Holly HP EFI-- Idle & IAC Tuning
 

Anyone have some decent pointers and/or starting points on how to improve start up and idle on a Holley HP system on a 88 Ford 302 using the stock Ford IAC? We've had this deal on the car a couple years now and the drivability down the track has been great.. starting it to get there and sometimes stalling it up smoothly has been inconsistent to terrible to say the least. I've done some research but I just don't know enough to put it all together and make the car happy.

Any help or pointers would be great.

Thanks
Brad

Re: Holly HP EFI-- Idle & IAC Tuning
 

Nobody has spoke up so I'll try to help a little. I have a dozen or so tunes in class cars and have gotten completely away from using the IAC.I tried using mine in my personal car, but it has more disadvantages than advantages. I used a IAC all one summer and I think they are a waste of time. Its hard to keep them from surging around with the camshafts we use. And I don't see why its needed? It's just one other thing to mess with. If using the Holley, "uncheck/disable" the IAC in your settings and work on your idle/off idle areas a little ..

Re: Holly HP EFI-- Idle & IAC Tuning
 

Just like Jeff said, we completely disabled the IAC and left it unplugged, had the same issue with the same 5.0 stock combo, we were using an Accel DFI system back then, shouldn't matter though, we turned the idle screw up on the throttle body and took care of it, idled a little high but we didn't mind.





Bret Velde
2003 ??/SA

Re: Holly HP EFI-- Idle & IAC Tuning
 

Yep, Brother Niceswanger is not just another pretty face.
Agree 100% with his comments.
No need for IAC, and in fact nothing but problems with IAC and the cams we run in these class combinations.
Either remove the IAC and block it off, or make sure its in the fully closed position then unplug it and leave it unplugged. Then work the throttle blade stop setscrew like the old days to set the idle RPM, and then tweak the fuel map in that range for a nice clean idle, and crisp off idle smacks.

Easy peazy and no surprises with hunting/surging, overshoot, stalling as you try to make your way to the lanes with an iced-up intake for class when your IAC is going nuts because of that....

Re: Holly HP EFI-- Idle & IAC Tuning
 

Just saw this post. Bradenton-SGMP-Bradenton I haven't had a chance to respond. I agree with the suggestions above.

There are many ways to make them happier but they are a little more complicated.

One things is be sure that the injector data is correct. Voltage Offsets if wrong can make the injectors inconsistent in their operation.

Another is to look at your target idle speed. Be sure that the TPS reading returns to 0 or 1 at the idle setting. If using Idlespark it needs to be within 200 RPM of the target to work well.
Idlespark with chase the idle speed with timing up or down 8 degrees.

If it doesn't start well your cranking fuel or timing might need some work. Also after start enrichment for the first 100 seconds or so after startup.

If using the closed loop function on a stocker with no exhaust you need to turn it off util a higher flow through the collector. Anywhere from 4000 to 6000 RPM. Below that you will need to massage the fuel table to make it happy in open loop.

That's a good start of several things to look at.

Robin

Re: Holly HP EFI-- Idle & IAC Tuning
 

Hey Robin is there any issue with using the primary pipe on header for O2 to ecm tuning during a run?

Re: Holly HP EFI-- Idle & IAC Tuning
 

Not really any issue. Chevrolet Performance did just that during testing on the COPO's in 2013 and 2014. I believe they had worked on the cylinder to cylinder on the dyno so it was fairly well matched.

Using the Holley to perform closed loop in the primary allows you to enable closed loop at a lower RPM. The optimum A/F ratio will probably be slightly richer than in the collector. Optimum A/F is relative so it will need to be tested to determine the best for a particular combination.

Robin

Re: Holly HP EFI-- Idle & IAC Tuning
 

Thank You for that Robin.
Been saying the same years.
People have asked me what AFR I run. Usually turn the conversation to asking where their O2 sensor is located and why optimum AFR may be different due to location if simultaneously recorded. Then go on to explain how fresh air is sucked into the collector. At low RPM fresh air influences the sensor even when located in the primary tube.
Not always easy to wrap your head around this stuff but once understood opens a lot of doors of understanding.

Re: Holly HP EFI-- Idle & IAC Tuning
 

Use open loop at idle then go to closed loop after 2000 rpm