Rattling on acceleration
 

Almost every time, if I accelerate hard to very hard, there is a rattling sound coming from the front, like screws in a glass jar. Belts & pulleys/tensioners were replaced and that made no difference.

What grade of fuel are you using?

Years ago I had a catalytic converter heat shield do that. Is that possible?

93 octane Shell

I know there's some difference between the way the US & UK determine petrol grade, but the minimum spec in the UK is 95RON. I'm thinking you're hearing engine knock, if you can get higher grade fuel in your area I'd try a tankful, it can't do any harm, unless you've been running this grade for years without trouble.

The OP is in spec. No need to guess:

Octane rating - Wikipedia, the free encyclopedia

Could it be the supercharger?

Here is some old info for your car.

bob gauff

Hi Bob

Thanks for the info. It only occurs on heavy throttle and at low speeds too, 20-30 mph. I have always used Shell 93 octane. No chance it is the supercharger?

I assume this is the same car you've been chasing the other noise?? Is this a new description or a different 'noise'??

I'm still waiting for a resolution on the other thread...... I'm hooked.

Cheers,

No resolution to the other issue and I do not believe they are related. I have not had time to take the car to the shop again, perhaps towards the end of next week.

Well then, the things that come to mind are:

The attached Bulletin regarding detonation on your Super; if it's never been done.
Thermostat allowing an elevated engine temp, maybe not an actual over-heat.
Make sure the induction intercooler pump is operating.
Possible injector buildup reducing fuel. Could try a couple of tanks with BG 44K fuel cleaner added a couple of weeks apart.

I wouldn't say it COULDN'T be the supercharger, but I doubt it.

Cheers,

Put in a can of 44k and the rattle appears to have gone away, acceleration seems smoother too. Don't think the bottle of Techron I used a few months back did anything like the BG. I'll continue to observe and report if anything changes.

Thanks for the help, everyone!

Cool, thanks for reporting back! We like feedback. As more and more results come in I'm more inclined to suggest using the 44k on a somewhat regular basis; it seems to live up to the claims, time and again.

Cheers,

Rattle went away after 1st can, came back after 2nd fill up, went away with 2nd can and has not returned after about 4 fill up since.

I appreciate your attention to detail and reporting the results. I can't tell you how hard it is to really quantify the benefit of this cleaner. I rarely get the kind of confirmation I need to properly assess the results. I usually have to interpolate based on whether an owner returns with further complaints or not. If they don't come back, I have to guess; did it fix the issue, or did they throw their hands up and decide I was a quack that didn't know what I was doing??

I'll surely be interested in how long term the improvement is with your car.

How does it feel to be the engineering department?? :icon_crackup:

Cheers,

I am an engineer, actually, in electronics (automation, robotics, video & acoustics). Perhaps that will explain a bit about my posts on this forum.

Unfortunately there is no quantifiable data here particularly due to also have the injectors cleaned at the same time and that will, like other things with this car leave me guessing as to what the solution was.

What we do have is coincidence and a problem solved which should satisfy my concern. FWIW though I did put a couple of cans in each of my other cars even though they exhibited no signs of needing it.

This car has become somewhat of a hobby I suppose and have been pleased with the accessibility of service manuals (and this forum). I have been very involved with every car I have owned while at the same time letting the dealers worry about most of the maintenance as needed until time to trade up to the newest model prior to warranty expiry. But as mentioned several times before, there is something special about this one and will keep it in like new condition for as long as I am able even if it (and my favourite Jag dealer) frustrates me from time to time. :D

WOW! My crystal ball was workin' that day, whatnit?? :icon_woot:

Don't be so quick to write off the value of your reporting on the use of BG44K. Every little bit of information helps. As I said somewhere here before, I am becoming a believer more and more as time goes on. And that's coming from a guy that used to be one of those that always recommended AGAINST most any additive. I NEVER had my life made easier by anything added to any automotive tank, fluid or oil.......until now. This seems to be a direct result of fuel quality and newer multi-point, fine spray injectors.

Still collecting data........appreciate the input!

Wow, "snake oil" that really works. I am tempted to buy a can to use preventatively, based on this thread.

Where to buy at retail? I have so far not found it in the major auto parts chains.