strange sound on start-up

[Matt X2C]

for the past few weeks my car seems to sound very strange either the first time i start it, or after it is left for hours and hours...basically when it is stone cold.

not sure whether it is down to the engine, aftermarket exhaust, or lamba sensor not being put back in yet (but it has been happening since not long after this was removed) but it is noticeable.

the car basically sounds a bit tinny, and like its got anti-lag (basically bwarp bwarb bwarb bward very quickly, but without the pops and bangs lol)

anyone know what it could be??

i have a feeling that it could be down to the exhaust...if you put your foot down a fair bit before it has fully warmed up the exhaust gives off a bad note, a resonating high pitched one rather than normal.

Could it be down to the exhaust moving/shrinking etc as it goes from cold to hot? because as I say when the car is upto temperature it sounds proper on the money.

its not shockingly bad, but its noticeable.

any ideas?

 

[artdealer]

Maybe Yozzasport boys could give you an opinion as they have more experience of the effects different mods have.

bwarp bwarb bwarb bward - you have opened yourself up with this description, that could be anything from engine, to exhaust to Eurovision

 

[Steve]

My money's on the lack of oxygen sensor.

 

[Matt X2C]

it was actually 10 times better this morning...maybe because it was so hot.

Im gonna try my best to get the lamba sensor in on thurs and then see the difference. But as I say, as soon as its warm its absolutely fine!

 

[Cue]

i was getting a sound that sounded a bit like a knitting machine under the engine - hasn't done it since the weather has improved though, it got quite loud over jan/feb - steelers couldn't identify it :?

 

[7MAT]

My car sometimes pops and bangs from cold, in fact it did it this morning.

 

[Matt X2C]

My car sometimes pops and bangs from cold, in fact it did it this morning.

mine does that, if you rev it a bit, and just jab the throttle it goes 'pop' :lol:

 

[Steve]

This is all part of the start-up mode, the fuelling and valve overlap is all different for the first 75 seconds to allow for the Cat to warm up so the car could pass emissions, a cold cat doesn't do anything. This is why performance is also severely limited, it shouldn't be an issue because if you're using full throttle load in the first 75 seconds, you're going to start hearing lots more noises once your engine is fooked.

 

[Matt X2C]

This is all part of the start-up mode, the fuelling and valve overlap is all different for the first 75 seconds to allow for the Cat to warm up so the car could pass emissions, a cold cat doesn't do anything. This is why performance is also severely limited, it shouldn't be an issue because if you're using full throttle load in the first 75 seconds, you're going to start hearing lots more noises once your engine is fooked.

im not using anywhere near full throttle. I don't go over 3k and only use the accelerator softly for at least 5 minutes. you can hear the difference at idol!

 

[TrophyK3V]

Think they all run really rough on first start up