After figuring out and fixing my random shutoff, fixing some brake lines, and getting my transmission rebuilt again... I noticed my truck has an oddly high idle in park. Before said work, it used to reliably idle at 700rpm

I've tried a couple of IACs and I don't think there's a vacuum leak (reads 21-22 inHg). Would think the idle relearn would have had been done by now after a week.

1998 Dakota with the 3.9 v6
Cold start: 700rpm.
Warm with a/c: 750-800rpm
Warm in gear: 650-700rpm
Warm in park, no accessories: 1000-1100rpm.

I would figure in park warm would be the lowest idle... It also idles properly before it reaches temp, which I would figure would be opposite, high idle to warm the engine. Neither cruise or vent controls go wonky on low vacuum situations, but I'll check my vac lines again. Is there a proper idle relearn procedure?

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Could try resetting the PCM, then, turn the key on, count to ten, then start it. That lets the PCM relearn the various 'zero' values on the sensors. Will it make a difference? Don't know.

Probably wouldn't hurt to plug in a scanner, and with the engine fully warmed, see what the PCM wants for target idle speed.

 

Planned to drop by my brother's place this weekend, he has a Snap-On Solus Ultra and I'll see what it's thinking. Least it isnt horrible high, like 1500-2000...

 

IAC hang is not abnormal sadly. Should be able to easily learn..as suggested, see what target idle is. Can also sweep the IAC...i know the DRB3 can, Solis should be able to.

 

Any vacuum hiss coming from the motor area... sorry im old school, that doesnt apply anymore does it.

 

Well, finally revisited this issue and well... This happened:

LmLZ9l5.jpg

I think my pushrod engine can handle 16k+ rpm, what do you think? Happened to have a bluetooth OBDII adapter + Torque open when I was watching RPMs to compare them to the tach, shifted into reverse, and that happened. Caught the screenshot before it corrected itself, thought it was funny. Anyway, moving along.

Fixed the issue, thought about it and remembered it started about the last time I had the throttle body off. Popped the hood, thinking maybe when I put the bracket back on that holds the cables, maybe I got it a bit crooked causing tension. Popped the throttle cable off and boop, the throttle butterfly moved a little. Pulled the throttle cable taunt and it was still about 1/16" from reattaching, had to pull the throttle slightly to reattach. So the throttle cable was holding the blades open slightly, so even with the IAC completely closed, it was getting air and adding about 3-5% on the TPS. (Note in the screenshot, TPS is reading 16.5% throttle, I'm used to it reading about 12-13) Popped it back off and looked at the bracket, obviously the previous owner had janked it around a little (I guess when they swapped the engine, still finding stray idiotic things). The plate the cruise/throttle cables attached to was bent out about 105-110 degrees instead of closer to 90. Took a large pair of channel locks and very gently bent the bracket closer to 90 degrees until the throttle cable seated without having to move the butterfly, but without slack. Fired the truck up, 900RPM, after a moment, dropped down to 650-700 where it was supposed to be. Didn't have time to let it come up to temp to see if it'll stay there, but moved it through the gears and back into park and dropped back where it should. I knew it had to be something stupid...