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Engine revving by itself

Dozza

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Hi all,

VE auto SS here. It has recently started revving by itself. I'll be driving a long and the acceleration will "jab" when I don't have my foot on the accelerator. Sometimes it will rev up to 3000 RPM and stay there for a bit and then goes back down and corrects it self. The problem will then reoccur. There are no engine codes.

This problem only seems to occur on bigger drives, maybe after an hour of driving and then it will start. It doesn't happen driving around town for example.

Could this be a throttle body issue? It only seems to have started this after I had headers and extractors fitted.

Cheers
 
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greenacc

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I would guess throttle body issue but there must be an error code logged when this happens? Has you had the car scanned yet?
 

Dozza

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No code at all. My brother who is a mechanic has scanned it and no codes at all. He also thrinks throttle body.
 

Skylarking

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Connect a BT diagnostics dongle to your OBD port and use a phone app to monitor accelerator pedal position and revs... If you then see the accelerator position increasing when you are not pressing the accelerator, I’d say you have some fault in the pedal assembly electronics or wiring to ecu.

If the revs increase when the accelerator position hasn’t changed, I’d guess it’s the throttle plate motor or air bypass motor or their wiring but don’t know as haven’t had such problems myself...

Toyota had similar accelerator pedal issues known as unintended acceleration, something which caused accidents and deaths. The issue was caused by what’s known as “tin whiskers“ which occured through the use of lead free solder... But that was years ago so you’d thing such issues would have been resolved in all cars by now.
 

Dozza

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Hi guys,

I installed a new throttle body, took it for the usual drive and after 30 to 40 mins of driving started doing the same problem, after the same distance.

Anyone know what else this could be? It only seems to have started after we fitted new headers and cats. Still no engine codes popping up.

Cheers
 
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lazyc

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Look at the live data. Or even engineering mode throttle %.

When it plays up what else is going on?
Might be getting extra air from somewhere.. like a crack in a manifold that opens when it gets hot.

Otr? Still got a MAF? Using cruise at the time? Still got the turtle on the top?
 
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Dozza

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Yeah I've got an OTR with the MAF inbtween the OTR and the throttle body. By turtle on top are you referring to the engine cover? If so, yes it is on. No cruise control on at time of issue.

With scan tool connected, when it happens APP remains at 0% and the TPS was sitting at roughly 5% with no foot on throttle. When the issue occurred, the TPS spiked anywhere from 17%-30% with no foot on throttle.
 

lazyc

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Have you had a tune yet?
Is it using heaps of fuel?
Getting and staying at operating temp?
Good o2 readings?
Is the auto dropping a gear when this happens?
Edit, open road speeds?
What are you doing with the extra rpm?
What gear does the car report when this happens?
 
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Dozza

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Have you had a tune yet?
Is it using heaps of fuel?
Getting and staying at operating temp?
Good o2 readings?
Is the auto dropping a gear when this happens?
Edit, open road speeds?
What are you doing with the extra rpm?
What gear does the car report when this happens?
I've had it tuned. The problem was occurring before the tune and still after it. I took it back and they couldn't find anything wrong with it (it usually only happens after 40+ minutes of driving).
Not 100% sure. It says the average fuel at 5km/h is about 11L/100?
Operating temp seems table.
Not sure about 02 readings.
Yeah it does seem to do that.
I'm usually going about 100km/h and then it will occur when I need to slow down to about 60-80.
What do you mean about the extra rpm?

I spoke to a local performance shop (different mob) and they suggested possible throttle body (already tried) and then accelerator pedal possibly...
 
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