Noise at 2500-3000 revs

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nobbya

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My Audi 80 sport has developed a noise. The noise is a low pitch vibratory pulse which occurs under acceleration between 2500 and 3000 rpm. The noise also increases in frequency through this rpm range.

The noise is not present when the car is out of gear and then throttle applied to the relevant rpm, and also does not occur when the car is first started (it takes till at lease 60 degrees c on the temp gauge to occur).

I am toying with the idea that it's a gearbox problem but the noise sounds suspiciously like a bearing.
 
Not speed related as it happens whichever gear I am in at those revs. I tryed it out last night on a stretch of road nearby which has just been resufaced with a noiselesss surface and when the car is cold there is definately nothing.

When the car is warmed up though it occurs and appears to be more pronounced when I accelerate hard.
 
sounds like a bearing problem? hard to tell without listening to the noise. find a decent engine rebuild company near you and aks them if they will take a listen.
knocking under load can be main end bearings.

It could also be pinking (pre-ignition)? especially while under load. since it only happens when warm it could be that the fuel/air ratios are correct when cold, but change when the car warms up and so causing pinking.

another cause could be from one of the various pumps, eg a water pump. when the car is cold there is clearance but not when warm, etc.

I doubt it is piston slap, normally only happens when cold. also doubt big-ends, as this is normally quieter under load.

what millage has the engine done?
 
The car has just passed 69000 miles.

It's funny now that you mention it but the noise is not a loud noise and I only noticed it because I am so used with the normal car sound.

What exactly is pinking?

I have another problem where I have been told by a friend that this is pre-ignition. When I start the car in cold weather a ticking sound continues after ignition and takes about a second or so after the engine start to die off.

Could they be related? and how would that be sorted out?

If it is main end bearings what is the procedure for recifying this and is it bad to continue running he car?
 
pre-ignition can be caused by: too low octane fuel, incorrect timing, incorrect fuel/air mixture. you will hear this as a "pinking" sound.
these faults can be caused by a whole lot of items going wrong on the car. I would not leave it, rather get it checked as soon as you can.

if it turns out to be a bearing fault, then your engine will need overhauling. if you only have 69000 miles then it is unlikely to be a bearing.

when you get that ticking noise, does the car run roughly at first and then go smooth once the noise has gone?
if so, that is typical on audi's, caused by the hydraulic tappets rattling until the oil circulates. if you want to get rid of it, then I would change your oil to a fully synthetic oil. they have a much greater temperature opeating range than mineral oils and also do not break down as quickly.

of course it may be no more than one of the ancillery items touching something when it's warm.... :)
 
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