Heavy Pinking

[peterc.lewis@blueyonder.co.uk]

I posted a while ago about pinking under load when towing.

I thought it had gone when I filled with petrol from another source but it appears to be back now. It's quite loud too but only under load. There is no apparent loss of power but the noise is quite pronounced.

The car has done 140000 miles (just run in then) and I've done the vast majority of the work on it since I've had it.

Apart from the usual ignition key problem that all Avensis seem to go down with it has been a great family car.

Any thoughts?

[Q.S.]

I posted a while ago about pinking under load when towing.

I thought it had gone when I filled with petrol from another source but it appears to be back now. It's quite loud too but only under load. There is no apparent loss of power but the noise is quite pronounced.

The car has done 140000 miles (just run in then) and I've done the vast majority of the work on it since I've had it.

Apart from the usual ignition key problem that all Avensis seem to go down with it has been a great family car.

Any thoughts?

Pinking (or detonation to be correct) is usually caused by one of two things,

1.) Ignition timing too far advanced

2.) A weak mixture

However, if you have ruled out both of these and bearing in mind the mileage of this vehicle, it could be due to carbon deposits in the combustion chamber (on the piston crown or the cylinder head). These can get rather hot and ignite the fuel/air mixture before the spark actually occurs.

The other symptom you might get from these deposits is running on, where the engine tries to keep running after the ignition is turned off but only with carburettor models which can still draw fuel. Fuel injection models wont draw fuel once the ignition is off as the injectors are switched off.

[Beagh1958]

To peterc,

QS has pretty much covered all bases with his reply. I am afraid you have to many variables with this one to allow for guessing (which will empty your pocket) ie: knock sensor or ign - module. I would certainly pay for an hr's diagnostics with this problem via a local inde garage or straight to your local Toyota dealer.

Regards, Beagh.