2000 Boxster - Cold start noises

Hello, first time poster here.

I have a 2000 Boxster 3.2 with 5 speed.

It's 100% stock and has 140,000 km on it.

It has a weird phenomenon on cold start.... it runs rough and makes a random cracking/knocking sound which sounds like a small stone in the clutch area.

I narrowed this noise down to backfires in the exhaust.

It does this for about 30 seconds then everything just smooths right out.

Only on cold start.

The AOS was recently replaced and my first hunch was a vacuum leak but I cannot find any.

Any suggestions ?

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Dohc Rocks
Hello, first time poster here.

I have a 2000 Boxster 3.2 with 5 speed.

It's 100% stock and has 140,000 km on it.

It has a weird phenomenon on cold start.... it runs rough and makes a random cracking/knocking sound which sounds like a small stone in the clutch area.

I narrowed this noise down to backfires in the exhaust.

It does this for about 30 seconds then everything just smooths right out.

Only on cold start.

The AOS was recently replaced and my first hunch was a vacuum leak but I cannot find any.

Any suggestions ?

3.2l with a 5-speed? Are you sure?

Is the car new to you or have you owned it a while and this just started out of the blue?

Without knowing the history of the car there is the question about the plugs, coils, engine air filter, fuel filter, and gasoline condition. There is also the possibility of one or more injectors leaking. They could just be dirty to.

If the car is new to you, a treatment of Techron could be called for. This will clean the fuel system, remove deposits from the injector tips (and other places) and can improve the engine's behavior.

Backfires in the exhaust is a sign the engine is running rich. The DME does this on purpose at cold start to supply extra fuel to the converters where it is burned to accelerate warmup of the converters. This extra fuel is supplied air to burn with by the secondary air injection pump.

The extra fuel tends to make the engine sound a bit ragged, run a bit rough.

To the uninitiated, to those new to the Porsche world, this rougher running can be a bit disconcerting.

Is the CEL on?

If the CEL is not on and there are no pending codes, it could be the behavior is normal. Has it turned off colder where you are?

I don't want to downplay this too much, because without a video/audio clip of the behavior it is impossible to know if the behavior is normal or abnormal.

Unless you are prepared to get ahold of say an OBD2 code reader/data viewer and get your hands dirty, my advice would be to let a pro Porsche tech give a listen and advise you.

While my 2000 S didn't make those noises, but it did require a real thorough cleaning of the throttle body. It would run really rough at idle and the rpms would bob...... something to check out. Good luck.


Peace
Bruce in Philly