I have an 03 dodge ram 1500 with the 5.7l hemi, out of nowhere it got a bad misfire, idles very rough at 300-400 rpm and eventually dies. while idling rough if you sit inside you can watch the lights dim, I load tested the battery and it passed. same with the alternator, I put my volt meter on the batter and it charges at 12.7-13.7 so its charging but a low charge. I also unscrewed the upstream o2 sensor to see if the cat was plugged and it didn't change anything. also removed air filter, didn't change anything. im at a loss and this is my only vehicle. can someone help me? im new here so it might be a little hard to remember how to get to this. so either reply on here or you can shoot me a txt message. 928-301-5096

 

Check for any codes, a bad misfire should set at least one. That should tell you which cylinder is giving you problems. Think I would find out what is really going on there before driving it much more...... may have dropped a valve seat, and that can destroy an engine pretty quick.

 

Maybe a vacuum leak?

 

ive had the battery tested and the alternator tested. when I put my voltmeter on the battery its charging at 12.7-13.7 volts with the extremely low idle. pulled the upstream o2 sensor so see if cat was plugged but it didn't change anything. just got gas earlier that day so I put a treatment in the tank to get rid of any water and put premium gas in as well but nothing changed. just grabbed my fuel pressure tester, gonna see what the pressure is reading. could the alternator be whats causing all of these problems. of it took 2 days but it finally threw a code, random multiple misfire. also every now and then its starting to pop like back firing in the intake?