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Greetings to you all! I am looking for insight and knowledge! I have a 02 Ram1500-manual. There has been many issues with running correctly.

*ALL sensors have been replaced with OEM -
*ALL coils and plugs are new
*once rpms have been brought above 1500rpms - truck drives pretty good. ONLY noticable issue right off is spark knock. Under normal driving, seems ok driver.

1. idle - Starts good. idles right for 10-20 seconds. Then it starts to drop a few hundred rpms then recover. 10 seconds later, drops... then recovers. SOMETIMES it drops so low it dies. New issue with idle after running for a min, service engine light comes on, starts running a little rough. Scan shows P0355,P0356,P0357 - Coils. (all new coils by the way)

2.IAC - When i unplug the IAC, other than Idling above 1,000 rpms, it runs better. Plugged it back in and idle returns to normal range along with the surging.

3. I have inspected the grounds that i could find. Pulled them, polished with sand paper. Found no bad wires. The ground straps are in tack and are clean and tight.

4. The Dealer says it has to be the TPS. More specific the ground. That ground touches everything. Just to be sure, I ran a new solo ground to the TPS. I clipped the harness ground at the plug, tapped in the new ground. This helped the idle a bit. The surge remained but only fractional. I then attached the factory ground wire to back feed the ground to the harness and the surge came back but worse.

5. I pulled the electrical fuse box to inspect. Found no bad wires, no loose wires. no corrosion.

Please lead me somewhere. Give me a area to look. Give me some specs that i can test against. Thanks, I am at my ends with this. :doh:
 

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UPDATE= I went out and pulled the grounds on the passenger side firewall. Cleaned, polished with sandpaper. looks like new. No change. One thing that blows my mind is when the truck is idling, I can pull the ground connection from the firewall ground post and nothing happens. Still runs? no change? What the heck? All i can think of is there must be a open wire somewhere that is grounding its self out. I also think there must be a area where some positive is back feeding into the ground. I can put my multi meter on the ground and he meter actually reads power. Very little and varies but none the less... It reads! I have traced wires. noting is jumping out. Wondering if it would be time and money spend better to just buy a new wiring harness?? I have many many hours and days searching for this issue. Thoughts???
 

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I am now looking for a new engine wiring harness. I have searched and searched. I am DONE! I think a new harness will eliminate the source. On the green/orange strip ground wire that feeds the coils and injectors that is grounded at the firewall on the passenger side; i read 12v when the truck is running. There has to be a wire touching or connection that is being made somewhere. It blows my mind that it will still run with power on the ground side! Any ideas for a reasonable source for a complete engine wiring harness?? Any post would be appreciated.
 

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Sounds to me like you have a short some where on the shared ground. I had a similar issue and cut the ground at the PCM for one sensor to replace it and found it was shared with about 12 other sensors all spliced in throughout the harness. I managed to replace most of the 5v power supply wires for these sensors, or at least the bad ones due to a short, then tap back into the ground that was in the harness, and it worked. This was on a 5.7L however so not apples to apples. I do think that most of the same wiring is for both 4.7 and 5.7. If you can try to look up the testing procedure for verifying correct ground and voltages for each code you're getting and work back, I'd also check the Crank, Cam, MAP, Coolant Temp, and air temp sensors as I think they all run on the same power/ground circuits. It's time consuming, took me two weeks to get it all figured out, hope this helps.
 
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