I have a 2003 Ram 1500 with the 4.7 L that has a rough idle at a stop light or sign. Sometimes it idles bad enough that it dies but it will restart. It doesn't set any DTC's. I have tried a new throttle position sensor and downstream O2 sensor. If i unplug the downstream O2 sensor the truck seems to run fine. Any one have any ideas? Any help will be appreciated

 

By downstream, you are referring to the sensor after the catalytic converter, correct? Just making sure, some people confuse the downstream/upstream definitions.

For future reference:
https://dodgeforum.com/forum/dodge-r...s-section.html

 

When was it's last tune up. throttle body cleaning.

 

Yes i am referring to the one after the converter. As far as the tune up i don't know. My friend has owned it since May and they haven't done anything to it. i did check the throttle blade. I didnt see any build up on it. And i did remove the IAC and check it. There wasnt really build up on it either. I did use a rag and wipe it clean.

 

I had a misfire in one of my cylinders. One of my plugs was smashed and had the incorrect gap. It ran rough, and I would pull up to a stop light and the truck would just shake so bad. My truck didnt throw any codes for a day or two. Might pull the plugs and check the gaps and see if they need replaced.

 

Start with a tune up. Unless the previous owner knows when it was done.