Replaced everything still have bad idle

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Oz Rivera

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Florida
Ram Year
2006
Engine
4.7
Hello I apologize that my first post is a negative one but I'm hoping with you help I can get this new truck fixed up and post cooler stuff later.

I have an 06 4.7 that I picked up for cheap cuz the motor was bad (no compression in cylinder 7 and 5) I picked up a working motor with 100,000 miles and replaced the following.

Coils
Injectors
Plugs
Oil Pump
Water Pump
Timing Job was done (Gears, Tensors, Guides and chain)
Rockers
Lifters
EGR
Camshaft Sensor
CrankShaft Sensor
MasFlow Air Sensor
PCV Valve
All Seals and Gaskets (except head gasket)
Entire Cooling System
Intake Manifold (Orignal was cracked)
Hell even replaced the motor mounts, alternator, belts and Power Steering pump

After all the this work I got the truck home drove strong and no misfiring under load butt has a misfire at idle. Scanned it and I'm getting the pesky P0300 code. Spoke to the mechanic who did the swap he said it could be the old gas in the tank (I know rookie mistake) So I've filled up 3 times and dumped cans of seafoam it got better but I still have a rough idle. Any ideas of what could be the issue, I'm guessing it could be a vacuum or fouled spark plugs from the ****** gas? Any other suggestions would be greatly appreciated.
 

CorDog009

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5.7
Pull a couple of plugs and see how they look. Vacuum leaks are easier to find with a can of brake cleaner..spray a mist around all the vacuum hose connections..if it idles up, there's a leak there.
 
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Oz Rivera

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Thanks Cordog for the tip never tries the break cleaner trick gonna tey tonight provide an update
 
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Oz Rivera

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Also another thing to note I used the Champion copper plugs dont know if that makes a difference maybe I should go with the Bosch Iridiums?
 

CorDog009

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I'd see how those are looking first. They might be ok. I think I went with one of the cheaper regular platinum plugs, I think Champion or NGK, can't remember which.
 

Oliver Closehauf

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Cummins 5.9
Does anyone know how the computer sets that code? Is it emissions or does it register a failed discharge from the coil?
 

Fast69Mopar

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Does anyone know how the computer sets that code? Is it emissions or does it register a failed discharge from the coil?
The way that the Chrysler programming in the PCM detects a cylinder misfire is from the crank sensor. The sensor utilizes a square wave pattern on the scope. For misfire detection the cranks sensor is looking for a crankshaft deflection. It's looking for a change in speed from the crankshaft so when a misfire is detected it changes the waveform of the crank sensor and then sets a corresponding DTC.
 

LoneWolf3574

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Hemi 5.7
The way that the Chrysler programming in the PCM detects a cylinder misfire is from the crank sensor. The sensor utilizes a square wave pattern on the scope. For misfire detection the cranks sensor is looking for a crankshaft deflection. It's looking for a change in speed from the crankshaft so when a misfire is detected it changes the waveform of the crank sensor and then sets a corresponding DTC.
I thought that was the purpose of the knock sensor? Or does the 4.7L not have those?
 

Dan98

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Test the vacuum with a gauge at idle and agean holding rpm around 2500 you should have the same reading for both with a steady needle if not maybe plugged converte and or vacuum leak. The computer will sense a vacuum leak and throw a code just cuz the lights not on doesn't mean there isn't a code

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Mntgoat

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Colorado
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I am going through the same issue. Good exceleration however come down to idle and, it runs rough. Intermittently to the point of a stahl.

I found a mechanich that will do a SMOKE TEST. Pumping smoke through the intake (while engine off).

It will pump all the smoke through the ventilation tube to detect leak.

What we saw was the tube thats a bout 30 inches long had dryrot cracks several places.

Get it done with a professional machine. You dont want to be guessing at what chemicals to pump through the system.
 
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