OK, 2014 has been the year of Dodge truck for me. Bought a 1998 2500 that I had to get rid of within a month because we could not get it to run. Bought a 1999 2500 that I now run, but it's gonna need a new engine or a lot of work over the winter to correct the smoking issue.

Now I bought my son a 1997 1500 with a 5.2L. Not a pretty truck and definitely needs some TLC, but a decent winter beater for him. Drove it home without an issue, but noticed it was running rough. It's also loud as hell since it was missing a section of exhaust pipe in the middle of the system. Once we got it home, I was checking for the typical plenham issue (it has it) and noticed that one of the injectors was unplugged. Plugged it in and the truck seemed to run smoother, but it started to backfire on what seems like every firing cycle.

We replaced the injector with a new one, because it looked like it had been replaced before and I suspected that it may have been replaced with an injector out of a 5.9L. We thought that it might have solved the issue, but before we had a chance to really test it, we had an electrical issue kill the truck. Once that was resolved, we ran the truck and the misfiring came back. First, it was only at idle, but now it seems to do it more frequently.

I thought that the lose of back pressure may be contributing to the problems, so we replaced the missing section and got exhaust system whole and quiet again. Unfortunately, that did nothing to solve our backfiring issue.

We are getting a P0204 code, which indicates a problem with the #4 injector, but it backfires regardless of whether the injector is plugged in or not.

Can anyone give us some advise and paths to follow to help us resolve this issue. I've gotten opinions ranging from a problem with the ECM to maybe a burnt/stuck valve because of limited back pressure.

Looking to benefit from other people's experience and we appreciate any help we can get.

Thanks...LeLimoMan and his Son

 

Well we went back the garage last night and I now have some more info to ad to the post.

After more testing, we have determined that the backfiring only occurs when the injector is plugged in. In Fact, we are quite surprised that the truck runs pretty well on only 7 cylinders! LOL.

We swapped around #4 and #2 injectors to try and determine that the injectors were working properly. They are.

We pulled back a fair amount of the covering on the injector wires to see if there was any broken or frayed wires. All looks good up to the firewall.

We have pulled all the plugs on that side of the engine and the #2 definitely showed problems. It was wet with gas/oil. We also determined that all plugs were getting spark.

We also did a compression test on the even side of the engine and got a consistent 155-58 across all the cylinders.

Just for kicks, we disconnected the MAP sensor and the backfiring went away while the ECM was trying to relearn the proper air/fuel mixture. Once it corrected for not having the MAP sensor in the system, the backfiring returned.

So with this new and additional info, can anyone point us in the right direction or offer us advise on how to correct this problem?

Your help is MUCH appreciated,
LeLimoMan & his son

 

Well, after a lot of playing around with the truck, switching injectors, changing plug wires, testing O2 sensors and MAP sensors, we had just about given up. Decided that the truck ran pretty well enough on 7 cylinders that we would leave it that way and focus on other areas that needed attention to get the truck on the road.

Over the weekend, we had a friend's Honda prelude at the garage and it was throwing a misfire code and it was definateley lacking power. We changed the plugs, wires, rotor and cap and that solve its issue. It ran great and with no code. That got us thinking. We pulled all the truck plugs and cleaned and re-gapped them. We went to pull the distributor cap and noticed that it looked a little loose (not fully sure given the acrobatics needed to get at it). Anyway, we changed over the cap and rotor and cleaned up the cam sensor contact while we were in there. Put everything back together and fired it up. SUCCESS!!! The truck ran great with no backfiring and no codes.

This goes to show you that sometimes the hardest problems seem to have the simplest solutions.

 

Glad to hear issue was resolved.