2002 1500 4.7L Misfiring

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John Cee

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Ram Year
2002
Engine
4.7 Next Gen
Hello Ram fans. I'm new to the forum.

I have an '02 Ram 1500 4.7L with 216k+ miles on it. A couple of days ago, I filled it with gas and drove it 10 miles home. The truck was running normally; i.e. no CEL and smoothly although the fuel gage does not work. I parked the truck and 5 minutes later went back to start it. It started, but was running very rough--chugging and sputtering. I gave it some throttle but even at higher revs it was rough and skipping including the smell of un-burnt fuel.

The next day I conducted some tests:
*Fuel pressure is at 51psi at idle; the pressure holds for over an hour (the length of my test time patience) after the vehicle is shut off
*I checked for voltage at each COP, 13.5+ at each
*I fixed a leak in the PCV system; cracked hose behind left valve cover
*I found no vacuum leaks
*I ohmed out each injector: all are between 12.3-12.4 ohms
*There were no codes until I disconnected the #1 COP (to test voltage) and started the engine. After that I've seen a couple codes: P0201, P0463. I've disconnected/reconnected the battery several times since and P0201 has not reappeared.

I'm really not sure where to go from here. Any suggestions would be greatly appreciated. Thank you.
 

Fast69Mopar

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2004
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5.7 HEMI
Hello Ram fans. I'm new to the forum.

I have an '02 Ram 1500 4.7L with 216k+ miles on it. A couple of days ago, I filled it with gas and drove it 10 miles home. The truck was running normally; i.e. no CEL and smoothly although the fuel gage does not work. I parked the truck and 5 minutes later went back to start it. It started, but was running very rough--chugging and sputtering. I gave it some throttle but even at higher revs it was rough and skipping including the smell of un-burnt fuel.

The next day I conducted some tests:
*Fuel pressure is at 51psi at idle; the pressure holds for over an hour (the length of my test time patience) after the vehicle is shut off
*I checked for voltage at each COP, 13.5+ at each
*I fixed a leak in the PCV system; cracked hose behind left valve cover
*I found no vacuum leaks
*I ohmed out each injector: all are between 12.3-12.4 ohms
*There were no codes until I disconnected the #1 COP (to test voltage) and started the engine. After that I've seen a couple codes: P0201, P0463. I've disconnected/reconnected the battery several times since and P0201 has not reappeared.

I'm really not sure where to go from here. Any suggestions would be greatly appreciated. Thank you.
My guess without any further diagnostics would be a rocker arm slipped out. If you let it run long enough a misfire code will show up and then you will know which cylinder it is.

I would remove all of the spark plugs and inspect them for damage/debris, etc.

Perform a compression test and a leakdown test.

Another thing you can do, with the engine running, is disconnect each coil connector and one at a time disconnect each coil connector and see which one does not cause the engine RPM to change.
 
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John Cee

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Thank you, Fast69. Unfortunately I don't have a compression or leakdown tester, but I will remove the plugs and do the coil test.

I let the engine run longer after making the post and the P0201 code returned and a P0357 code appeared. I disconnected the battery, swapped the 1 and 7 COPs, reconnected the battery and the P0201 and P0357 codes both returned.
 

Fast69Mopar

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Thank you, Fast69. Unfortunately I don't have a compression or leakdown tester, but I will remove the plugs and do the coil test.

I let the engine run longer after making the post and the P0201 code returned and a P0357 code appeared. I disconnected the battery, swapped the 1 and 7 COPs, reconnected the battery and the P0201 and P0357 codes both returned.
I didn't realize that you had a P0357 DTC set. That is for the #7 ignition coil primary circuit. You either have a possible wiring issue or a PCM issue in my best forum mechanic voice.

Give the engine harness the wiggle test from the PCM to the ignition coils. Shake it down good to make sure there are not any chafed wires. Inspect the grounding locations for loose, broken or corroded grounds.

If swapping coils did not make a difference then I'd suspect a coil driver side from the PCM. Give the PCM the hammer test with a few good raps from the hammer and see if the misfire stops.
 
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John Cee

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I have a hammer! Thanks, Fast69. I will start with the PCM and wiring tests.

The thing that really throws me off is how sudden the issue occurred. No strange noises or odd behavior. Just wham, and it's running awful.
 

Fast69Mopar

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I have a hammer! Thanks, Fast69. I will start with the PCM and wiring tests.

The thing that really throws me off is how sudden the issue occurred. No strange noises or odd behavior. Just wham, and it's running awful.
One thing that must be remembered like I have over my 20+ year career as a dealership level tech...

If it has electricity running through it or moving parts it can and will break at any time. I learned a long time ago about what this really means.

PCM's stop operating correctly. Wiring gets old and brittle. Moving parts break. Metal fatigues. Just because it is new does not mean it is good. Things do just happen especially when we least expect it to.
 
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John Cee

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I appreciate the link, RLAF. Thank you.

Once the thunderstorm blows over, I'll get back to working on it.
 
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John Cee

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An update:
After going through the wiring and such I ordered a PCM. The price was reasonable enough to make it worth the risk. I'll report back after the PCM is installed.

Once again, thanks for the assistance.
 
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