On me old Fiesta, it sounds like the exhaust blows when it's started in
the Winter. At least, I think it's the exhaust. It makes an almost
tinny, squeaky sound, when under load at very low revs (like rolling off
in second when you should really be in first), and then it's okay when
it's warmed up. Each year, I say I'll fix it when it's warmer, but I
always forget. And it won't do it neutral, so it doesn't help to get
the missus to rev it while I listen from the outside.
I was wondering if there's anything else it could be? Is it a common
Actually, I think it does pink at other times, too. There is a rattling
noise when accelerating before it's properly warmed up. I wonder if
this is another specific symptom that only happens in Winter?
Trouble is, I see no way to change the timing, because AFAIK the ECU
takes care of all that. I've wondered if the knock sensor is broken,
although I get no management light or fault codes. I also wondered if
one or both of the oxygen sensors needed replacing, although again - no
codes, and I get good readings at MOT time.
Usual way to check for an exhaust leak is to block off the tailpipe with
your hand. Cover it with a bit of rag if you don't like getting dirty. A
leak can then be more easily heard; if it's not leaking, it should almost
stall before it pushes your hand away.
I can think of no reason why an exhaust would only leak in the winter, and
wonder if it had a leak that could be heard when driving, how it passes
Okay, I'll see if I can make it more audible by doing something like that.
Well, I was thinking maybe the metal was contracting (due to the cold)
just enough to make it leak until it had warmed up. Or maybe the choke
(assuming the ECU does something about the mixture when it's very cold)
was somehow creating denser exhaust gases for a few minutes.
The MOT place I take it to (a local ATS, who just keep passing it every
year for £30) also does exhausts, so I assume they'd be looking for a
sales opportunity. They never mention it.
I've sometimes wondered if the pinking noise I sometimes hear is the
cat's insides rattling around. I've tried thumping it, but it sounds
solid. I wonder if I can get my borescope in the oxygen sensor hole?
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