Hi,

I have three 2nd gen rams, two 2001 2500s and a 1999 1500 that is my current work truck. The two 2500s were bought cheap as each one has issues.

I am getting ready to swap out transmission between the two to make one to replace the 1500. This is a 2001 long box 2500 and it has a bad tranny but the engine seems fine. When starting it, it runs ok for a short bit then it begins to idle roughly, the engine seems to winding down but doesn't die. It does this for about five minutes before it settles down and idles evenly.

Any idea what this is? I thought maybe a cold start valve but it seems too warm out still for this to be an issue.

I'm concerned that I'm about to do a transmission swap on to a truck that has more serious issues than I thought. Input is appreciated.

 

There is no cold start valve. Might be the Coolant temp sensor being flaky, or even IAT sensor. Check the plenum as well. (see stickied thread at top of this forum.)

Got rear disk on those 2500's? Interested in selling some parts? Where ya at??

 

Pre-cat oxygen sensor is my best (and usual) guess for this symptom. The quick check: Unplug the sensor and see if the symptom disappears (might throw a code/light the CEL, though). Or, less certain but still telling: When it begins to stumble, rev the engine to about 1500RPM for 15-30 seconds to get more hot exhaust gas flowing over the sensor to warm it, and see if the idle is improved when you close the throttle afterward.

 

Sounds like iac, mine did the same