First time poster....

1999 Durango SLT 5.9L. Great truck! But.... My son will start the engine (when cold), drive about 300 yards and the engine will go through about a 2 minute episode where it studders and acts like it want to die but it doesn't. It will eventually work itself out and drive normally. If he immediately throws it in neutral and turns off the engine and restarts right away it will run absolutely normal like nothing happened.

During the troubleshooting process we determined through previous threads that the Plenum gasket was bad. Loss of power, poor MPG, oil view-able in the plenum, etc.
Here's what we've done.
1. Hughes plenum plate/gasket
2. Cap, rotor
3. Platinum Plugs, wires (done last spring
4. Distributor Ignition Pickup sensor after we cut the wire during the plenum install

Power and MPG have returned in a big way with a 4 MPG increase.
Unfortunately, the studder remains. This only happens when the engine is cold. There are a lot of different threads about similar issues but ours seems to be a little different as it seems electrical...

Any help would be appreciated!

 

First, get rid of the platinum plugs, these motors just don't like 'em. Second, replace the front O2 sensor. (NTK or Denso only please, not Bosch.....) Your symptoms describe a failing O2 sensor. (PCM ignores it until it has a chance to warm up, generally, about 2-3 minutes..... if it isn't quite ready yet, when the PCM thinks it should be, you get just that kind of behavior.)

 

Thanks for the info. We replaced the upstream sensor with an NTK this evening. Also replaced the pcv valve just because... He immediately noticed an acceleration improvement when he took it for a test drive. True test won't be until tomorrow morning when he leaves for school.

 

The Durango is running like a champ... No more studder. O2 sensor was the issue. We will replace the plugs as time allows but they seem to be doing ok at the moment. Thanks for the help.

 

Glad ya got it fixed.