Engine revs without my input.

[Tafia]

Since we have owned our 2012 Auris it has given us no trouble at all except that now and again, usually when changing gear, the engine would increase it's revs a little with no extra throttle input from the driver. Both my wife and I had the same issue.

However, today as I was parking and had come to a halt, the engine screamed to 5000 revs whilst my foot was not on the throttle at all. This could be highly dangerous if it happened in traffic.

The main dealer has tried to find this fault but has failed, probably because it is intermittent. Anyone else had this issue or have an idea what the cause might be?

Thanks,

 

T

[TonyHSD]

If the car has never had throttle body cleaning done it’s good time to start from there. Very often especially in a hot days if the throttle valve is dirty may cause similar engine behaviour and no trouble codes will be generated so technicians can’t find the problem with diagnostic tool.  Get it clean and inspected by someone with experience , don’t forget to disconnect the Battery before work to reset the engine ecu. 

Regards 

[Tafia]

Many thanks for your prompt response. Any idea why that would cause the engine to rev up to 5000 or would a dirty throttle body cause the throttle to stick open at whatever the pedal position was set to at the time? It actually revs up by itself and, as you say, the fault would be hard to  find as it it intermittent

Thanks again.

T

[Heidfirst]

2 hours ago, Tafia said:

Since we have owned our 2012 Auris it has given us no trouble at all except that now and again, usually when changing gear, the engine would increase it's revs a little with no extra throttle input from the driver. Both my wife and I had the same issue.

This is actually normal behaviour by design.

However, today as I was parking and had come to a halt, the engine screamed to 5000 revs whilst my foot was not on the throttle at all. This could be highly dangerous if it happened in traffic.

This is not!

 

[Tafia]

Thanks for this. Odd that the changes in revs is designed into the car. I wonder what purpose that serves. I note that when the car is idling the revs can go up and down a little

 

Following the post from Tony HSD I have bought some Redex fuel system cleaner to see if that makes a difference though it may be hard to tell as the fault is intermittent. My concern is that whilst I can deal with the problem if it happens on the road, my wife, who owns the car may not be able to. It used to happen with a Nissan Laurel I owned many years ago though that had a much simpler throttle system, Just a wire connected to the pedal.

Happy days. 🙂

 

[furtula]

Car revving a bit before gear change should be related to emissions, and it makes gear changing smoother.

My old 2004 mazda 3 made a nice oomph every time you want to change at around 3.5k rpm or higher, always put a smile on my face.

It had wire throttle, so you could see easily enough that it was done by the ECU.

[TonyHSD]

Yes , there are some factory settings to increase rpm while changing gears but if engine pulsating on idle it’s more something that needs attention than that. Redex it’s fine , I also use it once in a while but redex it’s a fuel system cleaner and will not help with cleaning the throttle body where only air passes through. If fuel supplies is the problem engine will cough and possibly stall, when air supply is inconsistent will rise the rpm and pulsating. Throttle body may not be the reason every time but is common issue with the time when carbon deposits buildup, there maybe a vacuum leak or dirty MAF/MAP sensors for example but the car needs to be checked. I suggest body cleaning as a maintenance procedure only, can’t say for sure will fix the problem., and also after cleaning the engine will misbehaving for a little while, this is normal but will settle after that and will be smoother and more responsive. Same as on the hybrids egr , egr pipe, throttle body and intake manifold cleaning procedure. 

Regards. 

[Tafia]

Many thanks Tony and everyone. I wish Tony worked at my local Toyota dealers. Twice they have failed to do a thorough service and last time they claimed to have checked the brake fluid level when they clearly had not. I know this because when the car came back after the last full service I noticed the brake fluid reservoir was over-filled by quite a lot. The main dealer had not done this - a local garage had renewed three brake pipes and they were the ones who over-filled the reservoir - but if the dealers chap had really checked the levels he would have seen the over-filled reservoir. I went to the local garage for the pipes after being quoted £400 by the main dealer to have two pipes replaced. Bill from local garage was £180 for three. Then he spoiled himself by overfilling. Otherwise he did a very neat job.

As mentioned I have already asked the main dealer twice to find the cause of the revving engine and they found nothing. They didn't even think of doing what Tony has suggested. Can I trust them to have a look at the throttle body? WIll a competent local garage be able to do this work or does it require another trip to the Toyota dealer and hope this time he does what he is paid to do.

[TonyHSD]

Hi,

the main dealers technicians most of the times knows very well what is all about but they have rules that follow. They also don’t clean throttle bodies but wait until it’s properly clogged and triggered a fault code than they will offer a change with new at cost of hundreds of pounds , it’s a business and we are forum for sharing experience and help each other. If you know some good mechanic or local garage that you can trust, you can explain them the car behaviour than ask them to look at the body, not so difficult and if it’s dirty they can clean it.  It’s not a repair nor guarantee that will fix the problems, it is just like periodic maintenance for all petrol cars that has 50-60k plus miles and older than 5 years. If the car doesn’t do it all the times maybe just leave it like that, and if you get a engine management light on than you can have the car hooked to the diagnostics anywhere and you can have the fault code that will point you to the direction of the things straightforward. 

Regards 

[Tafia]

Thanks again for all replies, especially Tony. Very much appreciated. The car has done 40 K and is 2012 vintage. It has never let us down and, other than this revving issue, has been fine.  I will take it to my local garage and see if they can have a  peep at the throtle body.