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Jerry, Master Mechanic
Category: Dodge
Satisfied Customers: 1754
Experience:  ASE Master tech, 30 years exp. troubleshooter, driveability tech
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Misfire cyl 3 Dodge 4.7
, check engine light, code

Customer Question

Customer: misfire cyl 3 Dodge 4.7
JA: Thanks. Can you give me any more details about your issue?
Customer: check engine light, code P0303
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Submitted: 1 year ago.
Category: Dodge
Expert:  -Brad- replied 1 year ago.

Good morning and welcome to JustAnswer!!!

I see that you have a cylinder #3 misfire, but what have you done to correct it? If nothing then I would swap coils, spark plugs, injectors, until the misfire moves and then replace that component..

Let me know what you find,


Customer: replied 1 year ago.
little history on the engine. has 150,000 miles. at 120,000 lost a valve seat, had both heads done.I am throwing a p0303 code, I've replaced plugs, coil packs, pulled injector - cleaned and then swapped with another.
did compression test on the left bank, I got 145, 140, 130 (cyl 3), 140
Customer: replied 1 year ago.
Running compression test gave me on cyl 3 idle 50 and snap acceleration about 92
I have removed the valve cover also to check for broken springs - Look good
Expert:  -Brad- replied 1 year ago.

I see you wrote this:

did compression test on the left bank, I got 145, 140, 130 (cyl 3), 140

Are you testing the 3rd one back on drivers side as cylinder #3? If so then #3 is the 2nd one back on the drivers head.. Drivers head is 1-3-5-7, pass 2-4-6-8.

Customer: replied 1 year ago.
no that was back to front..... and I'm sorry its P0304 so cyl 4 is 2nd on pass side... that is what I am working on
Expert:  -Brad- replied 1 year ago.

And #4 is 2nd from the front on the drivers side, so you have swapped coils-injectors-spark plugs and it still misfires? Is it dead cylinder or intermittent misfire? If you grab a test light is the coil and injector receiving proper ground pulse from the PCM?

Customer: replied 1 year ago.
used a noid light. both getting pulse.
Expert:  -Brad- replied 1 year ago.

I'm sorry I posted #4 is 2nd back on drivers, and I meant to say passenger side.. And is this a dead cylinder?

What is compression of #4 and are you using Champion plugs?

Customer: replied 1 year ago.
130 and I believe champions...not really sure. what would the brand have to do with a misfire?
Expert:  -Brad- replied 1 year ago.

Because I have had Independant shops bring misfires into my dealership and the problem was they used Autolite plugs. Once I installed Champion the misfire went away...

Customer: replied 1 year ago.
I've swapped plugs between cylinders, old and new -
wouldn't the problem follow?
Expert:  -Brad- replied 1 year ago.

Yes and if it hasn't moved your issue isn't the plugs.. What year model do you have and is it a dead misfire or intermittent? Since it's 130 and the rest are 140 I would perform a leakdown test to see if you have an issue with the rings or valve seats. Which cylinder did you have an issue with valve seats?

Customer: replied 1 year ago.
2002 and I don't believe its a dead cylinder, idols rough, not horrible and it runs smooth when driving. Nothing noticeable in much power loss.
Expert:  -Brad- replied 1 year ago.

If it's not a dead cylinder then yes I would perform a cylinder leakdown test to see why it's lower than the rest..