I have a cyclinder 6 misfire. Changed that plug 2 or 3 times, swapped the coil pack to number 4 saturday night and cleared the fault code. Sunday it came back with cylinder 6 so it's not the coil or plug. I have the ELM327 adapter and Torque Pro. The vacuum at idle is above 18, barametric pressure from truck shows right with my area and intake pressure and vacuum change as they should with throttle position and rpms. Air temp is consistent, catalytic converters show around 1,300 degrees while driving, both upstream O2 sensors are working right. Downstream sensors are constant between .6 and .8 volts unless I go to WOT and take my foot off they drop for a moment it .2 volts. Short term fuel trim is switching with the upstream O2 sensors. LTFT shows slightly lean on bank 1 and slightly rich to almost perfect on bank 2. Sensors seem to be ok. So I'm at the point of checking the injectors. Would it be worth it to pull the plug on 6 and see if it is showing a lean or rich condition before I take the fuel rail off. Should I allow several hours to take the fuel rail off and check them out? Because most of the time I am limited on my free time with work and kids. And any other insight to the problem is appreciated. I have read the diagnostic tests for misfires in the FSM.

 

You didnt mention inspecting the coils electrical connection. I would check the wires and pins going to that coil. Go back in the harness as far as you can. Or if you have a good meter with long leads. Ohm out the wires from the coil to the computer.

 

Nope I haven't made it that far. I guess that would be faster to rule out than pulling the fuel rail. That and the electrical connection to the injector. I also forgot mention the only time I notice the miss is at idle. It's a little rough. My RPMs on the gauge show no movement and on the Torque app they flucuate from the 660s to upper 680. And the truck seems sluggish unless I open the throttle. I read in the service manual that it turns the injector off to that cylinder if it does detect a miss. Does that mean the cylinder won't fire anymore as long as the computer detects the fault? Or does it turn it off momentarily to see if that corrects the problem.

 

here's the deal, you may have a stuck valve, go get some seafoam and run it threw the brake booster hose, follow the directions. once done, take it for a rip down the highway and see if things are better, I bet a bunch of carbon has built up

 

I prefer the aerosol seafoam through the throttle body. it's easier then sucking it up through the brake booster hose.

 

well for some reason my gmail isn't updating me with new mail so I am just now seeing yalls reply. I did buy 2 cans of seafoam at the advice of a co-worker. In the gas tank it really lowered my misfire count to almost non existent. I then dropped about 5 to 6 oz in the oil last week. A few days after I put it in the oil I sucked up another 5 oz through the brake booster hose which showed minor improvement. A week after I put it in my oil I changed the oil (yesterday). I could tell the oil was a little sludgy but not to the point it wasn't still fluid. This is where I seen the biggest improvement. Wow the difference in the get up and go. My next thing since I'm only misfiring at idle during operating temps is to clean the egr and iac. Torque shows that my EGR is still open at 0.8% sometimes during idle and 2 of the EGR test are coming back failed.

 

I think 12-14 ohms on the injector itself. Does your scan tool have a misfire monitor that you can read live?


In future endeavors with misfires, don't erase the codes after you swap cylinders with anything. This wipes out the misfire monitor AND the adaptives and it has to enable itself again, which takes time.

 

Thanks for the advice. I am able to read misfire conditions some what live. It updates the status like every 1 or 2 minutes so it's not instantaneous. I cleared the misfire codes a few days ago after I had tried something but cannot remember what. The P0300 and P0306 have not come back since but it is still misfiring a little. Here is the misfire conditions after I drove home from work, idling in the drive way (I only pay attention to the current trip misfire data as the first count for each cylinder is a 10 trip average). The misfire count never changes as long as i'm not sitting still idling. Once i start idling the truck starts to misfire. Also This is a very huge improvement from what i was getting. by the way I'm about 2.5 hrs from you in N.W. TN

MID:$a2 TID:$0b
EWMA Misfire counts (average) for last 10 drive cycles - Misfire Cylinder 1 Data
Max: 65,535Count Min: 0Count
Test result value: 1Count
PASS
----
MID:$a2 TID:$0c
Misfire counts for last/current driving cycles(calculated) - Misfire Cylinder 1 Data
Max: 65,535Count Min: 0Count
Test result value: 0Count
PASS
----
MID:$a3 TID:$0b
EWMA Misfire counts (average) for last 10 drive cycles - Misfire Cylinder 2 Data
Max: 65,535Count Min: 0Count
Test result value: 8Count
PASS
----
MID:$a3 TID:$0c
Misfire counts for last/current driving cycles(calculated) - Misfire Cylinder 2 Data
Max: 65,535Count Min: 0Count
Test result value: 0Count
PASS
----
MID:$a4 TID:$0b
EWMA Misfire counts (average) for last 10 drive cycles - Misfire Cylinder 3 Data
Max: 65,535Count Min: 0Count
Test result value: 0Count
PASS
----
MID:$a4 TID:$0c
Misfire counts for last/current driving cycles(calculated) - Misfire Cylinder 3 Data
Max: 65,535Count Min: 0Count
Test result value: 0Count
PASS
----
MID:$a5 TID:$0b
EWMA Misfire counts (average) for last 10 drive cycles - Misfire Cylinder 4 Data
Max: 65,535Count Min: 0Count
Test result value: 1Count
PASS
----
MID:$a5 TID:$0c
Misfire counts for last/current driving cycles(calculated) - Misfire Cylinder 4 Data
Max: 65,535Count Min: 0Count
Test result value: 1Count
PASS
----
MID:$a6 TID:$0b
EWMA Misfire counts (average) for last 10 drive cycles - Misfire Cylinder 5 Data
Max: 65,535Count Min: 0Count
Test result value: 0Count
PASS
----
MID:$a6 TID:$0c
Misfire counts for last/current driving cycles(calculated) - Misfire Cylinder 5 Data
Max: 65,535Count Min: 0Count
Test result value: 0Count
PASS
----
MID:$a7 TID:$0b
EWMA Misfire counts (average) for last 10 drive cycles - Misfire Cylinder 6 Data
Max: 65,535Count Min: 0Count
Test result value: 21Count
PASS
----
MID:$a7 TID:$0c
Misfire counts for last/current driving cycles(calculated) - Misfire Cylinder 6 Data
Max: 65,535Count Min: 0Count
Test result value: 2Count
PASS

 

If you're ONLY getting a misfire at idle, it's very likely you have a valve issue starting to appear. Maybe time for a compression test.

 

sorry for the late reply. It's not only at idle. I've noticed twice now at around 1,500 rpms going up a slight incline, it misfired and i could feel the hesitation. I don't have an IAC valve so that threw that out the window for possible idle misfire. I pulled cylinder 6 and 4 injector plugs. The plugs on the wiring harness side were discolored, and I wiped oil from number 4. I believe when i was filling the tranny fluid i spilled it on the plugs unknowingly . I hope i didn't screw up the plugs on the wire harness and only messed up the injectors. So i'm going to test them and see where i stand. I know a slipping serpentine belt or Crankshaft Potion Sensor can cause random misfires and the such. I've had the truck 2 years now and I'm on my second belt. The first time I just shrugged it off as it needed replacing and the dealership overlooked it. Now with the second one, the same thing is happening. It is squeaking or chirping if you will. So I need to address that too because some pulley is out of align or the tensioner is bad.