Would a bad muffler cause rough acceleration?

[jnorion]

I'm looking at buying a new Legacy, and when I took it for a test drive I noticed there was a lot of hesitation and rough acceleration. There didn't seem to be any loss of overall power, the car was quick enough, it was just uneven power. Also, there was a CEL on most of the time.

The muffler is rusted out and destroyed to the point where it sounds like there isn't one. The previous owner was trying to tell me that the muffler was the main problem, but that didn't sound right to me. Could that be enough to cause that issue or should I be looking for something more?

[Saskatoon Subaru]

my 90 legacy has a horrible exhaust system (pipes comeing down from engine are cracked, 1 huge hole in muffler and a few small ones) and my cars acceleration is smooth, reallllyyyyy loud, but smooth.

[jnorion]

I was afraid of that.

[rallysam]

Yeah, the car wouldn't really know whether the muffler was there or not - it wouldn't drive very differently and it also wouldn't throw CELs.

Vikash used to disconnect the whole exhaust system after the downpipe when he was drag racing, and the car ran fine. Presumably slightly faster, but otherwise the same - no problems.

So, the car you're looking at probably has one of a million other little sensor failures or electronic quirks that these old cars get all the time.

If you pull the CEL code, you'll be about halfway to figuring out what the problem is. I've crawled under the dash even on other people's Legacies that I was test driving.

[jamal]

pulling the code is easy enough. My bet is the knock sensor ($48)

[jnorion]

Yeah, I'm not terribly worried, the car only cost me $500 and it runs fine as it is. I noticed yesterday that it gets smoother as it warms up. Today or tomorrow I'm going to get the code to see what's going on.