I have a 99 Ram 1500 with a 5.2 that runs very rough at idle and also at speed. When I get on the throttle it smooths out and seems to run fine. It showed a code for the pre-cat o2 sensor so I re-placed that and also changed out the plugs, wires, cap/rotor, and pcv valve. I have ran some injector cleaner through the truck and within the last year I re-placed the fuel pump. The rough running is somewhat able to be controled when I give it good throttle or keep it in a very narrow rpm range when driving. It also showed a code for the injector harness, IIRC, for the number 2 injector. I swapped injectors and it changed nothing. Tomorrow I will try to check the plenum for oil, check for vac issues, and I suppose a fuel pressure test would be in order. Any other ideas would be greatly appreciated. A quick use of the search function gave me some ideas. Great forum. Thanks in advance.
John

 

If you are still getting a code for the number 2 injector circuit, make sure the little clip that hold the connector to the injector is in place, and doing it's job. Clean the connector, to make sure you are getting a good connection at the injector. Pull the PCM connector, and make sure those are clean and tight as well.

What brand O2 sensor did you get?

 

Might be that the IAC valve or the port in the tb is dirty, causing it to run a bit rough. When you get on it a bit, the throttle blades open up more and there is less need for the IAC valve, and it closes up.

just wondering, do you have california emissions truck? More than one precat O2 sensor on those.

 

Thanks for the help guys. I got the o2 sensor at Advance Auto and I forget the brand off hand. No Cali emissions on the truck either. The IAC makes sense to me. I will get to checking that and also the connections that you mentioned tomorrow. I do hear a distinct clicking sound from time to time that sounds like it is coming from the engine bay. IIRC this clicking could be IAC related? I thought I remembered something being mentioned about that when researching with the search function. Cat converter sounds like a bag of nickels when you tap it as well. Thanks again.