Could just be plug wires installed in incorrect order as well.

 

I'm out of ideas... I bought new plug wires and spark plugs, double and triple checked that they were in the correct order, same result. Bought a 95 ram 1500 AT engine computer, same result. Checked compression, about 140 psi at each cylinder when cold. Threw in the known good distributor and did the fuel sync with the voltmeter, same result...

My vacuum was at 15 in hg but every once in a while when the engine stumbled and backfired it would drop to 10 in hg. Could a vacuum leak be the problem? Or is this behavior the result of a poor running engine?

I'm stuck? The only two things that cross my mind would be 02 sensor or the crankshaft sensor.

it might be time to throw in the towel and take it in...

 

You should see 20in/hg at idle. You have a vacuum leak somewhere. Has the plenum been fixed?

 

I cleaned up the intake and put a new plenum gasket on but I didn't buy the hughes aluminum kit. I'm going to grab a can of carb cleaner and see if I can find the leak tonight.

 

The 5.9 magnum is a great choice, you can easily get 500hp w/o much effort/cost. There are at least a couple of how-tos on pulling a junk 5.9 magnum out of the junkyard and getting dyno'd 500+ HP from major car magazines on the internet. And if you care, you can make a magnum look just like a LA and fool 90% of the people that show up at car shows.

Backfire is generally the valve not getting closed before the cylinder is lit off. You could pull off the spark plug wires one at a time to help locate the issue. Since you have the old mopar, I'm assuming you have a timing light.... I'd try to see what the advance is looking like and if its stable. Then you can also buy a $10 ODB bluetooth adapter and check what the computer thinks the advance timing is with a $5 phone app. If you figure out which cylinder is the issue, I'd pull the valve cover and watch the valves - see if they are closing. Sometimes when a engine sits, valve guilds/stems can get sticky and cause issues.

 

Not if the plenum has a leak! I tested mine long ago(before i knew about the plenum issue)by putting a timing light on the coil wire and #1. Plenum was bad and when just a little throttle was given(in drive with e brake on) timing would cut out for a split second then you could clearly see the coil fire when it was not supposed to. Main problem i had was it backfired threw the intake not the exhaust. Hughes kit and it never happened again. The op should also try this with a timing light. Carb cleaner will work if the leak is on the outside.

 

See I did the Hughes plenum kit but I'm still losing oil, might be the plenum again

 

I did the hughes plate on my 96, as it was REALLY bad, and oil consumption was horrible. (quart every 100 miles or so.) After the fix, I was still going thru oil, but, "only" a quart every 150 miles or so. Of course, my truck had over 180K on the clock at that point as well. Thing is, the truck really don't smoke while driving..... and it wasn't leaking onto the ground either. I got some smoke at startup, so, I am sure the valve seals were at least a contributor, but, I think the majority was rings..... as compression just wasn't the best. (I think the truck was severely neglected by the previous owner.....) It's also possible that oil was leaking from the valve cover gaskets, but, would end up on the exhaust manifolds, and burn off there, never making it to the ground......

 

I know for a fact it's not burning it or leaking. I'm thinking it's the PCV valve because I also have a vacuum leak. I lose a quart every 1000 miles

 

Still struggling with this. Fixed an intake vacuum leak and I'm still having the same issues. Vac is up to about 18 before the engine starts to back fire and sputter.

Could a timing chain that's skipped a few teeth cause this?

Are there scanner tools that can look at sensor information that the computer has? This is a 95 so pre obd2 I believe.