And still there's a rattle

The message from Simon Dean contains these words:

Sounds like they changed the convertor for nothing then.

Commonest reason for that sort of rattle is a loose heat-shield. The other thing that might sound like a rattle is possible pinking. Would you recognise the sound of an engine pinking of that's what it were?

I know. That's my biggest fear at the moment. £200 wasted. Still the heat shields were loose on that before, and there was quite a bit of noise - though its hard to think what. I've forgotten the previous noises. Anyhow, Im just tricking myself into believing that the new cat has made some improvement in responsiveness, smooth running, less noise and better economy. And true, the fuel economy is *marginally* better.

Head shield eh? Maybe related therefore, first time I start the car up,for about 10 minutes, there a certain vibration at a certain rpm and under load.

As for pinking, I dont know. I have absolutely no idea. Its pre-ignition right? Detonation? The most I've read so far is that I'd notice it for sure, its unmistakable. And so far the noise, annoying though it might be, doesn't sound like its eminating from the engine. Its not that loud.

But still I dont know. No one's ever said to me "There - that's the sound pinking makes".

Cheers Simon

Oh yeah, just to give you some figures. Before cat: 5.3 miles a litre. First fill up after cat, 5.5 miles a litre. Economy wise, its still also a little better now. met get 5.7 miles a litre at next fill up :-)

Cheers Simon

Not if it was knackered. Would almost certainly have failed on emissions at the next MOT. So would have had to be replaced then anyway.

Still the

bit of

previous

the new cat

less noise

better.

heat-shield. The

pinking. Would

it were?

the car

certain rpm and

pre-ignition

notice it for

it might

that loud.

Pinking is often not that loud. Quite noticeable though, and is usually directly related to a higher load on the engine. Recognised as a high pitched regular tinkle when the accelerator pedal is depressed. Mike.

Yes and no.

These are the MOT results so far:

2001 Fast Idle: 0.00% vol CO, 4 ppm vol HC, 1.030 Lambda 2001 Slow Idle: 0.00% vol CO 2002 Fast Idle: 0.00% vol CO, 0 ppm vol HC, 1.008 Lambda 2002 Slow Idle: Not Done 2003 Fast Idle: 0.01% vol CO, 16ppm vol HC, 1.011 Lambda 2003 Slow Idle: 0.01% vol CO

So of course then, big question, what does that indicate? Not a lot Im guessing. Bigger question is, was the cat really knackered in the first place. I have however noticed fewer, if not no eggy smells from my cat anymore.

Hrm.

Ok, I get a tinkle if I suddenly I accelerate, and at a specific load, such as cruising along a motorway. If I heavily accelerate, the tinkling goes away. Ok, maybe that should be less noticable. But I dont notice it.

Pushing on the accelerator at stand still gives the briefest of tinkles.

So if it is preignition, what's causing it? I first really noticed it after I got the front part of the exhaust changed. I was also notified by Nissan that my O2 sensor was "failing", so I replaced that with a genuine replacement. Still notice this ticking, get a new cat. Still notice the ticking.

I refuse to believe its running to lean, I'm only getting on average,

5.5 miles a litre. Too hot? The temperature needle on the dash is just under half way. Everything else, timing, mixture etc should be computer controlled right? Genuine Nissan Spark Plugs, Leads, Distributor, Cap etc... all changed about 4 months ago.

The noise definately sounds like its coming from underneath the car somewhere. Though that could just be trick of the ear???

Cheers Simon

is that

noise,

eminating from

and is

Recognised

is

specific load,

the tinkling

notice it.

Whatever is causing that noise, it definitely doesn't sound like pinking to me. If it were. The noise, pinking, would continue as long as you were accelerating. Pinking is more relevant to the load on the engine, rather than the revs.

of tinkles.

Nope. That sounds more like something that rattles at a specific frequency.

If it does it while it's stationary, I'd suggest looking for it under the car, with the car on axle stands or on a hydraulic lift. Just keep prodding at suspects with a screwdriver or a thinnish rod while someone inside the car tries to hold the revs at the right place until you find it. There is also the possibility, that one of the exhaust boxes has a loose baffle.

I don't think it is preignition. Sounds more like the rattle is caused by a loose part, or two parts that can just touch at a certain frequency. Mike.

Excellent news. Thanks for that. Though I am cautious about what I write. I dont hear said tinkles at a higher engine load for example, but that doesn't necessarily mean they aren't there, just that, I dont notice them.

I'll get the exhaust guy to reinspect.

Cheers Simon

Just so my minds clear...

The noise happens under the following scenarios:

• At Stand Still - Sharply accelerating for a second or so

• Any form of extra acceleration, light to medium acceleration/engine load only will show this noise.

The noise doesn't show under heavy acceleration/engine load or sustained acceleration at standstill in neutral

Though it is there if I push on the brake pedal, and try accelerating in gear (Drive, or reverse (in fact most noticable in reverse I think)... upto about 1500 rpm (this is an automatic), so there is a medium load on the engine.

Dont hold me to that last paragraph. Im at work at the mo, and Im 80% sure I can recall hearing the noise in gear like this. Though itcould all be other rattles Im mishearing. I have a habit of that.

Cheers Simon

25Mpg doesn't sound very good economy for a 2 litre petrol automatic.

You should be getting better unless you spend your whole driving life in traffic.

-- James

like

continue as long

load on

what I

example, but

dont

Unless you're hard of hearing, I think you would notice pinking. Even if the car is particularly noisy, the chances are that you'd hear it over any wind, road noise or bodywork rattles. Mike.

So what do you think would cause a noise like this...

Mondeo 1998 2 litre petrol.

At between 2000 and 2750 rpm, in 3rd gear or higher, with full throttle, but where the full throttle wouldn't really "work" (I.e. up a slight incline in a high gear, medium throttle will keep the car steady, but the revs are too low that full throttle won't accelerate hard), there's a "hushing" or "Shush" noise from the engine or gearbox.

I'm pretty sure it's not pinking, it's not a harsh diesel sound, just a "hush" noise. (Sort of the "ch" in loch, repeated over and over).

Letting off the throttle will stop the noise

The only thing I can think is that it's just gearbox noise, or just the sound of exhaust gas or something like that.

Pete.

snipped-for-privacy@clara.co.uk

like

you

than

throttle,

slight

steady, but the

there's a

Might be pinking. It's the right circumstances, but as I mentioned earlier, pinking is normally quite high pitched. IME similar to the sound made by tapping a wine glass with a spoon. I can't imagine anyone describing it a 'shushing' noise.

just the

Could be a blowing exhaust, but it's difficult to guess without actually hearing it. A small blow can often only be heard clearly under certain circumstances, and can sound like your description, but be unnoticed when running normally. I think you can safely rule out the g/box as the source. Mike.

I know the sound of pinking from my previous cars, and it sounds like a cold diesel engine, and it's certainly not that noise. It's not even very quick, or lots of pinking, just a hushing noise.

It's been doing it for just under 100,000 miles, so I'm assuming it's nothing too serious :-)

Pete.