I have a 99 Ram 1500 with the 5.9L magnum. After it gets warmed up it runs fine until i get up to 45 mph then i hear nosie that sounds like the lifters until about 55 mph. The rpms are usually around 2500 to 3000 approx, and it only happen when i'm getting on the gas. It doesn't matter if i'm climbing a hill or on flat land. I have tried changing fuel brand, octane, plug wires, plug heat range, fuel treatment, and fuel system cleaner that suppose to clean injectors and carbon build up from valves. But still no luck. Anyone have any ideas to help cure this problem.

 

Have you replaced your Plenum yet?

https://dodgeforum.com/forum/2nd-gen...um-thread.html

 

welcome to df. do you think its a mechanical clicking/banging or could it be pinging (spark knock)? doies it sound like a rattling sound, and is it heavier when the press the gas pedal and lesser when if you ease up on the pedal.

spark knock and pinging is usually lessened or eliminated by high octane gas.

if you think it might be pinging, search on "plenum" for about a million posts. its a very common problem in our trucks and the intake leak usually causes mild to severe pinging.

edit... i'm too slow.

 

It does sound like pinging, and not lifters.

From TSB 09-05-00, testing for blown plenum gasket:

Symptom/Condition:
An engine intake manifold plenum pan gasket oil leak may occur on some V-6 and V-8 style engines. The oil leak is internal to the engine so no external oil leakage will be present. Two symptoms of this oil leak condition may be present. The vehicle operator may experience an engine spark knock during acceleration and/or an increase in the amount of engine oil consumed by the engine.

http://dodgeram.info/tsb/2000/09-05-00.htm

That TSB has a procedure for checking for engine vacuum inside the crankcase that would indicate a blown plenum gasket. I wouldn't be surprised if you do have vacuum, and also the tell-tale pooling of oil on the plenum plate on the bottom of the intake manifold. Just take off your air cleaner, open up the throttle plate, and have a look inside.

As for octane, your engine was designed to run on 87/"low test", and if you get pinging on that grade, there's probably something wrong with it.

I think a lot of people (not saying you're one of them) think that a healthy engine that doesn't ping on 87 octane will somehow go like a bat out of hell on 93, when it's the exact opposite. These same people don't seem to understand that higher octane gasoline just burns more slowly, to avoid pinging in higher-compression engines. [Gets down from soap box].

 

stewie01
I have not replaced your Plenum yet. What is the plenum?

 

It's the bottom plate of the intake manifold. Over time the plate warps from heat and the gasket fails.

You should check out the link in my first reply, it'll explain everything in great detail. One of the side effects to a blown Plenum is your engine will sometimes sound like a can of marbles and seem like it has no power.

There are the Hughes Plenum kits http://www.hughesengines.com/Index/p...z&partid=26190

You can get some cheaper on ebay.

That's where I would start if it hasn't already been replaced.

 

dhvaughan
I have tried changing fuel brand, and octane.
It could be pinging ( spark knock ). It does sound like a rattling, but it doesn't really get heavier or less when i press the gas pedal. The noise happens in a specific range, and only when warmed up after about 30 minutes of running. There really isn't any change in the tone of the noise.

 

stewie01
I dont know if it has ever been replaced. I bought it about 6yrs ago, and it only has about 84k miles on it now. I will check out the links you've supplied.

 

stewie01
After looking at the first link you sent i'm thinking it might be the plenum. Oil consumption, knock under load, #8 spark plug fouling, and gas milage are all issues that i'm seeing in my truck. This being the case does it mean plenum has to be replaced or just the gasket? Sence i have owned it the truck has never over heated, I dont know ever did before i got it of coarse. btw i dont have any power issues.

 

There are a few of ways to check. You can take off your breather box and open your butterflies (flashlight may be needed to see down in there) and see if you see oil down in the intake, if so your plenum is blown.