05 hemi random cylinder misfire driving me crazy

[Hellendangerment]

When it's cold it will misfire and run very rough for like a mile then it's completely fine until I shut it off over night and it will do it again. The code says random cylinder misfire. Ive changed the plugs the wires pcv valve camshaft position and crankshaft position sensor. Cleaned the throttle body. Changed the oil cleaned the idle air temperature in the intake. Cleaned the fuel injectors off the truck and then threw cleaner in the tank. I am at a loss. Please help!!!!!

 

[preachp]

Hi Op,

Is it the same cylinders that are showing as misfiring? Could be a coil going out.

Hope you get it sorted,

preachp

 

[Hellendangerment]

It doesn't have a specific cylinder. Code P0300 random cylinder misfire

 

[RonJon '06]

Listen for a rattling sound behind the front cover, that would indicate a loose timing chain. If it was throwing lean codes before and now its misfiring I would suspect a bad front O2 sensor. If you replace it people seem to have better luck with the NGK rather than the Bosch. It might be time to do that compression test, that should tell you which direction to go.

 

[Hellendangerment]

Yea today I'm gonna replace o2 sensor and thank u I will keep that in mind. I did a compression test and all cylinders are at 150 first stroke.

 

[RonJon '06]

150 psi, well that's good news. It sounds like you're almost there.

 

[Hellendangerment]

Yea I just hope this is it. Thank u

 

[Redtruck-VA]

The 05 has waste spark wires, have you changed them? Are you using shorty's? Check for vacuum leak, check evap pump for leaking. Can sometimes suck fuel through it causing a rich stumble. Read about the conditions required to throw a misfire code. Believe it is above 160 degree's and between something like 1600-2100 rpm. Good luck...

 

[Hellendangerment]

Yes I changed the wires but I'm not sure what you mean by shortys but how would I check for a vacuum leak. I changed the egr valve and it only does it when I first start it up and idling it's fine but your right about the rpm that's when it does it but after I drive a mile it runs fine

 

[Hellendangerment]

Where's the evap pump located

 

[Redtruck-VA]

Shorty's are generally Taylor Shorty's, they eliminate the waste spark high tension wires and simply loop from the coil to the shared spark plug on the same cylinder. For some reason they break down in cold weather, boost and nitrous setups. This also can effect idle quality.
I misspoke when I said evap pump, I meant purge valve and it is located under the battery. It has two plastic hoses connected. These are prone to cracking from mostly age and heat. Engine off, try blowing in one of the vacuum lines and see if the valve leaks by.

http://www.moes-performance.com/Taylor_Thundervolt_8_2mm_Shorty_Plug_Wires_5_7L_He_p/ta3335bl.htm

 

[Hellendangerment]

Yea I saw that was wondering what it was I will check that today. Thank you

 

[Hellendangerment]

Changed the purge canister and evap pump and its still doing it. I'm gonna change all the coil packs next and after that I'm gonna be at a loss. Idk what else it could be

 

[Redtruck-VA]

When a individual coil breaks down it usually give a misfire code and cylinder. Even if the coils electrical plug becomes corroded it will still give a cylinder code. If you want to change coils, it certainly would be an opportunity to change to the 06 dual coils. But I don't think they are the problem. I'd make a list of what sensors affect the general operation of the engine and are not cylinder specific. crank sensor, cam sensor, MAP, O2s (front 2), throttle body and PCM. I'd check the connections and wiring. Then there is valve springs, which again usually give a cylinder. Exhaust leaks can affect O2s readings. Just throwing stuff out there. And as I mentioned before the trans fluid level seems to beable to cause a bad idle. Good luck.

 

[Hellendangerment]

Ok thank you.