Fault that dealer cant locate - suspect VVTI problem

[RobbM]

I have a Verso S with the VVTI system.

Its a March 2011 model and has overed 13500 miles because it is our second car and we use it when we ned a second car.

Its been reliable until September this year when it developed a symptom that feels like the engine loses power and then regains the power again.

It feels like someone is pulling the handbrake on but the engine doesnt labour when it happens and the revs stay the same so the engine seems to be losing power which leads me to believe its the vvti SYSTEM.

I have tested this car in various conditions and have found it is worse when the ambient temperature is low - single figures for example. When the ambient temp is in double figures it gets better when the engine is at operating temperature.

It seems more likely to happen at about 2000 rpm which is about 30 mph in 4th gear.

I suspect the VVTI cam timing is changing for some reason which is why the engine seems to lose power without the revs changing.

The VVTi is operated by the ECU which takes its decison by readings from several sensors.

The engine diagnostic light doesnt come on and the dealer says "the fault may be because the throttle setting is very light at that speed and the ECU cant decide which setting so is switching between two settimngs - this is the way its designed and not a fault".

I have argued that the fault was never present before September and is worse at lower temperatures, plus I cant believe Toyota would design a car that exhibits this chracteristic which will annoy the drivers.

Th dealer has agreed to take it in and test it but warned me that they may not find any fault.

As the warranty expires at the end of March 2016 I would like some advIce how to get this sorted before the warranty expires.

Happy to answer any questions

Thanks in advance.

[FROSTYBALLS]

The only way around this would be to have a technician ride in the car with you to experience the fault if it appears. Other than that, try another Toyota dealer, but you risk the same occurring.

[RobbM]

Thanks for the quick reply, I have been for a test drive with a mechanic (he drove) and he did notice the symptoms and said he would see if there was anything from Toyota about this. When I called to chase the response and book the car in they explained that they might find that this is just the way the system works on this car.

[Devon Aygo]

/here is only one Technical service bulletin from Toyota regarding driveability ref:

EG-0097T-1112  

DESCRIPTION OF PHENOMENON

Some customers may experience engine jerking while driving on vehicles with Manual Transmission.

PRODUCTION CHANGE

The engine ECU software has been changed.

Vehicles built before 09/10/2012 reprogramme engine ECU with new software.

[fordulike]

I know this reply is a bit late and may be a stab in the dark, but could it be due to a dirty MAF sensor?

I used to own a Nissan Almera that had similar symptoms to what you describe, and I cleaned the MAF sensor and all was well again.

I found this website that describes how to do it: http://www.mafcleaning.co.uk

BTW, mine didn't show any fault codes on the scanner either!

[RobbM]

Thank you to Devon Aygo the reprogram of the ECU has cured the problem and the car is a pleasure to drive again.

best regards RobbM