Using Two IAC valves

[Slow94]

Tried to experiment with using 2 IAC valves on my lightning by splitting the signal. What happens is neither will run if both are plugged in and you have to unplug one in order for the other to work. Is there possibly a simple explanation to why this may not be working? I'm assuming with both plugged in they aren't getting a proper enough signal or they are causing interference with each other. Anyone have any suggestions that could get it to work? Maybe add some diodes or something?

[decipha]

i doubt it has enough current to sink 2 iac's, careful could burn up the output

best bet would be to have the second iac go to a relay that gets its trigger from an unused output.

would be simple enough to write code for it just need a few conditions

Code: Select all

if on goto disable  //otherwise check enable criteria below

:enable
if desmaf > 1.9
if ect < 120
if rpm < 2000
enable iac relay
bypass air += xx  // this is to subtract the amount of airflow the valve provides so you can still dial in idle air

disable:
if act > 90 **backup if ect fails**
  -or- if rpm > dsdrpm+300  &&  dashpot ==0 && cttmr > 6
disable iac relay
bypass air -=xx

should be simple and do the trick

maybe use the fuel cap lamp output, unused anyway may not exist though. High speed fuel pump output would need some finesse to make do.

[Slow94]

Interesting. It's really only under very specific circumstances that I need the extra airflow. Once I get past those circumstances once it's no longer an issue as the truck continues to run. The first shift into gear with cold trans oil temps make for a huge load change and will shut the truck off. My truck has a very aggressive trans so it is violent. I can just blip the throttle some with that first shift into gear and she is fine and I can then go back and forth just fine. I may be just nitpicking.

[decipha]

that usually means the seal on the trans filter isnt secured or is leaking, has nothing to do with idle air

i take it you have a bigger pan, did you use the bigger filter for the larger pans? do you have a filter retainer?

[Slow94]

Nah it ain't that. Since going built trans it has always done that and I just had it out and upgraded. It just has a lot of pressure mechanically I suppose. If I have regular street tires on it will chirp tires going in gear when cold lol. I have tried taking as much pressure out as possible but it doesn't help. Couple of the other built trucks deal with a similar issue sometimes. It's only the very first engagement generally and then after that it's usually fine and of course goes away when it warms up. I have everything working against me really. Built motor with less vacuum, built trans that hits like a brick, and a custom blower set up that requires a remote IAC so flow through it probably isn't as good as stock even. I run a lot of throttle blade to help. When fully hot my IAC is basically doing nothing and I'm completely holding idle speed with timing control only so I have full range of my IAC valve... While this definitely helps it still isn't enough. I know that just a bit more airflow will solve it because like I said if I just crack the throttle just a bit it won't die when I encounter that situation. I have thought about trying a different valve.. perhaps one from a 2000-2003 v10 excursion.

[decipha]

does reverse bang harder than drive?

what if you put it in 2nd or 3rd gear instead of 1st for the initial first engagement does that change it any ?

if your foot off the brake when you engage it, does it still die?

[Slow94]

Usually in all the built trucks reverse hits harder than drive except for my truck it seems. Mine hits harder in drive "seemingly". I will have to try putting it in 2nd gear first then Drive to see if that helps. And I haven't tried putting in gear without foot on brake as I'm usually in my garage and if I did that it would go through the door with how much force it has lol. I will test that as soon as I can though. I actually just finished up replacing power steering pump just now and I cranked it up and let it run a bit. Was 145 degrees when I put in reverse and it didn't shut off. Trans oil temperature was a bit higher than it has been though as it's warmer out today. The issue is very much trans temp related in relation to how warmed up and stable the engine is as well. That first hit it's like there is extra pressure built up that is magnified when it's cold thanks to the thicker oil viscosity and the truck doesn't have enough airflow to catch it in time. I do know one of the other local trucks his truck likes to do it in reverse and if he puts it in drive first he no longer has issues going into reverse. Again these aren't an everyday problem but it is one of those things that irritates you.

[Slow94]

So putting it in gear without holding the truck with the brake does help. I believe it takes some of the that shock load off and it can catch itself better. Putting in 2nd gear does do better as well seemingly. Now once truck goes in and out of gear a few times it's good from then on

[decipha]

What your experiencing is additional first time engagement pressure henry put in the code for the stock trans. Its set to 45 psi. A built trans on a stocker could damn near throw a rod.

Post your current tune in your thread and we can drop it to see if it fixes it. Should be all it needs.

[Slow94]

What your experiencing is additional first time engagement pressure henry put in the code for the stock trans. Its set to 45 psi. A built trans on a stocker could damn near throw a rod.

Post your current tune in your thread and we can drop it to see if it fixes it. Should be all it needs.

Out of curiosity, is that something we can add into the strategy to tune?