Corolla vibration

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Wed 30 May 2007 16:35
Corolla vibration - John D
Our 52 plate Toyota Corolla 1.6 VVTI 37,000 miles has developed a vibration which is rpm dependent, and is loudest under light load and when the engine is up to full working temperature. It is centred around 1,600 rpm and disappears 100 rpm or so, above or below 1,600. The engine runs quietly with the throttle closed, under gentle throttle sounds normal as rpm increases, but produces this intrusive rattle as it goes through 1,600 and then is sweet all the way to 6,000 rpm. With the throttle pedal half way down or more, it is almost non-existent. It is much less noticeable when the engine is cold and it flew through the emissions test with flying colours at the MoT. Performance and fuel consumption are good (although the best torque is found much lower in the rev range than I would have expected from a 16valve Toyota).

The best way I can describe the sound is that it?s like a sheet of thick plastic which is picking up a resonance.

Under the bonnet, the noise seems to come from around the plastic inlet manifold. I took this off, expecting to be able to dismantle it further but it?s a sealed unit. Underneath I realised the exhaust heat shields all twang & vibrate, so I damped these using high temperature silicone and damping blocks. Quieter it was, but the root cause is still there.

Would anyone have any suggestions please? Would an injector cause this sound?

Many thanks, John
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