Misfiring and can’t seem to find the problem on 4.7

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rsancheztx220

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Okay so I have a problem with a code p0300 which i recently found out that cylinder #1#3#5#7 is misfiring but cylinder #2#4#6#8 is firing with no problems and can’t seem to find the problem. I replaced the spark plugs and recently just replaced the lifters and rocker arms but the spark plug change didn’t seem to do anything, both the coils and fuel injectors are getting power but it still seems to Misfire. I’m alittle lost on this one and can’t seem to find a answer’s anywhere on the web. even when I disconnect the coil and injectors one by one on the cylinder that are misfiring nothing seems to change but the cylinders that are not misfiring when I disconnect anything, there is a change of idle which I assumed those cylinder are firing correctly. any help is appreciated thanks.
 

RamRod37

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my first test would be a exhaust back pressure test on the bank misfiring sounding like stopped up catalytic converter. If there are no other codes but misfire that is where I would start cause 85% of the time that is what it will be if it has one on each bank.
 
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rsancheztx220

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There is no there catalytic converter on the truck it’s a straight pipe to a flow master muffler
 

mrbigbill

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So, dodge 4.7s in that year had problems with micro cracks forming on the plug right where ceramic meets the metal base, I did read you changes plugs, I went through 3 sets myself, 1st 2 sets where from AutoZone and where champions, seems like AZ had some problems with a run of champions, try oriely or whatever you have and get a good set of plain non platinum NGK, both sets of champions cracked as soon as got to operating temp, hard to see but usually you'll see a small grey line in insulator right above where ceramic and metal base nut meet....the NGKs got about 20k on them before same thing ......also, worth a try and replace crank position sensor, using a scan tool mine was throwing wierd peaks only when one side of engine fires, new sensor cleaned up profile, but dime to a dollar plugs about every 20-30k
 

EdGs

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Check ground on that cylinder head. Long shot, but you never know.
 
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rsancheztx220

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I checked all grounds in the engine bay from the cylinder heads and to the engine block and they all them seemed good with no damage to them, and I also swapped coils from the side that’s not misfiring to the one that are and nothing happened i even installed two new coils on the side that is misfiring and still nothing , I installed autolites iridium xp and it seems to run better but cylinder #1#3#5#7 are still misfiring. I checked the wiring harness and there no damage or short anywhere everything is getting voltages the only things I’m think is that it might be a bad pcm but still not sure. everything so far looks good but still can’t seem to find a answer , I’m going to hook a scanner to read the data coming from both coils and injectors and see if I see anything odd. And I also check the valves seats and springs on the heads and they seem good and work correctly. I checked for vacuum leaks and there no leaks anywhere. Check Compression and everything is good . I’m still alittle puzzled on the situation.
 

pacofortacos

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Sorry, I see that you checked compression. Both banks identical.
Have you done anything with the cam or timing chain?

If there is a ground to the coils and injectors, the only things left on those is the wiring to the PCM and the PCM itself.
 
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pacofortacos

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hopefully these come through - from a 2001 dakota manual
 

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rsancheztx220

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I haven’t done anything to the cams or the timing chain I bought the truck from someone as is and haven’t done the timing yet but today I took off the valve covers to check the timing on the cylinder that is misfiring and the cam gear is one tooth off and is not at 12 o clock it’s at 11 o clock and everything else is timed correctly the other cam is at 12 o clock and cylinder #1 is at TDC at the 2 o clock position where it should be . I’m honestly thinking it could be that . since everything electrical is working correctly which I spend 3 hours checking everything from the fuse box to the harness itself.
 

pacofortacos

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I haven’t done anything to the cams or the timing chain I bought the truck from someone as is and haven’t done the timing yet but today I took off the valve covers to check the timing on the cylinder that is misfiring and the cam gear is one tooth off and is not at 12 o clock it’s at 11 o clock and everything else is timed correctly the other cam is at 12 o clock and cylinder #1 is at TDC at the 2 o clock position where it should be . I’m honestly thinking it could be that . since everything electrical is working correctly which I spend 3 hours checking everything from the fuse box to the harness itself.
Might just be as simple as that cam being off - now the question is why is it off?
Is it off because someone was in there or do you have broken chain guides?
If it looks like someone was in the front end of the motor, it might all be ok and just need timed. If not, I would probably go in and check everything - broken guides can get ugly quickly.
 
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rsancheztx220

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the last person who owned it worked at a shop and said he did all the work on the truck himself and don’t get my wrong there was a lot of problems I found when I first got it but there could be more issues I may not know about but I’m eventually going to replace everything on the timing and do a head gasket job on it . I just need it fixed for the time being since I’m going to collage but this my 3rd dodge with a 4.7l and I haven’t seen that before where it’s not timed right. I’m assuming he probably did the timing and didn’t timed it right but who knows to be honest I haven’t touch anything on the front end of motor besides change the lifter and rocker arms since the lifter we’re making that tick sound and the spark plugs but hopefully fixing the timing does the trick for the time being.
 
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EdGs

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Has someone worked on the timing on it, or did they use parts from a 4.7 from a different model year 4.7 or from a 4.7 in another model vehicle?

The reason I ask is that there is an there are 2 different 4.7 engines, and they are only slightly different. One is a JTEC, and one is an NGC type. In the 1500's from the 2002 model year was when they had both.

I know yours is a 2003, which should be an NGC type engine. The tone rings on the crankshaft are different with 32 teeth on the tone ring of the NGC vs 16 teeth on the JTEC, as well as the reluctor? on the passenger side camshaft sprocket (a different window pattern).
 
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EdGs

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Here's my '02 4.7 at TDC. Disregard the colored links. I was so excited I had the timing set installed that I forgot to take the pic before I rotated the engine through a couple cycles, lol.

20190414_181458 (2).jpeg

Below are the 2 different camshaft sprockets.
20220925_230342.jpg
20220925_230315.jpg
From the RockAuto site for 2002 model year.

You can see the difference in the window pattern on the passenger side cam sprockets of the 2 types.

A little harder not knowing exactly what has been previously done on your engine.

Hang in there.
 
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rsancheztx220

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I appreciate all the information this morning I double checked the cam gears and both cam gears are correct. since you mentioned about that. I also looked at a pic on a mopar parts site for the NGC cam gears and both were spot on.
 

Elkman

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With a misfire on a modern engine with electronic ignition the very first thing I would have done is check all the plug and coil wires with an Ohm meter.
 

Sherman Bird

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I checked all grounds in the engine bay from the cylinder heads and to the engine block and they all them seemed good with no damage to them, and I also swapped coils from the side that’s not misfiring to the one that are and nothing happened i even installed two new coils on the side that is misfiring and still nothing , I installed autolites iridium xp and it seems to run better but cylinder #1#3#5#7 are still misfiring. I checked the wiring harness and there no damage or short anywhere everything is getting voltages the only things I’m think is that it might be a bad pcm but still not sure. everything so far looks good but still can’t seem to find a answer , I’m going to hook a scanner to read the data coming from both coils and injectors and see if I see anything odd. And I also check the valves seats and springs on the heads and they seem good and work correctly. I checked for vacuum leaks and there no leaks anywhere. Check Compression and everything is good . I’m still alittle puzzled on the situation.
You need more diagnostic equipment. A Scanner is merely a monitor for the computer in the vehicle. DTC's are only designed to get you directed to the area needing help, and are DEAD wrong many times. Phantom codes will have you running in circles.

It's time to get a good DVOM and check for voltage drop across all positive battery and negative battery connections, ESPECIALLY grounds with the truck warmed up and highly loaded.... A/C on high, headlights on. Next, check for A/C ripple voltage coming out of the alternator.... AT THE ACTUAL STUD on the alternator where the wire goes from the alternator to the battery. It should not be higher than approx. 100 millivolts. I like to see under 90 mv.

An oscilloscope is next up. Check for a damped wave pattern on the electrical system which indicated coil secondary bleed over from any one of the coils. Also, you need to determine how much amperage each coil draws on the primary side.

I'd be looking for something germane to those cylinders together, such as a splice shared by B+ by all the coils on that bank or for shared B+ on the injectors. A ground shared by multiple items can certainly be the issue.

A high amp clamp hooked to a scope, on the negative battery cable with the direction arrow pointed to the battery and performing a relative compression test and saving the wave form is next (Done by flooring the throttle to go in to clear flood mode and cranking for 10 seconds at least). This really loads the coils because they are firing on high compression and no fuel. Zoom in on any spikes that go up very high. These show misfire bleedover from coils in a lot of cases.
 

Ole Buck

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With a misfire on a modern engine with electronic ignition the very first thing I would have done is check all the plug and coil wires with an Ohm meter.
THIS. I chased a miss for a week. Finally got the meter out and pulled every coil off and tested it. had 7 doing perfect and then one said nope aint happening. I changed everything from plugs to the fuel pump and the whole time it was a coil with a broken wire inside that was jumping around.
 
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