Multi-Misfire

Have owned my 2005 Ram 1500 Daytona Quad Cab for 3.5 years now. Love the looks and ride of the truck but it has been nothing but trouble since the drive home from the dealership. Current issue I am in dire need of help with is a multi-misfire (P0300). Engine misfires from abiout 1000-2000 rpm's and runs perfect above that. The misfire has fouled my bank 1 sensor 1 O2 sensor twice already, just installed another new one today. Strange thing is out scanner is showing misfires on the passenger side of the engine only (cylinder 1/3/5/7). If we disconnect the battery for awhile to reset the computer, the truck runs perfect for about 20-30 miles, then is starts the misfire again. My mechanic friend and I are just about out of ideas, here is what we have done thus far:

1. Wires replaced. No change.
2. Coil packs replaced. No change.
3. Plugs inspected, look perfect.
4. Fuel pressure on rail checked. Perfect.
5. O2 sensor 1/1 replaced due to fault code 3 times. Code gone each time but still have a misfire on 1/3/5/7 cylinder.
6. All harness inspected, wiggled while truck was running. No change.
7. Throttle body inspected, was clean. No change, harness also checked good.
7. Several ground wires were changed or cleaned. Both grounds running from the valve covers to the block were either not connected or loose with bad corrosion. Those grounds were replaced with heavier wire and grounded to alternator stud. 4 other ground wires were cleaned and reconnected. Better at idle but still has a misfire when performing a power braking test, misfire from 1100-1800 rpms or so, above that it's fine, below that it's fine. We also installed a ground wire to the throttle body, still no change.
8. Replaced cam sensor, no change.
9. Replaced crank sensor, no change.
10. Replaced EGR, no change

I had a misfire issue once before, had to replace a coil pack, replaced all plugs with Champion Copper OEM plugs (still good), an injector, and the gas pedal (sensor is known to go bad). I just ordered 2 more parts today, they should be in Tuesday:

1. Gas Pedal (again! This will be the 3rd on the truck)
2. Throttle Body

Only other thing we can think of if these 2 parts don't fix it is the PCM. Don't know why the truck runs perfect after a reset then starts misfiring again after 20 miles. Any ideas?

Thanks for any advice!

Keith in NJ

Wow, looks like you have covered most of the common cures. There are grounds wires located at the back of the heads to the chassis/negative battery. Check your trans fluid level and make sure it is spot on. The mis-fire code is caused by a sudden change in engine speed outside the acceptable range I believe between 1000-1500 rpm while in closed loop. CHK / CMK usually throw a code and a stumble can be felt. You have changed the sensors, A broken tone ring will also throw sensor code. If there is no damage to wiring harness, then it leads to the PCM. Have checked to see if there are any PCM updates? There is history with our trucks not playing well with anything other than OEM O2s. Welcome and let us know what you find.

Its sound likes you have an injector bleeding or clogging up. See if you can find an shop that does flow test on them and see. You are going threw O2 because the computer cant tell which one is bad so it cant fix the problem. With it just dumping fuel the will lean the bank in which it thinks has the problem. I had have the same problem on my 4.7 replaced the injectors and clear the problem. The filter in the top of the injectors was full of junk.

Redtruck-VA said:

Wow, looks like you have covered most of the common cures. There are grounds wires located at the back of the heads to the chassis/negative battery. Check your trans fluid level and make sure it is spot on. The mis-fire code is caused by a sudden change in engine speed outside the acceptable range I believe between 1000-1500 rpm while in closed loop. CHK / CMK usually throw a code and a stumble can be felt. You have changed the sensors, A broken tone ring will also throw sensor code. If there is no damage to wiring harness, then it leads to the PCM. Have checked to see if there are any PCM updates? There is history with our trucks not playing well with anything other than OEM O2s. Welcome and let us know what you find.

Click to expand...

Thanks for the input, will share with my mechanic friend. What is "CHK/CMK" ? What is and where is the tone ring? Not sure about clogged injector as ercmesser mentioned, runs like an animal above 2000 rpms, would think it would run crappy throughout the range, don't know.