2015 Yaris 1.33 Sport - Jerky Acceleration

[Gray86]

Hi All,

we have a  2015 Yaris 1.33 Sport and have noticed a bit of stuttering / Jerky acceleration around 2,000rpm whilst cruising or accelerating gently when engine is warm. We have owned the car since it was 2 years old / 10k miles (now at 34k miles). I believe the issue has been there since we got it, however I think it is now more noticeable and more regular. 
 

originally I put it down to drive by wire throttle not being very smooth, but as it’s got worse I’m thinking it could be a fault. Toyota tried to diagnose it at its 3rd year service, but couldn’t replicate it. 
 

I'm thinking either - dirty injectors, dirty MAF, spark plugs getting tired in the first instance. . . Maybe lambda sensor (although no CEL). 
 

any ideas, or does everyone else have this issue and it’s just the drive by wire? 

[Mooly]

For the 1.33L try resetting the ECU by disconnecting the Battery for a few minutes. Do it with a cold engine and when you restart first allow it to idle for a couple of minutes before driving. The performance and feel will improve over the next few starts and as you put more miles on.

[Gray86]

14 minutes ago, Mooly said:

For the 1.33L try resetting the ECU by disconnecting the battery for a few minutes. Do it with a cold engine and when you restart first allow it to idle for a couple of minutes before driving. The performance and feel will improve over the next few starts and as you put more miles on.

Thanks, I’ll give this a go later! 

[Gerg]

I have an idea that the drive-by-wire throttle came into use (they seemed to start arriving in around 2006) as a means of getting the engine through tighter emissions regulations.  By removing absolute control of the throttle butterfly away from the driver, the ECU has an chance to dampen very rapid throttle movements that might cause engine hesitation, or throttle closures that would allow pockets of unburned fuel to go down the exhaust, which would potentially harm the emissions numbers.

So, I wouldn't have thought that the electronic throttle control is directly the cause of your hesitation, but that it arrived at the same time as tougher regulations, which it helped to allow to happen without ruining engine 'driveabilty'.

I've not seen any of the above written down, it just seemed logical to me that this is why it was implemented, so I'm happy for someone to correct this.

Your list of things to check looks good, and Mooly's suggestion also!

[TonyHSD]

I found both 1.33 and 1.6 Auris from 2010 to behave very similar with hesitant responses when accelerate. Both failed my liking and I went for a hybrid version which hasn’t got any of the above even though it’s same drive by wire thing. Shortly after my test drives I did older Toyota model with regular cable throttle and was pleasantly surprised how responsive is that car, kind of sporty feeling from a mpv. 👍

[scannerman]

I had this problem shortly after servicing the car (100K). I had changed the spark plugs, although the existing plugs weren't showing any signs of wear. The replacement plugs were sourced on eBay, big mistake, as after only a short time the tips were burning off (fake Iridium plugs). So off to a reliable Motor Factors, for a set of Bosch plugs, which wasn't as expensive as I had imagined, £40, and all is now well.

Part of my maintenance last summer was to check and clean the throttle body. I had found a lot of carbon deposit around the butterfly valve and intake throat, with toothbrush and cleaner all came up clean again and cleaned the MAF sensor with MAF sensor cleaner, apparently the cleaner is different from other cleaners and is required.

[Gray86]

On 1/24/2021 at 1:33 PM, scannerman said:

I had this problem shortly after servicing the car (100K). I had changed the spark plugs, although the existing plugs weren't showing any signs of wear. The replacement plugs were sourced on Ebay, big mistake, as after only a short time the tips were burning off (fake Iridium plugs). So off to a reliable Motor Factors, for a set of Bosch plugs, which wasn't as expensive as I had imagined, £40, and all is now well.

Part of my maintenance last summer was to check and clean the throttle body. I had found a lot of carbon deposit around the butterfly valve and intake throat, with toothbrush and cleaner all came up clean again and cleaned the MAF sensor with MAF sensor cleaner, apparently the cleaner is different from other cleaners and is required.

Great advice there - thanks! 
 

I’ve not yet tried disconnecting the Battery, although will do this after servicing. When I service it in March, I’ll be doing spark plugs too - I carefully ordered some genuine plugs from eBay (not fakes). 
 

Did cleaning the MAF & throttle body fix the issue? 

[scannerman]

19 minutes ago, Gray86 said:

Great advice there - thanks! 
 

I’ve not yet tried disconnecting the Battery, although will do this after servicing. When I service it in March, I’ll be doing spark plugs too - I carefully ordered some genuine plugs from eBay (not fakes). 
 

Did cleaning the MAF & throttle body fix the issue? 

I did the cleaning to prevent future possible problems rather than having to fix one. I also disconnected the Battery for a period to reset the ECU but this didn't solve the problem. The plugs was the issue with the jerky throttle response, could have left the original ones in as they are supposed to last 100k miles.

[TonyHSD]

Spark plugs bought from eBay are fine if you purchase them from official Toyota store or dealer , all others are fake, same for the oil filters, air filters etc. Fake parts are the worst for the car as they not only perform bad but can cause damage too, aftermarket quality parts are acceptable but fakes are full stop. Good you got rid of them. 

[Tintaglia]

I'm interested in this subject because I'm not happy with the throttle response on my 13.3 either.  I wouldn't say it is jerky but it is laggy and hangs on gear changes.  I've noticed that the hanging is worse when the engine is cold.  It runs and starts brilliantly but on just two occasions (in 7000 miles/2 years) it has coughed on picking up after a gear change.  It was not an individual cylinder misfiring, more like an electrical fault.  But there were no misfires recorded by the ECU using my VW software which is very limited and mainly useful for basic engine code reading on Toyotas.  I now have a Techstream cable and software so I need to get round to getting it working properly and having a better look at the live data just in case there are any hints as to why mine seems a bit worse than most others.    

I know the hanging is considered 'normal' but I think mine is worse than usual.  I have improved it by a basic mod to the clutch pedal/switch which I described in the 'How to' section but it still is not like any other Toyota I have driven.  I know the reasons given for it but no other make of car has it to this degree and it irritates the hell out of me!  I would happily pay for a dealer to update/reflash the ECU to cure this problem if such an update existed.

I will look at the MAF and throttle body but some of these things can be damaged by cleaning (even with care) so if they are recording the right numbers I will leave them.  Does anyone know if the throttle body can be calibrated to set it up as per factory with Techstream?  I remember this is part of fitting a throttle body on VW's.   

[Gerg]

1 hour ago, Tintaglia said:

Does anyone know if the throttle body can be calibrated to set it up as per factory with Techstream?  I remember this is part of fitting a throttle body on VW's.   

There is a copy of the Toyota iQ technical manual if you search on the iQ forum - is that engine similar enough to find out more on that topic?

In trying to think of slightly unusual faults that could make your car hesitant, what about a slightly leaking EGR valve?  This is pure speculation on my part - I've never seen one and have no idea if this is susceptible!  And I'm sure you've tried fuel injector cleaner, no?

[Tintaglia]

Thanks for the reply.  I'm hoping to be able to go through EGR flow and anything else that is available.  I don't know if the procedure for any possible calibration would be the same as the iQ but will have a look.  The problem for any testing is finding out normal range of what you should be expecting to see.  The fact that it is a little worse when its cold interests me.  I can watch what the coolant sensor is reporting live as it warms up and see that it looks sensible.  It would be good to know what the fuel trim is showing as a guide.  The software wouldn't work back when I first tried it and the seller sent me a undated driver but I haven't tried it yet. 

I am just in the process of making a smoke detector from a cheap Halloween smoke machine to look for vacuum leaks.  Seems like it worked ok in my lounge!  😄