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Hi all,
This is my first time posting on here, I am having some issues with this P0303 code.
The truck in question is:
2010 Raptor 6.2L

Compression Test on Cylinder #3 168PSI
Compression Test on Cylinder #2 170PSI... Seems orderly to me.

New plugs... Did nothing

Changed Coil pack from #3 to #2... still getting Cylinder #3 misfire.

Sea foam has seemed to get the truck to "Idle" at around 575-625RPM but still with a noticeable misfire. Before the sea foam it would stumble between 400-1,000RPM and couldn't seem to make up its mind. I ordered a new injector for #3 and it should be in today. Does anyone have any ideas here? I do not have I noid light to check the injector, Replacing it at $48 seemed like better idea I guess.

Thank you! hopefully someone can help me out here. The local dealer cant figure it out.
 

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I wouldn't really worry about the noid light, there are separate circuit check codes that are pretty robust if the wiring was the issue, though I will admit that isn't always robust to intermittent connection issues that doesn't sound like your problem. I would be willing to bet it's the injector since you already went and proved out the ignition.

If you wanted a quick check(while waiting on parts) you could swap injectors on 2 and 3 and see if the problem moves. Otherwise you may need an obd reader to start looking at the short and long term fuel adders and the lambda reading from the oxygen sensor
 

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It looks like you've ruled out the mechanical with the compression test. RoushDriven is correct on moving the injector to isolate the problem. Take care with the seals though; they get brittle and can break and leak.

Have you moved the wire to the bottom sparkplug? There are two sparkplugs per cylinder; both are fed off the coil-on-plug but one is on top and the other down low on the block near the exhaust manifold. Here is a diagram:

upload_2018-9-15_11-42-50.png

Only do one operation at a time or you will get unclear results. Move the wire on nbr 3 from the coil to plug to an adjacent cylinder and see what happens. If the code moves, replace the wire; might not hurt to do them all because if one fails the others can't be far behind unless you see damage to it from contacting something.

The last thing I can think of to try if that doesn't reveal the issue would be to move the plugs on 3 to an adjacent cylinder unless inspection reveals damage. Take care to remove the plugs carefully as I think the heads are aluminum and threads might come out with the plug.

Clear the code after you do each step to see if it returns.

Good luck with this,
LZinAZ
 
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