Alan A

So when I press the loud pedal I hear a rattle for a couple of seconds while the revs build. It's consistently coming from the passenger side rear, and it either stops or I'm busy concentrating on hanging onto the wheel in short order.

It's bloody annoying.

Anyone care to hazard a guess where to start looking for the source? Please don't be a smartass. I already know it's in the engine bay...

Car passed a PPI and was just serviced by a good indie. Neither noticed anything badly amiss.

Delicious

Hi,

I am no expert in the Porsche world, but have a long background in engine management tuning. Has the vehicle's ECU been tuned or is it stock and how long has this been going on?

Atrox

Heat shield, cats, exhaust... Start tapping around see if anything is loosey goosey

Carlo_Carrera

Turbo heat shield is loose or cracked. It is very common for the bolts that secure them to loosen up over time and/or the shields themselves to crack.

fpb111

What Gear? What speed? What RPM?

Alan A

Second or third. 2500-4000 or so, right where the power starts to come in (it has a umw flash).

Sounds like I need to get my *** underneath it and look for loose stuff.
Hopefully it's something trivial. Sounds like it at least.

Kevin

Is it present with the stock file loaded in the ECU?

Have you changed your plugs recently?

993GT

only at WOT, preboost? perhaps, wastegates actuators or shaft/valves very loose/broken

Carlo_Carrera

It is a heat shield. Get under the car with a rubber mallet and start tapping around. You will find it.

Alan A

Plugs were done by PO based on P service schedule. I'd have to go through the documentation to find out when that was.

I'll check with the stock tune when I get home in daylight and it stops raining.
I don't think it's anything to do with the tune though - it sounds like something is loose.

Not only at WOT. 50% will do the trick.

==

If I wasn't so busy I'd jack the thing up and poke around. I'm hopeful it's something silly like a loose heatshield. I just wanted a starting point to narrow it down.

I've had plenty of practice taking old cars to pieces (I've even managed to get one or two back together) - but this one is built to a different level of complexity to the ones I'm used to and I'm leery of making an expensive mistake if I just start dismantling or whaling on stuff.

dprantl

Can you hear the sound when the car is stopped, in neutral and you have the clutch pressed?

Dan

Alan A

No. Not to be (too much) of an ***, but that would be a "rattle when stationary with the clutch pressed" rather than a "rattle on acceleration".

I have a place to start - consensus is a loose bolt on something or other, so I'll go look at that first.

Thanks all.

993GT

does the car have to be under load? IE. if you free rev it while the car is still, does it make the noise, or does it require load/accel?

Alan A

So that was ... inconclusive.

Looked underneath it. Everything is firmly attached. Nothing is broken. One of the brackets on the drivers turbo is starting to rust, but that's a separate issue.

Revved it stationary - no noise.
Revved stationary with the clutch depressed - no noise so I don't think it's a TOB - plus this noise is more box of rocks rattle than the sort of metallic ticking I'd expect to hear on any other car.

The one thing that's noticeably different is the rear wheel splashshield side:side.

For reference its the one at the back of the rear fender well that comes back and covers a soft black air hose out of (likely) the turbo - I wasn't under far enough to see if it's the pressurized one or not and I'm not familiar enough with this engine to know.

The replaced one is made from a much harder plastic material whereas the original one is closer to a rubber material.
I can tap it, have it hit that black air hose and have it make a noise. The rubber one is much much quieter when I do the same. I'm wondering if that's what it is - it's hitting the pipe under load. It's the only thing I can see that's free to move that will make any noise when I tap on it. That said, this replacement is supposed to be OE and while I didn't have a lot of miles on it, I don't remember hearing this before it came back from the shop.

But then I also added the flash at the same time so I can't conclusively say that's what it is either.

Edit - I grabbed this picture off the interwebz so you can see the piece I'm talking about. This isn't my car.




I may try a piece of window seal between the two before I go out next time and see if that fixes it. If not I'm stumped for now. The weather is too crappy to take it out and to eliminate the tune as a variable.
But then I don't think that's what it is. I shouldn't have done two things at the same time - that'll teach me.

Atrox

Maybe honeycomb in cat?

Saw that picture and was like damn that exhaust is new, and bad **** how could the exhaust be making issues.

Or you could just be paranoid as these cars tend always have an elusive rattle.

I had put a cd in my door pocket driver side that I forgot about , and it would thump the inside. I was always searching for the sound until I needed to put the cd back in the case.