Mechanics

SPUTTERING AT STOP OR LOW IDLE

2002 Dodge Dakota

Engine Performance problem
2002 Dodge Dakota 6 cyl Four Wheel Drive Automatic 108000 miles

Thd truck will sptter and cough at a low idle or a stop. Pressing the pedal to the floor will result in the idel smoothing out and the truck continues on without a hitch. No problem at highway speeds at all. The following have been changed: plugs, wires, coil, Throttle postitions, O2 sensor, IAC, MAP, and Fuel Pump. The only codes we have goten are small and large EVAP system leaks and an oxygen sensor. I am at a loss. Thinking maybe PCM? Or the natural vacuum leak detection switch. Any help will be appreciated.
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Dungy74
July 22, 2009.



Ok if you would get me the code numbers the P? Codes. If you don't have a code reader then call around to your local parts stores and see if one will do a free scan and have it scanned. Write the codes down and then have them cleared. Get back to me with the pressent codes and I will look them up and see what should be checked out. Thanks.

Racefan966
Jul 22, 2009.
The codes given today were: P0031 and P0138. I just noticed all of the typos on my original post. Sorry about that. And thanks for the help.

Tiny
Dungy74
Jul 22, 2009.
Ok P0031 is 1/1 O2 sensor circuit low. P0138 is 1/2 O2 sensor shorted to voltage. So I need to know if you have a digital multi meter and if you are willing to do some testing to see what is going on? Do you have a code reader handy? Get back to me so we can run some tests. We will tackle this one code at a time ok.

Racefan966
Jul 23, 2009.
I do have a digital meter. Testing is no problem. I have already replaced the upstream O2 sensore but not the down stream.

Tiny
Dungy74
Jul 23, 2009.
I forgot to mention that the sputtering and coughing will cause it to stall occasionally. If I restart it after a stall or shut the engine off when it is sputtering, it will often restart and run without any issues. Almost like it resets.

Tiny
Dungy74
Jul 23, 2009.
OK lets check the auto shut down relay. What I need you to do is remove it (with key off) and check ohms between term 85 and 86 it should be 70 to 80 ohms if not then replace it. The relay is in the underhood fuse relay box. Let me know how it goes.

Racefan966
Jul 24, 2009.
I did not see anything labeled the auto shut down relay. I checked the Chilton book as well. I checked the engine relay, thinking it might be the correct one. It is at 76 each time I check. Was that the correct relay?

Tiny
Dungy74
Jul 25, 2009.
It should have been next to the fuel pump relay.

Racefan966
Jul 28, 2009.
The relay next to the fuel pump relay is labeled " Spare" I just double checked. 202 Dodge Dakota 6 cyl

Tiny
Dungy74
Jul 28, 2009.
Ok lets do an O2 sensor test. I would like you to do this with all the O2 sensors even the new ones ok. Now I have included a pic too. What you need to do is unplug the O2 sensor that you are testing and then ohm the sensor between term 2 and 3 or 2 and ground. Ohms should read 3.3 to 4.1 on the upstreams and 4.0 to 5.0 on the down stream ones. If they do not read this then replace the ones that don't. If this is good then you will need to check that they are getting voltage form the auto shutdown relay. This is done by again unpluging them and checking term 1 on the wire harness not the sensor and then turn the key on engine off it should read 10 volts or more. Let me know what you find here and we will take it from there. Don't forget to plug the sensors back in after the tests are done. I would turn the key off between test on the sensor as to not drain the batt. Get back to me with what you find.

Racefan966
Jul 29, 2009.