I have a '03 Ram 5.7 Hemi with 200k that I have kept up on maintenance and replaced parts with primarily Mopar parts when needed. Only issues that I have noticed is a little puff of light colored smoke after the truck has been at idle for a long time at operating temp but only puffs once and that it. I also have never had really good gas milage (12-14) however my foot is heavy and I don't do a ton of highway driving so I figured that was pretty normal.

Today I left the house without letting the engine warm up (about 40 degrees outside) and immediately had issues with the truck running poorly, misfiring and running rough.
When I got home I cleaned the throttle body (which was super clean) and checked the codes....

P0300 (random/multiple misfire)
P0301 (Cyl 1 misfire)
P0356 (Ignition coil F (#6 I assume) circuit malfunction)


There have been no issues leading up to this event and it ran fine yesterday. So I have a few questions on direction.....
How are the cylinders numbered? How do I know which is #6 ?
I do probably need to replace the plugs as it has been a while since they have been changed but should I replace the coils also?
I am unsure what would cause this to happen suddenly and out of the blue so does anyone have any suggestions other than the plugs or wires that might fail without any other symptoms with these codes?
I did read a little about valve springs breaking in these trucks, so could it be that?

 

Update
I replaced all the plugs and cleaned the PCV valve, IAT sensor and MAP sensor. I also unplugged the upstream O2 sensor as well.
And still misfiring like crazy.

Also, I figured out the cylinder firing order so Im good on that.

I am going to switch the coil packs around and see if that makes any difference.

 

Step 1: Electrical power source. The computers do a kinds of weird funky shenanigans when the power gets flaky. What is the age and condition of the battery? Fully charge it then load test it then replace it with a good quality if necessary. Check terminal connections for cleaning of corrosion, tightness, full contact. Check the alternator function.

Multiple codes all of a sudden like you describe, is nearly always power source related. There is probably nothing at all wrong with your engine or sensors.

 

FaceDeAce.....
I believe the battery and alternator to be good as it shows 12.3-12.5 volts all the time and when running it is at 14.3-14.4 volts. There is no corrosion on the battery and it is a good quality battery that was replaced about 2 years ago.
So I cleared the codes and I am only getting a P0300 code at this point and it is still running like crap and won't idle at all with out me giving it throttle.

 

So switching the coils around didn't seem to help either however in do that and testing them I did find a dead coil (#6) which was replaced. However it still is missing and hesitating especially under load like accelerating.
So I'm leaning toward a broken valve spring...just a guess at this point

 

One broken valve spring won't give you a random cylinder misfire. If you have one bad coil, I would be tempted to replace the rest of them as well. They all live in the same environment.

 

So the codes on the truck after wiping it and changing the coil are now....

P0202 - Injector #2. (However I had good pressure from the tube with a pressure gauge test)
P0351 - Ignition coil #1 primary circuit. (this is the coil I just replaced)
P2299 - Brake pedal position/accelerator Position incompatible. (im sure from the way I had to drive it with 2 feet and in and out of neutral to keep it running)

HeyYou.....I am working on getting a set however no one in my local area carries any more than just 1 coil so I have to order them. I also no longer have the multi misfire code so I guess I am going to check the injectors. and have a compression test done.

Any other thoughts from the crowd???

 

Before ordering parts, or while waiting for parts you could try moving the suspect part(s) and see if the fault code follows it.
Examples:
- move injector #2 over to #4. See if the new code afterwards shows #4 or ?
- move coil #1 to #5. See if the code for coil moves to #5 or ?
Intent is to verify the problem is the specific part by moving that suspect part and verification is if the code follows the part. If so, replacing the part will fix your problem. If not, then there is some other phantom yet to be exorcised.

I am fortunate to have not yet had to deal with any coil problems, (yet). The hemi has 16 plugs, two plugs per cylinder. One plug is combustion ignition the other plug is waste exhaust. They do not go off at the same time. The combustion plug is paired with the exhaust plug on a separate cylinder. I am not absolutely certain of the pairings and someone could hopefully confirm. They may be 1+6, 8+5, 4+7, 3+2. Point of saying this is that a coil code for #1 may actually be rooted in the the paired waste coil or spark lead from #6. You may not be dealing with a coil problem on #1 but actually an ignition wiring problem coming across from #6 ... maybe. Or maybe a crossover wire is hooked up to the wrong cylinder.

... picture for reference. Grabbed off the web.

Hope that helps.

 

FaceDeAce.... What you said is now my exact plan of attack!! The injectors will be my next hurdle to see if I can isolate the injector that is the culprit! The coil code I believe was from before when I was moving the dead coil around. And thank you!!

 

UPDATE.....

So after a long couple of days and time wasted I have a dead #1 cylinder so I am off to pull the valve cover off and hope that it is only a valve spring!!!!!

So a couple of questions for the forum if in fact it is just a spring.....
1. Is it worth replacing just the broken springs? Or should I replace all the exhaust springs? Or replace all the intake and exhaust springs?
2. I have read on here that you can replace the valve springs with the 6.1 springs. Is there any modification to do that?
3. I also saw in the forums that people have had good success with a special Hemi tool. What one is the easiest or best one to use? And where do I order it from?
4. Is there anything else that I should get or keep a good eye on while doing this?
5. Do the early 5.7L Hemi's have the rocker arm bearing problems that I have seen with the others?

Thanks in advance!!!!