I have a clattering sound sometimes when I accelerate.
It’s always when I’m driving at a steady slow speed, maybe 30 mph. The transmission is in maybe 4th or 5th gear.
I press the accelerator to speed up and I hear a clattering noise, like valve clatter. I only use the highest octane fuel. Any ideas?

 

Does it happen all the time ? Or only when the engine is cold ?

My car has noticeable piston slap when the engine is cold. I’ve read on the forum that piston slap noise is typical on these engines when cold or cool.

it may be a waste of gas, but I like letting the engine get to at least 160 F / 71 C before driving off. No clatter then.

if your car is making a knocking noise at all temperatures, then it’s likely another issue, and not normal. In that case more investigation is called for before it gets worse, ie expensive.

Z

 

If its a clatter like loose exhaust baffles then you are low on auto transmission fluid. Mine drained 3.6 litres but took 6.5 to fill it.
Piston slap which comes and goes from day to day sounds like an excessive tappet gap and shows up at idle

 

It isn’t low on transmission fluid. I just changed the fluid and filter.
I had the noise before and after. It’s coming from the engine, on the left side. It doesn’t happen at idle, although there is a slight ticking sound at idle.
It happens, as I said in my post, when I am driving along at a steady speed and I accelerate, causing a downshift.
It sounds exactly like valve clatter.
It only lasts for a couple of seconds. If I am shifting manually, say in 2nd, then 3rd, and I’m at a steady speed, then I accelerate, it doesn’t make the noise. It’s only when the engine is at a low (under 2K rpm) speed and then I suddenly accelerate, to get around a slower vehicle, that I hear it.

Is there a variable valve solenoid or something that controls the timing? Perhaps that is going bad?

 

Jaguar addressed this issue decades ago.

 

My VIN is 37254. It falls outside the range of the TSB, by over 100 cars. You would think it was fixed by then.

 

Loose catalyst?

 

No. The entire exhaust is secure.
It’s valve clatter. I know the sound.
It’s like when your timing is off on your old 350 V8.
Or, when I used to have a Mercedes Benz with the 3 liter inline six. If I used low octane fuel, the valves clattered under acceleration.

 

With all due respect, the noise from using low octane fuel or too advanced timing is called “pinging” and has nothing to do with the valve train.

A pinging or “rattling” sound is from detonation. If left unchecked it will be like a hammer hitting the piston crown over and over.

I have no idea what you are hearing, I did like the post that suggested the loose catalyst. Which I took to mean an internal loose component, not externally loose on a hanger or bracket.

Best of luck in resolving the issue.

Z

 

Check the transmission fluid level