Hello,new to the forum. Still haven't figured it all out yet, but trying. Have a problem with my 04 ram 5.7 it runs fin till you put your foot in it. Then it cuts out an throws a po300 code( mutable misfire).done a tune up, plugs,wires,egr,pcv cks. Still no change. Fuel pressure is 60 but will drop to about 50 when you gas it. Dies on cold starts, sometimes driving down the road. Was getting po335,po315 codes at first but not after tune up,just the po300 now. Thought it mite be a coil fail but not sure. What's a good way to check them? Any help would be appreciated.

 

is the truck 100% stock? or have you modified anything?

Another guy on here is having the exact same issue, and we have also replaced the Upstream O2 sensors which has seemed to help substantially.

He also checked all of his main grounds, and cleaned crud off the battery.

He also ran a compression test, which I suggest you do to make sure you don't have something more serious going on.

As for checking the coils, go look at the Hellllllp P0300 thread.. read through it and check off what you've done so far...

 

Welcome To The Forum.
You have just been served with the best info possible.
The AHHHHHH P0300 thread is going to be a abundance of help for you.

 

It all stock. It keeps giving me a (po335 cks ). I have replaced it twice already. Could it be losing signal? I checked the connection and it seems fine. What could cause that?thanks

 

That po300 thread was very helpful. Now I know ware to start. Thanks guys

 

So,will champion platinum plugs cause this misfire ?is it copper core only?

 

YES! Do NOT use Platinum! They are Garbage!

COPPER ONLY!