I purchased a 2006 dodge ram 1500 4.7 with automatic transmission about a month ago with around 202,000 kms on the clock.


It has what seems to be a misfire which is steady and consistent as soon as you start it in idle and also when driving at all speeds. Hasn't got better or worse and it's always present. You can feel a shake every second or so at idle and feel it missing as you are driving. Car is drivable but the misfire feeling is there.


No check engine light or codes are being thrown. I have cleaned out the IAC and throttle body and put injector cleaner through the tank. No difference. I changed the spark plugs to OEM copper mopar plugs. Didnt affect the misfire shake/vibration but the computer registered an additional 100+ kms for distance to empty which is a good thing and throttle feels slightly more responsive. Old plugs didnt look fouled or damaged in any way.


While I was doing the plugs, i also checked the resistance of each ignition coil which seem to be within spec (0.9 ohms). Not sure if that means they are definitely good?

Changed the oil and filter a few weeks ago to Castrol edge 5w 30 full synthetic.

Air filter is a K&N which came with the vehicle.

I have access to the Torque app and a bluetooth scanner and I have looked at the test results and it does show a 1-2 count cylinder misfire for a 3-4 different cylinders but I have checked a few times and it almost seems its random cylinders, not a specific few. Driving for around 10-20 mins each time.


It's got me stumped as to what it may be. The car starts first time. The the throttle is responsive when revving. No out of the ordinary noises. A slight ticking sound at startup which goes away after a few mins.


Any help or advice that can assist in getting to the bottom of this will be much appreciated!


This is my first post so please excuse me if I have missed anything.

 

Perhaps weak ful pump have you checked fuel pressure ? Maybe bad injector ? Also I had one a few months back get water in fuel and it did a lot of shaking an such and did not run very well,,dropped tank and could see water in fuel , flushed tank and replaced fuel pump an good to go

 

What do you suggest as being the best method to check the injectors?

I believe I can loan a fuel pressure gauge from Canadian Tire and check the pressure that way.

 

There are some you tube videos and some good write ups on how to check https://www.2carpros.com/articles/ho...-fuel-injector https://itstillruns.com/check-leakin...r-7760596.html
You can pull an do visual check on o-rings and for damage like stress cracks , I dont know best way but have to pull mine soon and will be testing my on soon

 

Thanks, some good information. I did a resistance test on the injectors yesterday evening and had an interesting result.

Of the 8 injectors on the vehicle, I had 7 of them come back at 13.6 ohms consistently. 1 injector gave me a reading of 12.9 ohms. Could this potentially be a culprit injector?

 

That's still within spec though....... Compression test?

 

I haven't done a compression test yet. What would be the signs of bad or low compression with these engines?

 

More than about a 20% difference from highest, to lowest, is bad.... and they all should be north of 100PSI minimum.....

 

Unfortunately, haven't been able to get hold of the tools yet required to check the compression or fuel pressure. The local Canadian Tire doesn't loan them but one a further away does so will probably pick it up on the way back from work tomorrow.

So I took the truck for a drive to pull some more data with the scan tool and export it into an excel spreadsheet. I created a second tab with 4 graphs representing the relationship between engine RPM with the O2 sensors and long/short term fuel trims. I am getting closer to understanding the issue, which almost seems like a rich running condition (I could be wrong).

Any help deciphering this data will be helpful.

 

Interesting. Looks like long term is adding fuel to bank one, but, subtracting fuel from bank two..... How old are your O2 sensors? What brand?