PO305 code, misfire cyl 5

[snowplow]

Hey guys, I got a PO305 code and I can see in the live data that it is only misfiring pretty much at idle. I can tell it idles a bit rough. I have put new plugs everywhere and replaced #5 and #8 coilpacks just now. Still got PO305.

Swapped new #5 coilpack with old #7 and scanned. Still got PO305 so the new coilpack must be good. Cleaned the MAF out of desperation, tested #5,6,7,8 coilpack harness plugs with my power probe. Not sure what they should test like but I compared them all to see if #5 was different. All the same with 0v on one side and steady 14v on the other. Looked with engine running in dark and saw no arcing at plug or anywhere. Scanner says no fault on any injector.

I'm totally stumped now. Any ideas??? This is my first time using a scanner BTW.

THANK YOU FOR THE HELP!

 

[snowplow]

Hey guys, I got a PO305 code and I can see in the live data that it is only misfiring pretty much at idle. I can tell it idles a bit rough. I have put new plugs everywhere and replaced #5 and #8 coilpacks just now. Still got PO305.

Swapped new #5 coilpack with old #7 and scanned. Still got PO305 so the new coilpack must be good. Cleaned the MAF out of desperation, tested #5,6,7,8 coilpack harness plugs with my power probe. Not sure what they should test like but I compared them all to see if #5 was different. All the same with 0v on one side and steady 14v on the other. Looked with engine running in dark and saw no arcing at plug or anywhere. Scanner says no fault on any injector.

I'm totally stumped now. Any ideas??? This is my first time using a scanner BTW.

THANK YOU FOR THE HELP!

C'mon guys I'm stumped!

 

[Fix4Dirt]

the only thing I can think of if its not the ignition or fueling system would be a valve issue possibly? not sure, neevr had anything like this

 

[J_C]

I assume it was doing same thing before you replaced the plugs? If not, double check that the plug wire boot is completely seated on the plug.

Otherwise, I'd hook up a scan tool capable of live data, see if anything looks out of place but especially long term fuel trims, and would wonder if you have a clogged injector, might put some techron fuel system clean in a 1/2 tank of gas and run it a while.

Next would be a leak down or compression test, and next, pulling fuel rail, with a couple sets of injector o-rings handy to replace them on every injector, swap the position of #5 injector with another cylinder to see if the problem follows the injector.

 

[snowplow]

Yep it was doing it before.

I can watch live data on my scanner but I'm new to it so I'm not sure what 'normal' ranges are for most things. How would I find that out?

I have some injector cleaner in it right now.

 

[J_C]

Look at long term fuel trim first. Just as a sanity check, you might even swap #5 cylinder spark plug with another, or first pull it, hold threaded/cathode area to an engine ground area and see if it's making spark.

I'd also check fuel rail pressure. It might be that you're getting more misfires than just cylinder 5 but not enough others to trigger another code yet. Since it is only happening at idle, I'd also try cleaning the IAC if it hasn't been done in a long time.

OR... you could just wait a bit to see if the injector cleaner helps, though I'd hate to run it too long while dumping fuel into the cats, could damage them eventually. Then is when it comes time to see if the injector is getting power pulses, and consider swapping injector positions.