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Discussion Starter · #1 ·
About a year ago I kept getting P0300 random misfire codes, about 1-3 times a week, after initial start it would surge and shut off upon first full stop (at stop sign by my house). I replaced all spark plugs and coil packs, found one spark plugs broke in half, but problem continued. I then replaced the fuel pump and the issue went away, problem is it has now started to hesitate to go after each start until I put the truck in neutral and rev engine a couple times, if it hesitates long enough it gives me a P0300 code again. Does anyone have any insight on this? Is this a typical issue with these trucks?
 

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Wish I could help.. but lets hope it's not the cam/lifter issue like on Hemi's.. If it is ... Do you have a noticeable tick at idle?
Unfortunately the 4.7 has a worse reputation than the Hemi. Especially valvetrain issues.

Hesitation is an odd symptom on a fuel injected engine. Maybe a sensor is making it run rich or lean. Maybe pull a couple plugs and look at them?
 

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1966 Crown Coupe, 2016 200 S AWD, 1962 Lark Daytona V8.
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Are the spark plugs the correct Champion RC12MCC4?
 
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How many plugs did you change? Upper and lower banks?
 

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. . . . About a year ago I kept getting P0300 random misfire codes, about 1-3 times a week, after initial start it would surge and shut off upon first full stop (at stop sign by my house). I replaced all spark plugs and coil packs, found one spark plugs broke in half, but problem continued. I then replaced the fuel pump and the issue went away, problem is it has now started to hesitate to go after each start until I put the truck in neutral and rev engine a couple times, if it hesitates long enough it gives me a P0300 code again. . . . .
Does this hesitation only happen after the engine is fully warmed up? If YES then I would suspect that one or more fuel injectors on bank 1 or bank 2 is dumping excess fuel into the cylinder intake. With the engine management system in closed loop operation, the upstream oxygen sensor for the offending bank will report an extra rich air-fuel mixture. The engine management system tries to get the cylinder bank back to stoichiometric (chemically balanced) state but cannot do that. It keeps reducing fuel injector pulse time to lean the air-fuel mixture such that the other cylinders start to misfire for a too lean condition. This causes the random misfire code P0300.

Look at the upstream oxygen sensors for bank 1 and bank 2. If one sensor shows a consistent -10 to -20% fuel trim while the other oxygen sensor oscillates around 0% that is the clue. You will need to do an injector balance test and determine which one is allowing excess fuel to discharge.
 

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How many plugs did you change? Upper and lower banks?
I believe 2005 is only an 8 plug motor, 2008 up are the 16 plug motors.
 

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Discussion Starter · #8 ·
I replaced all 8, it's only on start-up (up to 2-3 minutes after starting), once it gets going I have absolutely no issues until it's off for a bit, even if only for 10 minutes, it will struggle again after starting as stated in parentheses.
 

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No, I put Bosch Platinum plugs in because I was told it didn't matter.
Believe it or not, it does matter. I've had issues where Bosch sensors and such did not play well with MoPar's. I'd put the correct, recommended plugs in and I'll bet no more misfire codes.
 

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All plugs, and coil packs were replaced about a year ago.
Perfect time to pull them again and see how they look.

And to get rid of the Bosch plugs.
 

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. . . . I really feel like it's a fuel delivery issue, the same problem went away after replacing fuel pump, but a fuel pump should not start failing after only 1 year. . . .
Have you investigated fuel trim values for upstream oxygen sensors, bank 1 versus bank 2? Post #6. Lean air-fuel mixture can cause a misfire besides spark plugs and plug wiring.
 

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I really feel like it's a fuel delivery issue, the same problem went away after replacing fuel pump, but a fuel pump should not start failing after only 1 year.
Unless it is an Airtex fuel pump. They were notorious for being bad right out of the box. That may have changed, but the last fuel pump I had installed was a Carter. Shop said they called Airtex pumps "Yo-Yo's" since they were having to take them out right after installing them or shortly thereafter.
 

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Discussion Starter · #16 ·
Perfect time to pull them again and see how they look.

And to get rid of the Bosch plugs.
Just replaced plugs with Champion Copper OEM plugs, ended up replacing all coil packs too as half the plugs had rubber stuck to them and a spring fell out of one. As of this moment, it's running perfectly. I was told platinum last longer, but I recently found out that they don't have the temperature control that the copper does.
 

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Discussion Starter · #17 ·
Unless it is an Airtex fuel pump. They were notorious for being bad right out of the box. That may have changed, but the last fuel pump I had installed was a Carter. Shop said they called Airtex pumps "Yo-Yo's" since they were having to take them out right after installing them or shortly thereafter.
I'm not sure, I just know it was an OEM replacement.
 

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1966 Crown Coupe, 2016 200 S AWD, 1962 Lark Daytona V8.
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The problem was likely all in the wrong spark plugs. It does matter.
If they were purchased fairly recently, many auto parts stores will exchange them rather than having an upset customer. Some vehicles can tolerate platinums instead of coppers, some not so much.
Always use OEM replacement parts for best results. I have seen wording like: 'OE-style' that bothers me.
Aviation and drag racers still mainly prefer copper-nickel spark plugs. There are articles on Google about the differences, advantages and benefits of electrode materials. Heat conduction is a big factor.
We also have the 'miracle' Iridium and Ruthenium plugs (beware of the Marketing department claims!)
Lots of Chrysler engineering lab resources, time and money goes into selecting the optimum ignition 'burn' for a particular engine.
 
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