Yaris Verso engine timing issue ... ?

[evalon]

Hi Toyota Yaris owners,

I have an issue with my Toyota Yaris (Verso from end 1999) that I hope one of you may be able to help with. It is an issue that does also pose challenges to my otherwise very competent mechanic - but I am thinking that somewhere in the world there may just be someone who knows what this is about ... ?? And since I really like the car I would much prefer finding a solution to this issue, if possible ...

A few words about the engine: The engine now has driven just about 270.000 kms, and apart from the issue I am about to describe, it works very well - no oil use (at all), and when connected to a diagnostic unit shows no faults or errors. It is a 1.3l engine. Spark plugs were replaced ~ 20.000 kms ago so they should be fine for another 12.000 kms. According to my mechanic the "air inlet sensor" was slightly off specs and has been replaced about a year ago (not original Toyota but should be ok - was new). This might have improved matters for a bit of time but I am not sure about it ... 

However, the issue is that:

Particularly when the engine is cold it is as if it may misfire - it feels as if the car "halts & goes" to some degree. It is a slow "halt & go" (maybe with a frequency of 1 - 2 Hz) at speeds of around 15 km/h to 45 km/h. At higher speeds I reckon the overall inertia of the engine & car reduces the "misfiring" so that it is less perceptible - although it is still there (I gear up to e.g. 4th or 5th gear so the engine also has low rpms). For some reason this seems to be augmented when the car has not been used for a couple of days (and the weather is cold).

Also, again mostly at lower speeds, when I press the speeder pedal in the beginning it is as if nothing really happens (it may actually decelerate) - but after a couple of seconds  - the engine sort of catches on and starts accelerating. My mechanic says that it may be because Toyota was keen on keeping fuel consumption low in the Yaris, and thus set the "base fuel injection level" a little too low to work entirely well particularly when the car is cold ... 

Anyway, after a few minutes of driving - or when the engine begins to warm up - these phenomena begin to mostly disappear. However, they are still ever so slightly there even when the car has driven maybe 50 kms. And occasionally, particularly when making a rapid acceleration, the engine misfires - just once or maybe twice during an acceleration. 

I hope this may be a useful description ... and if one of you knows what this may be about I would much appreciate hearing about it ;-)

Cheers & thanks,

Jesper 

 

[Madasafish]

Idle speed stepper motor not working properly - common fault.Waxstat fed by a small pipe which gets blocked. Solution is to drain coolant, flush, replace coolant and antifreeze and clean out pipe..with an airline(Car Mechanics March 2004... )

[evalon]

1 hour ago, Madasafish said:

Idle speed stepper motor not working properly - common fault.Waxstat fed by a small pipe which gets blocked. Solution is to drain coolant, flush, replace coolant and antifreeze and clean out pipe..with an airline(Car Mechanics March 2004... )

Hi Madasafish - thanks so much for your feedback. I will see if I can get hold of the March 2004 Car Mechanics issue and let my mechanic take a look at it. Will be GREAT if this proves to be the fault   ... Cheers, Jesper