Hi all, so I posted along these lines before. 2001 ram with a 408 226/230 cam 110lsa. I have some issues with erratic idling and idle coasting behavior with the 58MM F&B throttle body. I tried a ton of different adjustments with the throttle blades and never got it right. I Just picked up a MT2500 scanner and started over. I've read how to set the IAC a bunch of times from the Bionic Dodge article. Where I am confused is when are you supposed to be reading the counts? At Idle in Park or tuck in gear? Where i am at now is after going in closed loop at Idle I am at 12-15 counts. If I throw the truck in gear, foot on brake Im at 40-44 counts. The other issue is while driving, when coming off throttle to a slow creep the IAC counts go to ZERO and the Idle drops down as far as 550 RPM until I almost stop then the counts go back to 40-44 raising the RPM. Target RPM is 744 according to the scanner Currently where the throttle blades are at the TPS voltage is .59. I don't think I want to go to much lower due to the cam needing some RPM at Idle. Any help would be greatly appreciated.
Thanks again.

 

Have you tried a reset? Basically, disconnect the battery, turn on headlights, turn off headlights, hook battery back up. Turn the ignition to "On", (not start) count to ten. Don't touch anything.... THEN start the engine. This will allow the PCM to learn the 'zero' values for TPS, and IAC. From there, the PCM *should* be able to re-learn idle.

Question becomes, do you have a tune for that 408? With the 110 LSA, you may need to adjust idle up a bit......

 

Agree, the PCM has a target idle that it tries to get to, IIRC it's 680 RPM. 770 RPM is probably already a fault strategy because of poor idle. Can the MT2500 set a (temporary) target engine speed ? If so play around with it to find where the engine is happy. The throttle blade adjustment does only affect the operating range of the IAC, not the idle itself.

 

Thanks. The issue isn’t so much the idle. The truck has been tuned once by performance injection equipment and now I’m revising with Flyin Ryan after changing to bigger injectors and throttle body. The target idle was set when the truck was first tuned. I was having surging issues and hanging idle for a bit after putting on the 58MM. Again I’m trying to ensure the IAC is in the ballpark. Please correct me if I’m wrong but the IAC is supposed to open or close to help maintain target idle. The truck idles fine in park and gear when stopped but the idle drop when coming to a creep and observing the IAC counts at ZERO is what I am concerned about. Is this normal for the IAC counts to zero out? Again am I setting it correctly? Is it set in park or drive? Also I don’t think I can raise the target idle on the MT2500. Thanks again

 

So far as I know, the IAC isn't even adjustable. At all. It is purely PCM controlled.

As for zeroing out, if you are coasting down, having it close off completely isn't unusual. What brand IAC is in there? I had serious issues with an aftermarket unit, that caused all sorts of fun issues, that were ALL solved by putting a real Mopar IAC back in there.

 

So I have a new mopar IAC and TPS. The IAC is the newest revision with the AD letters at the end of the part number updated from AC. Im not trying to adjust the IAC itself but the throttle blades to get the IAC counts correct, Which is why I grabbed a scanner so I can see the actual counts. When the blades were open more the idle would hang and get erratic. So I’m using the TPS voltage now to keep track of where I am with the blades. More voltage is open more and less voltage is closed more. Again the IAC is keeping target idle everywhere but when I slow dow in gear to a creep then it drops to ZERO until I stop which is where I am not sure that I am correct. With the readings I have at idle in park (12-14 counts) this is indicating that the blades need to be closed more which would seem to make the problem worse (idle dropping too low at a creep when the IAC zero’s out). Truck in drive foot on the brake the IAC is in the 40’s so I would have room to open the blades a bit more and get the counts down closer to 30 which is why I am wondering where the counts are read (in park or drive) so I can adjust the blades better. It’s been a crap load of trial and error so far.

 

Both . The PCM moves the IAC to where the engine reaches target idle. Open increases idle, close decreases idle. Note however that the IAC is also used at other times, not only idle. Deceleration is one of them and that appears to be not working in your case. If the IAC goes to zero the air passage is closed so that might be your problem.

I looked at the web site you referred to and it recommends to set the throttle blades so that the IAC is 30-60 steps open. 12-15 is definitely too little and possibly the cause that the IAC bottoms out before reaching the desired number of down steps.

 

Ok so I will assume the IAC counts are read in park not drive. So I am going to try and close the throttle blades a bit more and reset the IAC and see what happens. Only concern is the more I close the blade the lower the tps voltage gets. Bruce from F&B said to try and keep it between .54 and .74. Hopefully it works out. Thanks again

 

There was a similar issue years ago on another forum, I believe the hack was to mod the tps sensor/screws so it could be moved.

 

First off... Talk to Ryan about setting the idle.

Now, with that being said, you're overthinking the process or I'm misunderstanding what you're doing. There is very little you can do about the IAC counts from what I can remember. You need to set the idle first, and the counts should fall in place unless there are other issues.

Setting the idle:
Make sure you have access to the IAC inlet and electric plug.
Turn key on without starting the truck. Make sure IAC is fully closed.
Unplug IAC, this will throw a code.
Now start the engine with your scanner hooked up and out where you can see it.
Adjust the idle screw to set the engine idle at your desired idle... This is where talking with Ryan is really important. He will set the target idle accordingly to your desired idle, and it will probably be slightly lower than you thought.
Once idle has been set with the mechanical screw, shut the engine off.
Plug the IAC back in.
Clear the code caused by the IAC
Turn key on without starting the truck and let it sit for a couple minutes to relearn it's settings.
Shut the key off for a few moments, then start truck like normal.

The IAC is to help bump the idle up if there is something pulling the engine down, it is not there to carry the full load of making the engine idle. That is what the idle screw is for. Hopefully this helps.
Again, talk to Ryan about this. He can fill in any blanks that I've left and correct any misinformation I might have added.