Hey guys, new to the forum! I did a drivetrain swap from a 1999 Dodge Durango SLT 5.9 4x4 auto in to a 1997 Jeep Wrangler TJ. After doing the swap and overcoming several obstacles, I almost have a great running rig.

For the back story, I bought the donor Durango totaled. It had been sitting for a few years, and had damage to the wiring harness. Cylinders 6 and 8 had the injector wires chewed through from a rat (sat in a barn/field for couple of years from original owner). Cylinder 1's spark plug was missing the tip completely. The oil was filthy, and the pan had tons of sludge in it. When I went and looked at it, it fired right off with the turn of the key and ran (with an obvious miss for obvious reasons). I figured it was just sitting neglected, but I bought it anyway for $500.

I replaced the valve cover gaskets, installed a Hughes plenum kit (it was nasty inside the intake manifold), rear main seal, oil pump (since I was already in there), timing chain cover, water pump, thermostat, breather hose, PCV valve, PCV hose, valve cover gaskets, oil pan gasket, intake manifold gasket, distributor cap, rotor, O2 sensors, cat/exhaust, headers, coil, spark plugs, and wires. Went to change the tranny fluid to find the dreaded broken snap ring laying in the pan. I got the transmission rebuilt and it's shifting great.

Before I did the plenum kit, I would hear a "ticking" sound under load (almost sounds like an exhaust leak or valve train noise). I then got a cylinder 1 misfire code, which led me to the plenum kit after opening up the throttle body to see it caked with suit and oil. After changing the plenum kit, the ticking sound appeared to go away but slowly came back after ~ 50 miles (I also swapped around the injectors to rule out a bad injector). Now it's back in full force, and it sounds like it's coming from the side with cylinder 1 again. After the ticking sound returned and a few operating temp/cool down cycles, my cylinder 1 misfire code came back. The code only seems to trip when idling for an extended period of time.

The spark plug from cylinder 1 looks to have some carbon, but not an extreme amount. When I did the rear main seal, I did see some obvious wear on the camshaft.

If you crank up the vehicle and drive immediately, it seems to run fine (with the tick/exhaust leak sound under load). If you let it idle for any period of time when cold, it idles fine for about 3-4 minutes, then starts very obviously missing and shaking. If you give it gas, it clears up. If it gets up to operating temp, it never does it again until it cools down. The misfire code will pop up even when the vehicle appears to running okay, but only when idling from a cold start.

What should my next steps be to diagnose the issue? I suspect a stuck/burnt valve on cylinder 1, but how can I be sure? It also sounds like air is being force back in the intake when it starts missing like that.

Here's a couple of videos showing how it's acting:
Cold start - Starts missing - Starts missing is about 2 minutes after cold start.

I'm not afraid to rebuild the motor, but do I need to? If it's valve work, would just rebuilding the heads be okay? The cylinders didn't look scored up at all, still had a nice cross-stitch looking pattern in them. The rear main bearing cap had very minimal wear in it (to my eye, didn't measure anything).

Thanks!

 

What brand O2 sensor did you install? I suspect a bosch...... (our trucks really don't like 'em, and coincidentally enough, the PCM starts paying attention to the O2 sensor after just about 2 minutes.....)

Unplug the front O2 sensor, and drive if for a few days. See if the code comes back, along with the idle problems.

 

Yep, I sure did use a Bosch O2 sensor. What kind would you suggest? OEM from dealership?

 

NTK from wherever you can find one for a reasonable price.

 

Thanks! Got them on order. I was looking everywhere else for the problem, but that makes perfect sense!

 

Drive with it unplugged for a bit, just to make sure that is indeed the problem.

 

Thanks. I will try it tomorrow and see how it does. Still going to keep the NTKs on order... holy crap googling about those O2 sensors, they need to go anyway!

 

You will find that the Dodges are FAR more picky about their sensors than just about any other manufacturer..... It's weird.

 

Thanks again HeyYou! I can't believe an oxygen sensor made that much difference! Idles way better, pulls better, and sounds a million times healthier. Now it does just sound like a header leak, I just bought the cheapest block huggers I could find.

They really should just stop selling the garbage Bosch ones.

 

Get some good header gaskets. Rem-Flex dead-soft copper, or aluminum. Should deal with the exhaust leak, unless its an actual hole in the headers.