Diagnosing Dodge Dakota idle stuff

To be fair, I did a ton of googles about this, but before I sign up as a noob on the 35 common "mydakotahasstickers.forum" websites - I thought I'd ask you fine folks. (cuz I know there are a few Dakota owners here)

My 02 Dakota 3.9L has an idle issue. If I stab the throttle and let off, it dies. If I'm in traffic and give it some throttle then back off, it dies. I've googled and found a few hundred things about IAC and dirty throttle bodies. The IAC problem (according to the internets) always shows up first as a CEL. I pulled out my IAC and it looks squeaky clean but I can't test its operation. I pulled the TB off, removed all sensors, and cleaned every orifice. That didn't change it.

Normally I wouldn't care for myself. I own lots of vehicles with deadly quirks, but I'm thinking of selling it and I am not the type of person who BS's or masks things. I want to fix this before I sell it so I'm not passing the buck.

Do I randomly throw parts at it? IAC? Spark plugs? The truck only has 85k on it.

I'd probably throw an IAC at it first since they are about $20 on rockauto.

Belly pan gasket.

Take the TB back off and look down into the intake for a film of oil on the bottom.

The IAC's didn't always trip the CEL. Change it and see.

Also check the Temp sensor and the MAP.

Also one odd issue with some of these era Dakota's is that the ground paths get corroded and screw up all the sensor information to the ECU.

Not necessarily a Dakota specific issue, but what about the torque converter going bad and inducing too much drag? Any transmission leaks?

Good luck.

I have a similar issue with my 4.7. It's like a vacuum leak that constantly comes and goes. Push in the clutch, it picks up RPMs or RPMs hang . . . Come to stop, it either picks up RPMs or RPMs hang or tries to stall out.If the RPMs hang it will settle backto idle after 20 or so seconds.

TPS and IAC are new . . . TB cleaned. Checked all the wiring and connections. Did the ECU relearn. All of the hoses have been checked and vacuum caps replaced. Plugs going in today. After that, the only thing left is intake gaskets

Does Chrysler still adjust idle based on vehicle speed? On the older Chrysler's inability to idle when coming to a stop indicates a vehicle speed sensor issue.

Yah, I was going to suggest throttle body. Pretty common. But if you've already checked that... the map sensor is a piece of crap too, it's pretty easy to change. I think the belly pan problem just caused nasty pinging though, not idle issues. There used to be an aluminum replacement pan you could get (the stock ones are steel and expand at different rates than the aluminum intake).

Do you have a scan tool that will let you see the data stream? I'd lean toward IAC as well. See if you can find a Standard AC68. They are a little more money, but a little better quality. Don't go for the AC68T. That's the budget one to compete with the AutoZone/Advance house brands.

Lesley wrote: Yah, I was going to suggest throttle body. Pretty common. But if you've already checked that... the map sensor is a piece of crap too, it's pretty easy to change. I think the belly pan problem just caused nasty pinging though, not idle issues. There used to be an aluminum replacement pan you could get (the stock ones are steel and expand at different rates than the aluminum intake).

Hughes Engines makes them. Nice piece, but buying one isn't Curtis' style. He's more of a hunk of 1/4" aluminum plate, replacement gasket, sharpie, jig/band saw kinda guy.

And yea the issue is usually pinging, oil consumption, higher idle/mystery vacuum leak. Been there done that.

I changed it out for an M1 2bbl - one piece, no issue. The idle/stall problem was so prevalent when I had my 3.9L, that I kept a box of j-cloths and tolulene (throttle body cleaner) in the truck, to wipe the carbon out. And every couple of months, I'd take it off and clean it thoroughly.

My 97 Dakota does this. It also tripped the CEL for the IAC, so I pulled it, hit it with carb clean, cleaned out the throttle body, reset the ECU, and it was good for a while. My truck sits a lot, so I have to do this from time to time. It's part of the fun of owning a Dodge Dakota with the 3.9L V6. It is very annoying.

It is, but that motor is virtually indestructible.

Update. Tried a new IAC, same issue. So I cleaned the old IAC, same issue. Pulled the entire throttle body, took all the sensors off, and cleaned every last molecule of gum off of it. Same issue. Still no CEL. Put it on a scanner, everything seems to be reporting properly. I used jumper cables to ground the block to the negative battery terminal, same thing. Pulled the plugs again, look brand new.

Anybody want a CHEAP DODGE DAKOTA?

Just a stab in the dark here, but what shape is the battery and charging system in? I had a turbo Spirit that did some stuff along the lines of what you are describing when the battery was weak.

This is the Dak that was in the accident, right? And I'm guessing it followed you to Carlisle.

How are the battery connections? Mine died 100 miles from home at a gas station one time, pushed it across the street to the Chrysler dealer (handy huh?) where they replaced the cables.

Try a vacuum gauge.

Rob_Mopar wrote: Just a stab in the dark here, but what shape is the battery and charging system in? I had a turbo Spirit that did some stuff along the lines of what you are describing when the battery was weak. This is the Dak that was in the accident, right? And I'm guessing it followed you to Carlisle.

Yes, accident Dakota. Battery new as of this past August, but it did this idle thing before with the old battery too. 0.01 ohms between multiple points of the engine and the neg terminal, and voltage at the battery is 14.56v running at 1800 rpms, 14.37v at idle with lights on.

I'm really tempted to get another ECM and try it. There is no chip in the key so maybe no reflashing required? He asks hopefully?

I can send you a 3.9 PCM, but it would only work for testing purposes. It will run your engine, tranny will shift properly... but the gauges won't work.

Lesley... thank you but... VICTORY IS MINE.

The little J-shaped hose that goes from the TB to the MAP sensor had a pinhole in it. Replaced it with a snip-off from a bucket full of spare hose and problem GONE.

Ahhhh. I feel like I just took a big satisfying dump.

In reply to curtis73:

Congrats on the victory. And your eloquence never ceases to amaze.

That's awesome. I hate the frustration of trying to diagnose mystery problems.

Rob... if you thought that was eloquent, you should have seen the actual sh... nevermind.

Lesley, thank you for digging and finding that ECM even though I didn't need it.

I replaced my dakota with a 4runner and fixed all my problems

Haha... I'm fixin' to replace my dakota with ANYTHING. Maybe even replace it with an empty spot in the driveway.