Chrysler 300M Enthusiasts Club
  • P0306 code, replaced spark plugs and coil packs. Misfire detected on 6 code.

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Repair Questions and Answers.

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 #382053  by bobotech
 January 24th, 2020, 9:03 pm
My 300m is doing quite well except that it occasionally trips a CEL and the P0306 code. That is the code for misfire detected on plug 6. it never trips any other plug.

I have replaced the coil pack on 6 and replaced all the plugs.

Still it might pop the code like once a month or so. I reset it and it stays away. The engine runs great but you can on occasion feel a miss at idle in gear.

Anything else to look for besides the coil pack and the plug?

Thank
 #382057  by RobNJ
 January 25th, 2020, 9:04 am
Next step would be injector swap between cylinders. Have you tried some quality fuel treatment like Techron or even a dose of Stabil E85 to see if maybe it's fuel related ?
If still fails on same cylinder, then compression test and leakdown test. The intermittent part of your complaint doesn't lend to leakage but maybe you have just the start of the issue
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 #382072  by hrmwrm
 January 27th, 2020, 3:28 am
another slight possibility, is a slight coolant leak or vacuum leak in the lower intake manifold gasket.
coolant leaks in the corners aren't unknown in our engines.
get some carb/throttle body cleaner and spray around and see if it makes a difference.
probably easier to run some cleaner through the injectors first to rule them out.
like some lucas or seafoam.
you have to take the upper plenum off anyways to do injectors, and could replace the lower while there anyways.
hope it works out somehow.
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 #382083  by FIREM
 January 27th, 2020, 5:10 pm
Drain the coolant, disconnect the heater hose, remove the last few bolts and it’s off. You are minutes away once the fuel rail is out.
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 #382087  by FIREM
 January 27th, 2020, 8:53 pm
Recommend using Chrysler OEM lower intake gaskets. Design is better than aftermarket in the area where the water passages are.
Consider paid membership in the club. Member supported Knowladgebase has how to's with pics, torque specs , even videos of virtually every task done on our cars. Even factory book times are available so you can plan for how long it may take to do a job.
 #382125  by Countachqv
 January 31st, 2020, 11:58 am
I 2nd the guy recommending Techron for the fuel system. I use it in my Aston to keep the crap build up away and if good for that it is good for the M. Better than seafoam. I suppose your gas is fresh? if > 3months ensure you got the ethanol stabilizer. The Ethanol was created to increase cost and failure of older car fuel systems and reduce performances. That is why it is not use for private airplanes. Cold weather where you are?
Not sure about the coolant leak. May be sensors going out? Let us know what you find. I have an issue for 3 months last year like this. a pop of 30x each month at start up. cleaned up fuel and put oil cleaning additive , then it went away. Have had no car issues the entire year.