Lethalweapon100
Senior Member
Hey everybody. 1997 ram 2500 5.9 V8...or V7.
A few months back i had an intermetent misfire out of the blue, it came and went. It would always occur on the highway at 70ish mph with OD on.
As of a few weeks ago it wouldnt run on cyl 8 for a few minutes in the morning.
As of a few days ago, it would take a good mile or two of gentle encouragement to get cylinder 8 to even start to fire.
As of yesterday, I would intermittently lose cyl 8 while I was going down the road.
I was getting a P0308 code and sometimes a P0304 would follow. Rarely a P0300.
It would misfire the most on the highway when I had less than 1/4 tank. Im talking hard misses with the classic super loud THUMP that comes with it.
At that point I realized i could no longer ignore it, I took an injector out of a spare 5.9 engine im rebuilding to drop in this truck. It did nothing to improve the issue. I put new O rings on the top and bottom of cyl 2, 4, 6 and 8 injectors and lubed them before installation.
The "new" injector measures similar resistance to the other ones. it says 10 ohms for all 2 4 6 and 8 injectors, but its a ****** HF multimeter that will probably read 15 ohms if i went and checked it now. The old injector, however, read 7 ohms.
After this "fix", the truck took 2 miles to even begin to fire on cyl 8. It would kick back off going down the road worse than yesterday.
It gave me a P0300, P0308 and P0304 again after my little test journey.
With the truck idling I began unplugging and prodding cylinders 8 and 4, one at a time. Injector 8 and 4 both still measured 10ish ohms, and the injector wires fluctuated between 3-5 volts for both 4 and 8. Like i said though, ****** HF meter.
After that, i was left with:
P0300
P0308
P0304
Injector 8 circuit
Injector 4 circuit
Injector 8 control circuit
Injector 6 control circuit (Did not touch cyl 6, at least not on purpose)
I dont remember the exact PCM codes for the last 4, but thats the description for them.
I rerouted the wires per the 1998 TSB, and the problem actually got worse. it makes a very loud pop from the exhaust under very light throttle when its in gear. Almost like a backfire, but not quite. definitely a hard miss. No codes as I cleared them before i started it after the wire reroute to see if the misfire went anywhere new, but it wasn't even driveable at that point. Ran like total crap.
Not sure what fuel pressure is. it doesnt have a schrader valve on the rail, so its a pain in the ass. It has a full tank though.
Thoughts? ideas? suggestions?
Edit: a few things to mention
It misfired on the highway as i stated, i did the plenum fix. Lasted a few weeks before it missed again.
Cyl 8 had spark according to my spark tester.
With a screwdriver to the injector, and my ear to the screwdriver, i can hear injectors 4 and 8 ticking away.
However, now that i started it for the second time after the reroute, im left with P0300, P0301, and P0308. What an exciting development. I ran it for about 30 seconds. It struggled to idle and almost stalled a few times.
DOUBLE EDIT: Plugs are also fairly new champions.
Sent from my SM-G920P using Tapatalk
A few months back i had an intermetent misfire out of the blue, it came and went. It would always occur on the highway at 70ish mph with OD on.
As of a few weeks ago it wouldnt run on cyl 8 for a few minutes in the morning.
As of a few days ago, it would take a good mile or two of gentle encouragement to get cylinder 8 to even start to fire.
As of yesterday, I would intermittently lose cyl 8 while I was going down the road.
I was getting a P0308 code and sometimes a P0304 would follow. Rarely a P0300.
It would misfire the most on the highway when I had less than 1/4 tank. Im talking hard misses with the classic super loud THUMP that comes with it.
At that point I realized i could no longer ignore it, I took an injector out of a spare 5.9 engine im rebuilding to drop in this truck. It did nothing to improve the issue. I put new O rings on the top and bottom of cyl 2, 4, 6 and 8 injectors and lubed them before installation.
The "new" injector measures similar resistance to the other ones. it says 10 ohms for all 2 4 6 and 8 injectors, but its a ****** HF multimeter that will probably read 15 ohms if i went and checked it now. The old injector, however, read 7 ohms.
After this "fix", the truck took 2 miles to even begin to fire on cyl 8. It would kick back off going down the road worse than yesterday.
It gave me a P0300, P0308 and P0304 again after my little test journey.
With the truck idling I began unplugging and prodding cylinders 8 and 4, one at a time. Injector 8 and 4 both still measured 10ish ohms, and the injector wires fluctuated between 3-5 volts for both 4 and 8. Like i said though, ****** HF meter.
After that, i was left with:
P0300
P0308
P0304
Injector 8 circuit
Injector 4 circuit
Injector 8 control circuit
Injector 6 control circuit (Did not touch cyl 6, at least not on purpose)
I dont remember the exact PCM codes for the last 4, but thats the description for them.
I rerouted the wires per the 1998 TSB, and the problem actually got worse. it makes a very loud pop from the exhaust under very light throttle when its in gear. Almost like a backfire, but not quite. definitely a hard miss. No codes as I cleared them before i started it after the wire reroute to see if the misfire went anywhere new, but it wasn't even driveable at that point. Ran like total crap.
Not sure what fuel pressure is. it doesnt have a schrader valve on the rail, so its a pain in the ass. It has a full tank though.
Thoughts? ideas? suggestions?
Edit: a few things to mention
It misfired on the highway as i stated, i did the plenum fix. Lasted a few weeks before it missed again.
Cyl 8 had spark according to my spark tester.
With a screwdriver to the injector, and my ear to the screwdriver, i can hear injectors 4 and 8 ticking away.
However, now that i started it for the second time after the reroute, im left with P0300, P0301, and P0308. What an exciting development. I ran it for about 30 seconds. It struggled to idle and almost stalled a few times.
DOUBLE EDIT: Plugs are also fairly new champions.
Sent from my SM-G920P using Tapatalk
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