I cleaned the TB and IAC on our '05, 4.7 with MT, and now it doesn't want to decelerate until after I shift to neutral. Drive at say 80 KMH (50 MPH) take foot off gas to slow down and it barely slows. Shift to neutral, RPMs around 17-1800, brake to slow down and watch tach and it will ever so slowly go down to 800 RPM.
Does PCM memory come into play here? When truck is parked I usually disconnect battery as it might not get used for weeks or months and otherwise the battery will go dead.
It never did this before I cleaned the TB and IAC, but what it did do was after a highway run it wanted to die instead of idling. Ferinstance, take an exit ramp, come up to a stop light and it would die unless I shifted to neutral and worked the gas pedal to keep it running and after a bit it would be OK.
I suspected the IAC was sticking so that's why I cleaned it and the TB.

 

your iac is on its way out, may have to replace it, also when you reinserted it into the tb, did you rotate it back into place?

 

Time for a new IAC.

 

It only goes one way, methinks you're thinking of the TPS? Or am I missing something here?

Got a new IAC on order, in the meantime I'm thinking of disconnecting it and adjusting the idle w/the throttle plate adjusting screw.
Ifn I disconnect it will it throw a code?

 

With the IAC, you need to make sure you don't pull the shaft out any amount - this can (and often does when people pull them apart partially to clean) damage the unit. They aren't repairable.

 

Update: Well that's 80 bucks down the drain, put in a new IAC and it still doesn't want to decelerate when taking the foot off the gas pedal. Go 80 or 100 kmph or whatever and it doesn't want to slow down, shift into neutral use the brakes to slow down and see the rpm at 1500 or 1800 for a while before it drops to an idle.

Here's the plan, I'm gonna check the resistance of the old IAC, find a resistor to mimic it, disconnect the IAC, connect the resistor in it's place, set the idle w/the "do not adjust" screw on the TB and go from there.

Any thoughts on this?

 

It kinda sounds like you may have a vacuum leak. I would check that, since it only takes a few minutes and doesn't cost anything.

 

I'll check that but methinks if it's a vacuum leak it would act up more than just when decelerating.

 

Checked for vacuum leaks, couldn't find anything.
So instead of using a resistor I just unplugged the IAC, plugged the old one in and left it laying on the manifold. Adjusted the idle up and it works great. Now the truck decelerates when I take my foot of the go fast pedal.

 

After chasing this "doesn't want to slow down" problem for about three years I've finally resolved it. After replacing both the IAC and the TPS twice, once w/aftermarket and again w/Mopar parts, checked for vacum leaks, checked emissions system, had it into 2 different reputable shops that both said they could fix it and later said there was nothing wrong w/it, I figured it must be in programming, so I ordered a replacement ECM, installed it and problem is finally gone.