535 stumbling when cold + muffler needed

[Kamil]

So, with almost 240k on the odo, the car is doing very well, besides needing a muffler.
Recently I've noticed, that when started and driven right away (engine cold, (unrelated to ambient temp)), the car feels like it has very little power.
It's sort of stumbing, dosen't really want to move. It idles fine, any idea what it could be? It burns just about no oil and once warmed up, it drives great, with plenty of power... and some drivetrain noises that I have to look into. :)

Any idea why the lack of power when cold? Idle control valave?

New plugs (8k miles), new fuel filter (4k miles), might need cap/rotor/cables and air filter, tho this might be/probably is unrelated.

Also, where's a good place to get a replacement muffler? Maybe something meaner sounding? ;)

[Robin-535im]

No expert advice here but a shot from the hip:

The DME tweaks the fuel trim based on the inlet air and head temperatures. If one of the temp sensors is bad, it could cause cold-running instability that could go away at operating temp when the fuel trim is adjusted with the O2 signal. I think Bently has a procedure for checking them.

It sounds to me like the open-loop mode (i.e., when the engine is cold and not setting the fuel trim per the O2 sensor signal) is running at a bad mixture (too rich or too lean).

HTH

Robin