Random misfire when engine warm

[RustyNails90]

I have a 05 ram 1500 with a 4.7l. I keep getting a misfire when the engine is just warm. If the engine is at operating temp and I let the truck sit for a little and drive it again it throws a cel for p0300. The temp gauge is right in the middle of hot and cold when this happens. It does not misfire at an idle, only when I put load on it in drive and it only last for about 5 seconds and the truck runs great again. I have already replaced some things in the past like EGR, idle air control, tps, cam and crank position sensors,3 coils. Put fresh plugs in over the weekend and I had another episode today at work. I have tried looking over forums for someone who has had this problem but none of the threads for misfire seem to be the same as my problem, unless I missed it. If anyone has some ideas of what could cause this it would be great!

If you need to know a list of mods I have a k&n intake, Throttle body spacer, and JBA shorty headers, glass pack muffler.

If I remember correctly I heard somewhere it could be the coolant temp sensor but I'm not sure on that.

I'm sorry if this was covered in another thread, I missed it then!

 

[JPT]

From my experience Misfire codes typically are because of a very few things:

1. Bad spark plugs (check gap)
2. Bad Coil Packs
3. Lack of Air (typically would trip the 300 code, not individual as air is common to all cylinders)
4. Bad fuel injectors (I had an o-ring harden on a working injector that let air in causing an intermittent cylinder specific code)
5. Head Gasket/Warped Head - Typically trips two side by side cylinder codes, or more

This is typically the order I try to resolve the issue, because of price/difficulty. Remember number 5 doesn't require removal of head to determine. While changing the spark plugs you can do a compression test (this would be for warped head or bad head gasket) and leak down test (this would be for bad valves).

I hope this helps.

 

[ayesijuan]

Buy good platinum spark plugs (NGK). after chasing this problem for over a year and $800+ I found out that my mechanic put in cheap ass Champions. They worked okay until it warmed up and then started coughing and puking especially when you got on the gas.

 

[Karlsweg]

I would check for leaky intake and valve gear .

 

[Fast69Mopar]

Buy good platinum spark plugs (NGK). after chasing this problem for over a year and $800+ I found out that my mechanic put in cheap ass Champions. They worked okay until it warmed up and then started coughing and puking especially when you got on the gas.

I have to disagree just a little bit. Not all engines react the same way to the addition of a platinum plug. I have had too many customers come in with 3.7/4.7/5.7's with platinum plugs installed because that's what the local parts store said would work best.

In addition, one engine may run okay with a platinum plug while the next one will have random misfires and or a loss of engine performance and fuel economy.

The only 4.7 to come with a platinum spark plug came in the WJ Grand Cherokees with the 4.7 H.O.

 

[B17E1943]

I have to disagree just a little bit. Not all engines react the same way to the addition of a platinum plug. I have had too many customers come in with 3.7/4.7/5.7's with platinum plugs installed because that's what the local parts store said would work best.

In addition, one engine may run okay with a platinum plug while the next one will have random misfires and or a loss of engine performance and fuel economy.

The only 4.7 to come with a platinum spark plug came in the WJ Grand Cherokees with the 4.7 H.O.

What do you recommend?

 

[Joe.G]

I was having very similar issues and it turned out to be weak valve springs,I did full tune up, Factory O2 sensors new Cat's cleaned TB check everything and in the end I replaced the Valve springs and all was good in the world. 03 and 04 5.7 had issues with them. On your motor I believe they had known Head gasket issues but don't quote me on this.

 

[JohnnyMac]

Some good info given here. How many miles on the truck? So does it go away after the 5 seconds or does it continue after warming up?

I've seen where the the O2 sensor can cause throw this code. Forcing your engine to run too lean or rich from incorrect readings, which kinda makes sense because it happens after the engine warms up. I believe the ECU ignores the O2 sensors until the engine warms up.


I copied this from another site. You may or may not have seen it already and looks like you've already done a few of them. Good Luck and let us know if you figure it out.

A code P0300 may mean that one or more of the following has happened:

Faulty spark plugs or wires
Faulty coil (pack)
Faulty oxygen sensor(s)
Faulty fuel injector(s)
Burned exhaust valve
Faulty catalytic converter(s)
Stuck/blocked EGR valve / passages
Faulty camshaft position sensor
Defective computer
Possible Solutions
If there are no symptoms, the simplest thing to do is to reset the code and see if it comes back.

If there are symptoms such as the engine is stumbling or hesitating, check all wiring and connectors that lead to the cylinders (i.e. spark plugs). Depending on how long the ignition components have been in the car, it may be a good idea to replace them as part of your regular maintenance schedule. I would suggest spark plugs, spark plug wires, distributor cap, and rotor (if applicable). Otherwise, check the coils (a.k.a. coil packs). In some cases, the catalytic converter has gone bad. If you smell rotten eggs in the exhaust, your cat converter needs to be replaced. I've also heard in other cases the problems were faulty fuel injectors.

Random misfires that jump around from one cylinder to another (read: P030x codes) also will set a P0300 code. The underlying cause is often a lean fuel condition, which may be due to a vacuum leak in the intake manifold or unmetered air getting past the airflow sensor, or an EGR valve that is stuck open.

 

[Fast69Mopar]

What do you recommend?

I am a firm believer in using the stock spark plug or it's copper equivalent from another manufacturer if you have a preference.

The stock Mopar plug is a Champion RC12MCC4. At your local parts store the Champion 439 is the same spark plug.

Now, I have had great results over the years with the Autolite 5224. If you experience any detonation (spark knock/pinging) the 3923 works well to combat it.

 

[B17E1943]

Thank you.