You are OBDI, but, a decent scanner should be able to read a fair bit of data from it anyway.

Start with the basics, make sure your plug wires are good, and routed properly. If the backfire is consistent, I would take a long hard look at firing order. (I have had this problem before, checked firing order three times, and STILL had it wrong. Pulled all the plug wires off, and re-verified one last time to finally get it right.) If none of that makes a difference, time for a leakdown test. If you have a valve that isn't closing properly, that will give you what seems to be a backfire.

 

Have you checked the Long Term and Short Term Fuel Trims yet? Can you even check that with OBD1?

 

You can with the right scanner.

 

Yeah. I suppose most don't have a decent scanner. I use a Launch X431 Pro. I've got all of the adapters to go down to OBD1, but haven't even worked on an OBD1 car since WAY back! I'm sure I've never worked on one with fuel injection. I wasn't sure if the data feed on older cars showed the fuel trim. Bi-Directional scanners and Understanding fuel trim takes a lot of the guess work out of troubleshooting.

 

I dont have a scanner. I checked each injector with a noid light and they all checked out. 1 at a time, I pulled each plug wire to check for spark and see if I could pin point the misfire to one cylinder but all had spark and non eliminated the back fire. Did the same for the injectors. I did notice that the back firing isn't actually consistant. Sometimes its every 5 seconds, sometimes 10 sometimes 15. The low mile heads ran perfectly when they were pulled. Hard to imagine that a valve is stuck, but I guess it's worth a look.

It might be time to bring it in to a shop

 

Is it simply running too rich? Have you tried a power balance test? (I would guess that you already have, whether you know it or not. ) As you disable each cylinder, is the RPM drop consistent?

 

It does smell like it may be running rich, but because it bounces around so much at idle, it's hard to measure or even notice an RPM drop.

 

So start it up, let it warm to operating temp, and disconnect the IAC valve. Then try disabling one cylinder at a time, and see what the results are.

 

Here's an update:

took it to a shop, they didn't have a scanner for it and didn't seem like they knew much about dodge v8s. I picked it back up and took it to another guy who had the right scanner and said he had experience with these trucks. With all the snow and cold weather in Minnesota he got so backed up that he said I had to get my truck and bring it back some other time when hes not so busy. So it's probably been like 2 months since I've worked on it.

After some digging, I realized that the crankshaft position sensor from a 95 is different from a 97. One is an 8 volt system, the other is a 5 volt. I switched every sensor except this one so I'm gonna swap in the 95 crank sensor and maybe that will work!

 

The crank sensor ended up being the issue. Swapped a new one in and it fired right up! If anyone is swapping magnums around, just know that the 95 and earlier magnums use a different crankshaft position sensor than the 97 and later. One is an 8v system the other is a 5v. Also, the easiest way to get at the sensor is to take the plastic inner fender out and go through the wheel well. Dont waste your time going over the top.

now I just have to figure out my transmission problems... but I'll save that for another post.