HI!, I have a 2003 Ram 1500 5.7 throwing aq P0302 code with engine running rough and 240,000 miles. I checked Spark Plugs and they look fine but and smell like Fuel so I'm thinking Coil is possibly bad. Is there a way to check the coil with a muti-meter or without switching it with another and seeing if the code follows. Truck starts right up, idles but with a lope like it's gotta HP Cam. Does run rough but seems to smooth out some when warm and higher RPM. If i put a timing light on the the wire going to #3 cyl . would that indicate bad coil?

 

Swapping 1 and 3 coils shouldn't be too much of a chore. Then see if the miss moves with the coil.

 

P0302 is misfire on #2 cylinder.
Timing light on the #2 wire (you stated #3 but assume you meant #2). This would be part of troubleshooting to gain info on the problem. I would decide in advance what it means if I get a timing light signal, and, if I don't. If you do get a light, then problem is down to coil, boot, plug, rings/piston, fuel management, or O2 sensor.
I'd rec you go with swapping the coils.
If problems goes with coil then replacing the coil is next step. If problem stays with #2 even with new coil, then I would get a live data OBD2 reader and make sure O2 sensors are operating properly. There will likely be other opinions on what to do if problem stays with the cylinder, just letting you know what I would do because I've often seen faulty O2 sensors cause misfires.

 

Spark plugs DO go bad.
They can crack and loose the ability to transmit that spark to the end of the electrode.
As suggested, swapping between the #1 + #2 coils is real easy, but I'd pull the plug and take a look at it as well.
Maybe put a Ohm meter on it if you don't see any visual clue's that it's bad.

 

I did look at the plugs on the #2 Cyl. They looked good but were wet and smelled like fuel. I an going to switch coils today and see if the code follows. Just for ****s and giggles i'm going to put a timing light on the wire coming off the #2 coil and going #3 cyl. and see if it flashes.

 

Just to add.
2003 5.7 is known for broken valve springs.

 

Big Guy, That thought has crossed my mind. I had a 73' 340 that I rebuilt the bottom end but not the heads some almost 30 years ago during break in all of a sudden it had a hard time starting but when it did start would run fine until about 2800 RPM then srta bucking and backfiring. Checked compression - fine, Spark-fine, Timing-Fine. So took head off, checked lifters and pushrods- seemed fine. stood there baffled with my hand on the head sitting on the bench and realized all the retaining capps on springs did not move except one on the exhaust side of #8 Cylinder! Inspecting it closely with flashlight AHA! inner spring was broken! Not one to do things TOTALLY half A**ed I replace all the valve spring, oil seals (they came with the gasket kit already so why not), reassembled and turned it over a couple times and took off ! She still runs great 28 years later in my 73 Dart Sport. Sorry to run on but i was happy as hell seeing I'm a shadetree mechanic on my 2nd rebuild. Anyway this 5.7 starts right up ides fine and only shudders and shakes at highway speed in OD. I guess I'll find out more today when I put Timing light on wire going to secondary #3 spark plug.or switch coil location and see if code follows.