1999 ram 1500 5.9 California emissions, continual p0304. Idle is rough but highway is smooth. New air and oil filters and oil. New plugs rotor cap and wires. Noticeable drop in rpm when unplugging 2,4,6,8 wires. About 30 rpm drop with each injector unplugged. 2,4,6,8 injectors ohm out 10-11 ohms. Edit Ignition tester is showing good spark on#4 as well (Stihl zat4)
New TPS about 8 months ago.

Not sure what I'm missing here have not done plenum. Plugs looked great except gap was wide from wear and not loosing oil. Any further direction would be great. Also attached is the freeze frame data from the dtc setting. Other 4 codes with 5 of 5 codes were from disconnecting injectors.

 

Time for a compression test.

 

Well before I did compression test I was looking at the battery terminals and realized the negative had quite a bit of corrosion. Cleaned both thoroughly, negative had lots of it between the terminal eye and chassis to body ground eye. Cleaned all this up and seems so far to have made a difference as well as resetting fuel trim in the computer having it Dc'd for a while. I have not thrown the code again yet nor has my infernal abs light come back on except startup test flash. Hoping this has taken care of it. Pulled 2,4,6 plugs last night and all looked good. Will do compression test this week and post the numbers as well.

 

Alright cylinders 2468
cold
2=151,4=125,6=150,8=152
Re ran after trying sea foam
2=155,4=143,6=155,8=156
Nothing obvious after removing valve cover to inspect.
Began to do wet test this morning but didn't realize everything needed to be warm.
Cel is on again and looking at the - fuel trim numbers from every time this thing has tripped cel I've been wondering if it has been a leaky injector.
Correct me if wrong but would the rise after decarbonization point to this as well?

 

Get any smoke at cold startup? How did the plugs look? Have access to air compressor? I would be tempted to run a leakdown test on number 4, to see just where the compression is going.

 

No smoke at startup, insulators white. Center and ground electrodes clean, except 4 with a bit of soft black build up. Only leakdowns I've done have been 2 cycle where it all get sealed up and then sprayed or dunked using a small mityvac. Then subsequent vac. Test. Could you explain or point me to a post that gives a good description of process? So many descriptions of procedures in the net at times it's hard to know which are good and useful also for my education the method of analysis of results. Thank you for you direction so far.

 

Example of leakdown tester.

Basically, you have two gauges.

Put the cylinder you want to test at TDC, in firing position. (both valves closed.) Screw the gauge into the spark plug hole, and apply air pressure. One gauge reads input air pressure. The other gauge reads cylinder pressure. A bit of math gives you leak down percent. I like to run input pressure at 100 PSI, then it is simply subtract cylinder pressure, and it yields percent leakdown directly. According to theory, up to 25% leakdown is 'acceptable'....... Seems excessive to me. I don't like to see anything more than about 15%, or, numbers that are VERY close across all cylinders.

Best part of the process is, You can HEAR where you are losing the pressure. It tells you pretty much exactly what is going on.

White insulators indicate running lean. Ideally, they should be kinda tan. The black buildup on number 4 indicates either running rich, or, burning some oil. (I lean toward running rich.... burning oil tends to lead to ash deposits on the plugs if it gets bad enough.)

 

Thanks ^ !

 

Status update.

No code no CEL back on as of yet after seafoam and new injector. Haven't had the $ to grab a leak down tester yet. Will update with results when I get one.
Debating on running another can of seafoam and rechecking compression again. Seems to be running much better at idle.

Unrelated vehicle. Got the rough idle smoothed out in the 94 f250 yesterday morning (known weak hydraulic lifter) that thing would shake like a tire was coming apart on you at 1200-1500 rpm

 

Sure wouldn't hurt to run some more seafoam thru it..... If it helped the first time around, its worth a shot.