Rattling noise on light throttle - what is it?

Car - 1984 Saab 900 Turbo 16V. 184K miles

Problem - when lifting off the throttle, there is a harsh rattling noise. Only started today, was doing around 75mph in 5th gear on a constant throttle, then lifted slightly. There is a harsh metallic rattling noise that appears when I do this from somewhere in the engine. As I reapply the power, when the engine is in that state "where it's neither under load, or on the overrun" IYKWIM, the noise reappears. It only happens on light throttle, and the engine sounds sweet at any other time. Sounds like a bearing somewhere, but what? Small end? Camshaft? Timing chain slack? I know it's not a big end as I know what they sound like :-(

Thanks! Mike

Reply to
Mike P
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Sounds like it might be the heat stove rattling

Stuart

Reply to
Stuart Gray

Could be small ends I suppose. If it is, you should be able to reproduce it with the car stationary. Mike.

Reply to
Mike G

Piston slap can sound like small ends, but the noise usually reduces at high temperature whereas small ends get a little noisier. Thicker oil needed?

Reply to
SteveB

Does this engine have a hot air pick up, or turbo heatshield that could be rattliung? or an exhaust clip thats loose?

Also does the gearbox have an idler gear which could have got failing bearings, and only when there is slack in the driveline does it make a noise?

Tim..

Reply to
Tim (Remove NOSPAM.

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