Having a problem with my stock 99 dodge dakota V6. The problem is when I first start the truck up it will sometimes idle at 500-600 RPMs and other times it lands in the 1300-1500 range. Sometimes I will start it up and it will run at 500 RPMs and while Im driving (not changing any accessories on or off) it will start to just drive itself. I.E. mantain 40 MPH. When I pull it out of gear it will spike to 2000 RPMs and hold there for a min or two then sometimes drop. I know that is confusing but I have cycled everything off and on and cant pin point the problem.

What I have done:
-Replaced IAC motor and cleaned plunger
-Replaced TPS
-Reset computer
-Checked for air in coolant
-Ran computer (No current or Stored Codes)
-Checked all levels and cant see an obvious leak.

Confused as can be.

 

First thing that comes to mind for me would be vac lines. I know it sounds obvious, but have you really taken a look at every single tube you can get your eager beaver eys on?

**Edit**

I should add what to look for on these tubes. I assumed by what you have already done that you would know, but just in case (and also for any newcomers who look at the thread in the future)... You are concerned with checking for cracks or signs of deterioration. A vac line could also be clogged or just partially clogged and that would screw with your idle like you are talking about. If you're not sure which ones are the vac lines, focus on all tubes and figure out if it is a fluid or an air (vac is referring to air suction differences) carrying tube (by either tracing it or by squeezing it). If that doesn't help narrow it down, you can also just start with the throttle body and work your way away from there.

Hope this helps you and any bushy tailed noobs like Past-Rantz. Past-Rantz used to flounder a lot with these sort of things, but then he learned and became Present-Rantz- that'd be me lol

 

Vacuum lines? Wha? Dakota's dont have a problem with vacuum lines...

(In laymens, I agree with Rantz)

 

That Smiley is dark... just dark lol

Is it not only dripping, but bleeding sarcasm? Oh my

 

I will look at the lines, but from first inspection all of the lines look fairly new and in pretty good shape. I have no idea what it could be.

 

I completely forgot about the trick with carburetor cleaner. KillerKilgore reminded me of it in another thread. You can spray carb cleaner on these vac lines and if there is a change in the idle of your truck when you do, that indicates a leak in that area where you sprayed. This won't reveal clogs or partial clogs, but it will reveal leaks (which would indicate old damaged hose). So props to KillerKilgore for this because I suck and completely forgot.

**Edit** Carb cleaner is flammable so don't go spraying it on the hot exhaust pipes carelessly. Don't stress either, just be mindful of your spray stream.

 

Spent an hour this morning looking for a leak and or a clog. None found... as a matter of fact they look just fine. Any other ideas?

 

The MAF sensor on your intake just before the throttle body may be dirty and/or malfunctioning.

 

Checked it and there doesn't seem to be a problem. Now just messing around I unplugged my computer... All three plugs... waited a few and plugged them back in. Seemed to have fixed the problem, but every time I restart the computer it does this for a day and goes back to running like crap. Possibly a bad computer???

 

any codes? mine had a p601 and i needed a new pcm