First and foremost, hello everyone. Long time forum user for good information, first time poster.

I have a 1996 dodge ram 1500 5.2 auto with roughly 170,000 miles. I bought the truck knowing it needed some work. Had a bad miss. Having owned many of the 3.9,5.2,5.9 engines I was shooting for the plenum gasket. Took it apart. Worst I've yet to see. Was idling at 2500rpm and pulling vacuum through the breather with the iac closed. So I got everything squared away with that. Started the truck and the high idle is gone, but the bad miss is still there.

In an effort to track down the miss I replaced the plugs, wires, rotor, and cap. Same story. So did a compression test. All were above 125 besides #8. It read in at 30psi. A wet compression test revealed it was not bad rings. Did a leak down and at TDC #8 the air was coming out in vast volumes through both the intake and exhaust. So I started the engine with the valve cover off to check the function of the valves. They looked normal. But out of curiosity I took the rockers loose. This sealed up the cylinder on the leakdown test. No more air coming out the intake or exhaust. So I torqued the rockers back down and noticed that both valves have pressure on them and are open a little. Leakdown was bleeding through exhaust and intake once again.

The valves are moving and don't seem to be bent or lifters stuck. If I take the rocker arms off it seals right up. Push rods are the same as any other cylinder so they are the correct length.

Anyhow, I am at a lost here. Any ideas would be greatly appreciated. I hope I am just overlooking something simple.

 

Lifters not bleeding down?

 

I honestly don't know. I assume being a hydraulic lifter that it shouldn't bleed down during normal operation? Are you suggesting the plunger may be stuck at the very top of the lifter causing too much preload on the valves? I have rislone in the engine now. Lose oil pressure after extended higher RPM's which leads me to believe the engine is very gunked up. (Another problem I have seen multiple times with these engines.) so maybe it is stuck? Any way to cure this easily?

 

About the only way I know to cure it permanently, is to replace them, and thoroughly clean the engine while you have it apart.

Hydraulic lifters are designed to take up the valve lash, but still allow the valves to completely close, without having to adjust them ever 10K miles..... I suppose, another option would be adjustable rockers..... but, you are lookin' at over 300 bucks there.... and if the engine is really dirty..... you may just be postponing a larger problem.

Given your oil pressure symptoms, I would be REAL tempted to drop the oil pan, and see what interesting things you find in there. If your truck is a 4x4, you don't even need to raise the engine to get it out.