Flyinbrian

There is a technical service bulletin out on this one.
I had the exact same problem on my '98 360.
Octane boost, injector cleaner, all this will not fix it.

You have an intake plenum leak. Oil is getting sucked out of the lifter valley and onto the plugs. The oil is in the fuel/air mixure and coating the plugs, causing your ping.

Trust me, get the intake kit from your dealer, it comes with new bolts. You must use these new bolts, because they are stretch bolts made for only one use.

Flyinbrian

Also,
there is a TSB out on the ****ty factory plug wires Dodge uses, they need changed too. If you have not yet changed the factory wires, do this test. Open the hood in the dark while the motor is running and unplug the light under the hood for complete darkness. It should look like chinese fireworks from all of the spark jumping.

You still have an intake leak. Check your oil.

Here's a pic of my intake off my truck.

Flyinbrian

Ok, here's the pic~

Flyinbrian

Here is a pic of the underside of the intake.

Notice the gasket protruding, causing the vacuum leak and pinging.

Smitty

Mike,
You can test for a leak at the manifold.

Get a can of carb cleaner, start motor (helps if at operating temp) and spray carb clnr at/near any area all arond the manifold. You should not notice any change in idle speed. If you do respray the area to confirm that spot. If it changes then Brian is correct.

Good luck

Waterfoul

As I understand it a Service Bullitin is one step short of a re-call right? And the dealer is supposed to fix it at their cost if you have the issue? Well I'm over the mileage so will they pro-rate it or am I stuck with the whole bill? I REALLY DO NOT want to tear into my truck motor. I do it enough on my boat. I'm about worn out when it comes to motor repairs and such. I'm gonna try the carb cleaner spray thing though. I'll let you know what happens.

Flyinbrian, could you see the gasket protruding with the intake still installed on the motor? A friend at work had to replace his motor because his motor sucked the gasket into the motor, pretty much destroyed it. Did it at about 100,000 miles on his 98 360 motor. Now I'm scared!!!! Can't afford that. Hell, at the moment I can't even afford to fix it. Broke...broke...broke....

Ted G

Carb cleaner will not find the plenum plate leak. There is a way to do it though.

Disconnect the pcv valve from the valve cover and plug the hole.
Plug the intake air line on the other valve cover. Run the engine and check for vacuum at the oil fill cap. If the plenum plate is leaking it will cause vacuum in the engine-acting like a pcv valve. In some cases you can also see oil puddled in the area directly below the throttle plates. Take the air cleaner tube off the throttle body, hold open the throttle and look down there with a flashlight.

Ted G

Oh and BTW-the gasket will not kill the motor, but I have seen trucks where all the oil was sucked out and locked up the motor because they didn't check the oil level....so keep an eye on the oil level

Flyinbrian

THE CARB CLEANER TEST WILL NOT WORK IN THIS CASE!

The leak is on the bottom of the plenum, inside the lifter valley. The leak is not from the outside. Look again at the picture above. There is a plate that bolts to the bottom of the plenum, which is directly above the lifter valley.

TSB's are TSB's, from what I was told since I was out of warranty too, I could do it myself, or pay them to do it.

The same thing happened when the factory pinion gear went out. I had to do it myself.

Flyinbrian

insptech beat me to the punch. He is exactly right, pull the big goofy air cleaner box off the motor, open up the throttle plates, take a flashlight and look to the bottom for oil puddled.

Check the TSB website, it will run you through the pcv vacuum test step by step.