Intermittent rattle/clatter when accelerating

[mlnnc]

I've been a pretty regular reader and sometimes contributor to this and other LR forums for 3 1/2 years or so now but I don't recall ever seeing this discussed or diagnosed.

Starting just a couple of days ago I intermittently hear a clatter or rattle when accelerating with the engine at operating temperature. When I say intermittent I mean that in traffic around town or on a highway if I accelerate a dozen times I hear it probably 3-4 times.

I call it a rattle or a clatter because it is definitely lower pitched than the "tick" these engines are known to make from time to time (including mine).

The engine has 135,000 miles on it. As my signature shows I replaced the headgaskets myself at 109,000, three years ago last week. It's throwing no codes and drives nicely. But the rattle/clatter has me concerned. Might it be a worn cam? The bottom end of these engines seem to be a problem only rarely, plus I recall reading somewhere else years ago that rod or crank bearing problems produce a knock when decelerating, not accelerating.

Any ideas? Thanks.

 

[riceybean]

Flex plate, heat shield, cats?

 

[mike97d1]

Could it be spark knock?
What's the temp outside? Temp of engine? Is it only under load, or does it do it at a cruising speed too? Have you put anything in the fuel to clean the injectors or combustion chambers lately? What octane do you run?

 

[mlnnc]

It's not a spark knock; I know what that sounds like. I said it happens at operating temp, which for this truck is 194-198 degrees Fahrenheit. Ambient temp was around 80 degrees. It happens only under load (accelerating). I run premium fuel only. Combustion chambers were cleaned thoroughly when the headgaskets were replaced 26,000 miles/3 years ago. Again, it's not preignition. And it's too clearly rhythmic and tied to engine speed to be something like cats or a loose heat shield, I think. (Flex plate?)

 

[jymmiejamz]

I've seen a couple of broken flex plates, but its not very common.

 

[messar]

bad water pump? drive shaft?

 

[antichrist]

If it sounds like several (or more) ball bearings rattling in a metal tube it's probably the catalyst breaking up and rattling. With your mileage that's a good candidate. My '95 started doing it around then. I drove it like that for about another 100,000 miles. I think it finally all broke up and quit rattling.

 

[crown14]

Sounds like cats. Do you ever hear it at idle?

 

[jastutte]

following this with some interest. have the same issue, the rattle at acceleration, on my 96 discovery. 189,000 miles and original cats. no codes, so hoping it's the cats.

 

[hk9176251]

Mine had a heat shield right above the front drive shaft that was hangjng and doing something similar taping on the drive
Shaft during acceleration the passenger in the truck could feel it on their feet through the floor

 

[Bosbefok]

The heat shield on my driver's side cat cracked a weld and it would rattle under acceleration at certain RPMs only.

 

[pathas]

catalytic converter - the thing I don't like about this forum is that people start a thread to ask a question and then never post the resolution. frustrating.

 

[mlnnc]

catalytic converter - the thing I don't like about this forum is that people start a thread to ask a question and then never post the resolution. frustrating.

I didn't post the resolution three years ago because I didn't have the resolution until just a few weeks ago.

The noise got progressively worse over time, but the truck wasn't being driven a lot so I didn't obsess about it. Turned out to be a failure of the exhaust manifold to downpipe gasket on the passenger side of the truck. After a $9 gasket, some PB Blaster and 30 minutes of work the noise was gone.