So just out of the blue one day while driving to work my truck starts to surge, backfire, buck, all while almost flooring the gas just to keep going. My first guess is that the o2 sensor is probably bad and the cat is probably plugged. I drove the truck a little bit on Sunday and the short trips it did fine. Monday morning on the way to work, I was about 10 minutes out and it starts the same crap again. After it sat 12 hours, it still ran like crap on the way home, didn't think I was going to make it. The codes I pulled were 12, 37 (I don't know why), 32, 32 (again, I don't know why), and finally 55. Any other ideas? i haven't noticed a lot of oil burn and I pulled only two spark plugs but they both looked ok, not perfect but not fouled or oil soaked. When the truck backfires, I hear it pop through the manifold.


1995 Dodge Ram 2500 4X4
5.9 gas engine
178K miles

 

How many miles? Fixed the plenum? Which plugs did you pull? Try checking 6 and 8.

 

178K miles


I pulled the two forward most plugs on the passenger side (on a Ford that would've been 1 and 2). Which two plugs are 6 and 8?


I've never fixed the plenum on this and I'm going to go ahead and assume it's never been done.

 

oh yeah I meant to add that it seems to "clean up" when I throw it in neutral and give it a quick rev, but once in gear, under load it goes to crap....

 

6 and 8 are the back two on the passenger side. Those are the ones that foul out first when the plenum is blown. (lower than the front, the oil goes to the back, and gets sucked in, and plugs up cats.)

Quick test: Pull the front O2 sensor (physically remove it from the cat) see if it runs any better.

 

Backfiring on EFI vehicles is often a secondary ignition problem. Wires,plugs,coil,cap n rotor. Plugs are 2,4,6,8 front to back, respectively, on passenger side. 1,3,5,7 driverside.

 

I recently replaced all the plug wires after a mouse went through and destroyed the coil wire, maybe I need to check the coil just to see if it suddenly went bad???

 

swapped ignition coil, O2 sensor, unplugged cat, checked plugs 6 and 8......no change..........


again only after driving for about 10 minutes or so, when you get on the gas, it won't downshift it just start to sputter, codes are still reading 12, 37, 32,32,55 in that order......

 

What did the two plugs look like?

 

plugs looked fine, not sooty, not soaked with oil.....they looked like a dry tan, but the truck runs fine for about 10 minutes or so. It's got to be something becoming heat soaked in my opinion, but I just don't know, it's frustrating cause I thought for sure that the coil would've fixed it. I'll try monitoring the fuel pressure next........