My exhaust :-(

The exhaust noise could be a joint or crack opening when under load. I have only come across this once (in twenty years) where inspection showed nothing, the noises got worse till the problem became obvious. Usually there are telltale signs of gas leakage, but not always.

mrcheerful

I had a BMW 525 ('92) which did this - I'd guess it was either an internal baffle rotting out or the sound absorbing wadding failing. There were no external holes other than the two at the end ;-) It lasted another few years before finally failing such that it had to be replaced.

I have a polo that does a similar thing when you take your foot off the accelerator. It makes a roaring, rattly noise. It is usually caused by the baffles being corroded. Banging the exhaust will show if the baffles are loose but not if they are just faulty but still attached. Unless you want the expense of replacing the exhaust you just have to live with it.

The tail end's still under garuntee, so it's a shame that it can't be proved. My car actually sounds like it's ages 5 years in the last few months, something's gotta be loose, it's a tiny noise at idle.

Ah, I've got some more news about the problem. After stopping in my driveway today it started 'spitting' again. I took a closer look this time, it was when I moved the gas pedal. I put my ear close to the exhaust pipe and when it was idling I could occassionally hear a spitting or a spluttering kind of noise. It was VERY faint when idling, but was just a quieter version of what I heard when moving the gas pedal.

I've checked my oil level, water level and my air filter and they all seem fine. Oh one other thing I noticed was a 'clonking' noise when pulling away, but this noise dissappeared about half way through the journey. Oh yeah, the spark plug gaps are 0.6mm (what the Lindsay Porter manual says) instead of 0.8mm (what the Haynes manual says), but that won't affect it will it?

SNIP

Have you checked the intake? With some engines if the hose from the air filter to the inlet manifold comes adrift it can make a roaring that sounds like exhaust from inside the vehicle.

Steve.

gaurantee. I'd just enjoy the extra noise if you're not getting pulled over.

Why don't you go to a Fiat dealer and ask them the plug gaps if the manuals aren't clear?

The message from "Doki" contains these words:

Guarantee

Doki ( snipped-for-privacy@spamtroNspidar.com) gurgled happily, sounding much like they were saying :

Or even guarantee...

OK, I've noticed a big difference in mpg when I change the gaps. I changed back to the 0.6mm gap when I put the last load of fuel in and then I filled up again today. During the last couple of weeks I have driven my car very hard, and even revved it at idle a bit to listen to the exhaust. I was expecting record fuel ecomonmy, but I somehow managed to get the best fuel economy I've had for a couple of months. My last few fill-ups gave me 33.3mpg (my lowest ever), 38.0 and 35.6. This time however I managed to get 40.2mpg. btw, I've had upto

I really couldn't understand this big hike, after I had driven it so hard. However believe it is the spark plug gaps that have caused it. This lot was all at 0.6mm, the previous one was 0.8mm and the one before was probably half and half.

As for performance, it's easy to demonstrate with a 50mph uphill road that I go on after work. With a 0.8mm gap, I need to floor it in 3rd and change into fourth at 50mph. I then give it lots of gas and try to keep it at 50mph until I get near the 40mph sign. With a 0.6mm gap I can change into fourth at 40mph and accelerate upto 50mph with about half throttle.

My observations are that the 0.8mm gap loves to be revved, but is gutless. The 0.6mm is noisier, doesn't like to be revved, seems to pink, but can usually run in a higher gear.

Of course, this last fill-up may have been due to the exhaust problem. I may have found another sympton today, my exhaust gases smell a bit like rotten eggs. Is this normal? It's not is it, doesn't it normally smell like petrol (btw it's a petrol not a diesel engine)? Could it be the cat (maybe I've got one stuck up a wheel arch ;-) ).

I checked a hose today, but not all of them. The roar is only really when I put my foot down, the main sympton now is a 'farting'/'spitting' noise from the exhaust. It happens slightly and faintly when idle, but it's louder/better with a bit of gas, but not much gas. If I use a lot of gas it won't fart. It farts both when the pedal goes down and when it comes up.

This is normal. My clio does this it is especially bad when you pull up and get out after a hard journey. Also if the spitting spluttering noise is the same as what I think my car does it too but mine does it more at idle than at a bit of throttle. It almost sounds like the engine is going to stall for half a second then the ECU puts more fuel in to stop it stalling or something like that. My car is less than 2 years old and its done it since new.

Hope this helps Richard

It's not is it, doesn't it

I'm not sure whether we've got the same problem. Anyway, my car never used to do what it's doing now, and it's becoming more frequent.

Oh, I know what you mean! My one does that too, but it's normal. Just a slightly rough idle. The revs just drop occasionally for a moment. That's not my problem. When my exhaust 'farts' the exhaust actually vibrates.

OK, I've descovered something new. The 'farting' doesn't happen when the engine's cold (ie. within a mile of driving). After about 1.5 miles it does happen though. I believe the reason for this is because the engine is less responsive when cold. What I mean is if you take the foot of the gas pedal there is usually a lag before the revvs gradually start to fall.

I'm guessing that this will mean that the change in pressure will not be as great. Does this still sound a lot like an exhaust, or could something else be causing it? I'm getting a bit worried, my uncle covered up the zorst today and it didn't seem to be leaking :-(

As I've said before though, my cylinder head gasket may be leaking, can this cause this sympton? btw, my oil and coolant levels were good a few days ago.

As Dave said, possibly collapsing exhaust baffles. Especially relevant in your case, as it could also account for the power loss you've been describing recently.

Stuart Sharp

OK, my dad reckons it's the cylinder head gasket :-(

The problem doesn't happen when the engine's cold, probably due to something opening up. What do you guys think?

To be perfectly frank:

Just take the bl00dy thing to a garage. Either get them to fix it or part exchange it!

The pinking's probably burned a valve seat or 8 out, or something.

One thing I did think about - has the fanbelt (or aux belt) been changed? On the 899 engine (903cc derivative), the crank position system is a toothed wheel on the end of the crank pulley. To change the belt, you've got to loosen the TDC hall sensor. If it's been removed "the wrong way", (I.e. by undoing one set of bolts rather than the other), the timing could be out.

Pete.