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2009 1.0 Litre Engine stumbles briefly around 1500 rpm

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Hi, I'm after a little advice please.


I bought a 2009 1.0 litre Yaris this week and although it has done 90k it's in good condition and plenty of service history.

I have noticed that coming off idle, when the car reaches about 1500 rpm the engine stumbles a little and then with a few more revs clears up completely.

I have taken the throttle body off and cleaned it carefully with a toothbrush and carb cleaner but the issue still remains. The air cleaner was new.

It isn't a major niggle but I would like to sort it if possible.


Additionally, I gave our old Honda Jazz to our son but have noticed that the 3 cylinder engine in the Yaris is  noisier mechanically, almost a little tappety but definitely not timing chain or engine knock.  Reading about these it seems that this may be normal for this range of engines, Any thoughts ?


Thanks Darryl


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Plugs first check

Then clean MAF sensor. (great care needed)

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The car has paperwork showing a service including plugs less than 1k miles ago .

The air cleaner has definitely been renewed but I never accept a service receipt as accurately reflecting work done.

MAF cleaned today

If the plugs are a likely issue I will take them out tomorrow and physically check.

Any particulatr brand and ref no recommended?  I normally go for NGK


Thanks Darryl

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The first thing I noticed about the new model Yaris was that the 3 cylinder engine was much noisier the the previous 4 pot.

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Thanks all, I removed and carefully cleaned the throttle body but mistakenly said that I cleaned the MAF. My understanding is that my 2009 has no separate MAF, it certainly has no throttle cable. Obviously drive by wire.

If the weather holds today I'll have a look at the plugs.


My understanding is that the original specified Densos ( SK20HR 11 ) have been superseded by DENSO Spark Plug [K16R-U11]  and the  NGK equivalent is

BKR5EYA-11 .

There doesn't seem anything ominous in the noise from the engine but I am surprised at how much mechanical noise there is from it. The accompanying  service receipt states Fully synthetic Oil was used but no mention of viscocity .

so that is another thing to probably consider.

I may just change it anyway to make sure I know what is in there.

Thanks Darryl

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