable seals may be the wrong size (they're color-coded for the correct wire gauge).

http://delphi.com/pdf/contact/brochures /DCS_Global... (Metri-Pack 150 series)
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 joint steering, 4" lift, 35" tires


 
OLKY55 
"2nd Year" Gold Supporting Member
Posts: 290
OLKY55
Loc: Fulshear, TX
Reg: 09-18-05
01-29-12 05:40 PM - Post#2184950    
    In response to Danny Cabral

My harness from Holley uses GT150 push-to-seat connectors. The seal is crimped on each wire.
http://www.picturetrail.com/olky55

http://scrides.com/Mayhughpg5.htm

http://scrides.com/mayhugh57.htm

1929 Model A Pickup,Fastburn 385,4X2 EFI
1955 BelAir HT,540,Kinsler EFI Stack
1957 BelAir Seda


 
Danny Cabral 
Member
Posts: 3411
Danny Cabral
Loc: Ellington, CT
Reg: 11-03-04
01-30-12 12:09 AM - Post#2185055    
    In response to OLKY55

  • olky55 Said:
My harness from Holley uses GT150 push-to-seat connectors. The seal is crimped on each wire.


Ah yes, some of the harness connectors are GT 150 series (with the different colored "key index" insert).
The same basic assembly procedure pictured above applies; except the cable seal is lightly crimped on each wire.
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 joint steering, 4" lift, 35" tires


 
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