Allpar Forums banner

Random Misfire

1980 0
I have a 2005 Magnum RT 5.7 liter hemi, 83,000 miles. I am getting a random misfire code (I think its code 300 or 330) almost every day. This only happens on first start of the day, when the engine is cold. For the first 30 seconds it will run rough. When I get it above 35 mph the roughness stops until the next cold start. Warm starts are no problem. All other times car runs OK. Only cold starts have the random misfire. Replaced all plugs at 81,000 miles when this problem started, no help. Recently pumped injector cleaner through the fuel rail for 15 minutes. Worked OK for 2 days, then roughness came back, again only at cold start. No code for individual cylinder like 300-3 or 300-7. So it is not assigned to one specific cylinder. Any clues as to what will solve this problem?