So I am Running out of options on Figuring out MY random Misfires and random rough idle Issues. Here's what I have done far. Motor is rebuilt With Forged CP pistons and Sneed4Speed forged Rods, New OEM timing chain and guides and tensioner. ARP head studs, all new valves. New Bosch fuel injectors, OEM Min Valve cover. New OEM High pressure fuel pump. OEM crank sensor, OEM cam sensor. New spark plugs and OEM coils. Replaced fuel filter. Keep getting multiple mis fire codes. Some days no misfire and runs perfect, some days Cold start is fine and smooth and only misfires on hot restart and clears up after 30 seconds, Some days misfire on cold start and runs rough. All that's left to try is map sensors and oxygen senors??? Any thoughts or where to look next?? I do know some of the rough idle is the forged internals but most is caused from the misfires. Motor was rebuilt at 54K and now has 59K. Does not use oil ans no smoke.

 

I wouldn't blame a rough idle on forged internals, otherwise lots of other people would be complaining. Timing is known to slip slightly after initial assembly. It can be checked using the following procedure --- https://www.newtis.info/tisv2/a/en/r...mshaft/4PAbHZs This is for an '07 MCS, use the last seven characters of your VIN for the procedure for your car. Then there's the cam adjuster solenoid --- make sure it has clean screen. Have you checked plug condition --- rich vs lean and all 4 the same? My injectors are all original and have 100K miles --- why were yours changed? Maybe try the originals? Most of my misfires were caused by plugs, either not NGK or wrong temp rating.

Keep us posted when you find a fix.

 

Tried new plugs one step colder NGK 1422. Still misfires. I replaced the injectors as it was suggested that one could be causing the misfire.. timing was checked several times and is right on the money. Ran flawless this morning all the way to work. Restarted after I got to work and misfired upon restart.