I'm thinking the IAC valve I got is bad... Possibility? Anyway to check?

 

That has happened. Was it a mopar brand? Our trucks prefer them. Without looking at a svhematic, I know you can apply 12v to two of the contacts and watch extend (or contract, my memory fails me right now). That is about the only test but I would replace it just for grins.

And clean the seat for the IAC inside the throttle body.

 

1996 ram 1500 5.2l 4x4 having the same problem once in a blue moon it idols correctly but 99% of the time it idols high but settles then in park or neutral it shoots up to 1400-2000 rpms. I have smoke tested the intake and no leeks I’m also running the mopar intake so there is no plenum leak on the bottom because it’s solid. I have replaced every sensor on the TB x3 I have cleaned the throttle body I have replaced the throttle cable, I have replaced all the o2 sensors. I have reset the ECM so many times I can’t count. And high idol is still there lol any thoughts.

 

I had this too but while driving ut was the brake switch that connects to the pedal it was going out making the truck think I was tapping the peak while driving sending the torque converter in/out of lockup 12$ prob min my case maybe the same for you

 

Purge valve stuck open? Brake booster got a hole in it?

Have a scanner that can read live data? If so, let the engine fully warm up, and see what the PCM thinks Target Idle should be.

 

just did a full brake job and put in a reman booster (duralast) still idols high in park and neutral. I work at a shop and have had the techs hookup 2x to my comp but for some reason they can’t scan it or only partial scan and they couldn’t find anything. No one has ever told me purge valve and idk what that is let me do some googling lol.

 

Ok I have seen the purge valve and have taken it off before when doing work on the truck but never replaced it I will replace it Thursday when business open again and report back thank you for the suggestion.

 

Check out your vac lines and pcv valve. Both can leak and cause a high idle.

 

Checked the plenum gasket? An external test for that doesn't exist. (aside from actually looking in there....)

 

I have done a smoke test no vacuum leaks.
I have a mopar intake not the “oem barrel” their is no gasket under my intake it’s solid metal. I did Heads and cam about 4months ago and I’m confident the intake is not leaking + if it was smoke test would show correct?