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Robert R
Robert R, ASE Certified Master
Category: Dodge
Satisfied Customers: 3933
Experience:  Dodge Master Certified, Dodge Sprinter Certified
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Son recently bought a 2010 charger rt w/ 5.7 hemi w/ 178k

Customer Question

Son recently bought a 2010 charger rt w/ 5.7 hemi w/ 178k miles. Runs a little rough and OBDII scan shows permanent P0308 code. Per consult with mechanical engineer at Chrysler we verified coil pack working, changed spark plugs, verified injector working and replaced injector. Local Firestone shop ran "diagnostic tests" and said it was definitely a weak valve spring. Per that shop, apparently, over 40+ mph the misfire condition goes away. Son changed both springs and valve seats on cylinder 8. Cleared codes and 0308 now pending once again. MIL for engine has not yet turned on. Do we need to allow for a few days of driving with the new springs before concerning ourselves again with the 0308? Also, PID for O2 sensors sae 0x15 (bank 1, sensor 2) and (bank 2, sensor 2) the short term fuel trim is pegged at 99.22% with no fluctuation. Other readings seem normal but also greek to a part-time, shade tree mechanic. Can send freeze frame or whatever if that would help.
Submitted: 1 year ago.
Category: Dodge
Expert:  Robert R replied 1 year ago.

Hello, welcome and thanks for asking your question. My name is*****'m a Certified Auto Technician with 28+ years experience. I will do my best to assist you. please keep in mind that I may need to ask questions of you before I can answer. When you reply please feel free to add as much detailed information as possible pertaining to your concern.

These are known for lifter failure causing the roller to stop rotating, this causes wear to cam lobes and begins flattening the cam lobe. Sometimes you will hear tappet noise, sometimes not. An easy test is to remove the right valve cover and disable the coils and crank the engine while watching all the rocker arms for full movement, If any of the rocker arms seem to be barely moving, you likely have a flat cam that will need to be replaced along with the lifters..

Keep me posted and let me know if you have any additional questions...

Thank you,

Robert

I also need to let you know that my responses may be delayed because I may be helping another customer, or I may be temporarily offline. Your understanding is greatly appreciated.

Expert:  Robert R replied 1 year ago.

Hello,

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Robert

Customer: replied 1 year ago.
I have been out of town and unable to work or worry about the car. We had already considered the flattened lobe option, which is why we took it to Firestone to have it checked. However, since the engine doesn't misfire at faster speeds, the local shop diagnosed with a weak valve spring. Seems like a worn lobe would cause a misfire all the time?
Expert:  Robert R replied 1 year ago.

A weak valve spring would have caused the misfire at higher rpm's as opposed to lower rpm's or idle. A failed lifter or flat cam lobe can definitely cause misfire at lower rpm's and less misfire at higher rpm's. another possibility is a sticking "MDS" lifter or solenoid. Either way, I'm leaning towards something with the cam or lifters causing this issue..

Expert:  Robert R replied 1 year ago.

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Thank you,

Robert...

Expert:  Robert R replied 1 year ago.

One more possibility came to mind, it is also possible that a vacuum leak exists near the #8 intake port. This could also explain the fuel trim being maxed out. to check this use soapy water solution and spray liberally all over the intake paying attention to the number 8 cylinder area. Any changes or engine stumbles could mean you found the leak...

Lastly, if they didn't reset the adaptive memory in the PCM you may have some residual issues caused due to this, the fix for this is to drive it a couple days then clear codes and pray for the best....

Keep me posted...

Thank you,

Robert