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Old 01-02-2016, 02:43 PM   #1
jackmilas
 
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Cutoff at low RPM during gentle acceleration - Yaris Verso 1.3 VVTi [SOLVED]

I get short engine cutoff which causes jerky acceleration.
It happens at low RPM, around 1200, on each gear.
The best way to present the issue is to try to drive over a curb from complete stop. I have a steep entry to my garage, you can see in the video, where I keep the throttle gently and steadily pressed in: https://www.youtube.com/watch?v=Ll7Rh31lpc8

Other than that the car runs super smooth but there's a problem with fuel economy. Car's display shows 6.5l/100km average but real consumption is 8.5l/100km (calculated from distance driven and fuel tanked).

I exchanged Mass Air Flow sensor with my Prius but even with MAF sensor completely disconnected the issue stayed there. I ordered a new front O2 sensor but I get a feeling it will not sort it out.

Would anyone be able to help me before I go to Toyota dealership and before I spend too much money there?

Last edited by jackmilas; 02-19-2016 at 03:55 AM. Reason: SOLVED
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Old 01-02-2016, 11:21 PM   #2
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Cutoff at low RPM during gentle acceleration - Yaris Verso 1.3 VVTi

Are there any codes?

Can you still drive the car or does this only happen under light throttle application?


Sent from my iPod Touch
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Old 01-03-2016, 04:24 AM   #3
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Quote:
Originally Posted by Bluevitz-rs View Post
Are there any codes?

Can you still drive the car or does this only happen under light throttle application?


Sent from my iPod Touch
There are no codes when I check it with iPhone app OBD Fusion.

I can still drive the car. It happens only at light throttle at around 1200RPM and under a load. I can't reproduce it on neutral. In normal use it just gives me one or two "jumps" during light acceleration from complete stop. 1-2 out of 5 times it won't happen at all.

My guess is that ECU cuts the fuel off because some specific sensor values are met. Things that didn't help:

- disconnecting MAF sensor
- disconnecting both O2 sensors
- 98 octane fuel instead of 95
- injector cleaner fluid

The car has 140k kms, 15 years old.
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Old 01-03-2016, 08:38 AM   #4
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Can you see the reading of the throttle position sensor?
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Old 01-03-2016, 11:53 AM   #5
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Quote:
Originally Posted by Bluevitz-rs View Post
Can you see the reading of the throttle position sensor?

I just checked it. My default (throttle off) position is 11.8% and the engine cutoff happens at around 17%. Gentler or harder acceleration doesn't produce the problem.


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Old 01-03-2016, 11:54 AM   #6
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It's the reading steady and smooth all the way through the full range?
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Old 01-03-2016, 02:50 PM   #7
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It's the reading steady and smooth all the way through the full range?
It is.
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Old 01-03-2016, 03:26 PM   #8
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have you tried unplugging the TPS?

I can't think of anything else that would cause a light load hesitation at a certain throttle angle like what you're experiencing.
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Old 01-03-2016, 03:27 PM   #9
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Both Intake air and Coolant temps are reading normal?
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Old 01-03-2016, 03:44 PM   #10
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Quote:
Originally Posted by Bluevitz-rs View Post
have you tried unplugging the TPS?

I can't think of anything else that would cause a light load hesitation at a certain throttle angle like what you're experiencing.
I'll give it a go tomorrow.

Regarding temperature question - yes, they read normal.

But I forgot to add that the problem occurs after "cold engine" warning light goes out. When the light is on there is no jerky acceleration. As soon as the light disappears, the problem appears.
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Old 01-03-2016, 10:09 PM   #11
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Ok check and see if the problem only occurs when the Fuel system is in Open Loop or Closed Loop. Therefore it's a sensor problem somewhere.
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Old 01-04-2016, 06:42 AM   #12
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Quote:
Originally Posted by Bluevitz-rs View Post
Both Intake air and Coolant temps are reading normal?
I looked more carefully into intake temperature. Today the outside temperature was -8C. The intake air temperature was showing values between -1C and 1C.
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Old 01-04-2016, 08:20 AM   #13
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Originally Posted by Bluevitz-rs View Post
have you tried unplugging the TPS?
I did it today. No change.
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Old 01-04-2016, 08:45 AM   #14
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Quote:
Originally Posted by jackmilas View Post
I looked more carefully into intake temperature. Today the outside temperature was -8C. The intake air temperature was showing values between -1C and 1C.
that seem right.

I'm running out of ideas...

There is a code set every time you unplug a sensor and run the car right?
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Old 01-04-2016, 02:52 PM   #15
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Originally Posted by Bluevitz-rs View Post
that seem right.

I'm running out of ideas...

There is a code set every time you unplug a sensor and run the car right?
Yes, there was a check engine light and throttle sensor error.
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Old 01-04-2016, 03:59 PM   #16
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It's an automatic I'm assuming from the video...

I'm wondering if it's a transmission problem of some kind.
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Old 01-05-2016, 02:18 AM   #17
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Quote:
Originally Posted by Bluevitz-rs View Post
It's an automatic I'm assuming from the video...

I'm wondering if it's a transmission problem of some kind.
Can the transmission send "cut fuel" message to the ECU in those specific conditions?

- it happens only at a specific throttle position (even with throttle sensor disconnected)
- it happens only at low RPM range, around 1200-1400RPM
- it happens only when the cold engine warning goes out
- it happens at every gear

Today I'm replacing front O2 sensor and I'll report back if there has been any change. Some people say that 16 year old car with 140k kms will benefit from replacing O2 sensor in better fuel economy anyway. For some reason I am one of top Yaris Verso fuel consumers despite that I drive very economically: http://www.spritmonitor.de/en/detail/725585.html

The car is showing average fuel consumption at 6l/100kms (I reset it at each full tank) and in reality the car burns 8l/100kms. Perhaps both issues have the same root cause?
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Old 01-05-2016, 08:40 AM   #18
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Yeah a lazy front O2 sensor can cause poor fuel economy. It happened to me.

Have you tried disconnecting the battery and letting the computer reset?

I keep thinking it TPS related because I feel like somehow the ECU thinks the engine should be idling and sees a "fast" idle speed and cuts fuel to bring it back to idle.
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