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My Rav 4 2006 2.2 diesel will accelerate when when engaging 3rd Gear from second with foot off the accelerator speed approximately 23 miles an hour


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While changing down gears slowing down to turn on to a T junction then engaging 3rd Gear the car will accelerate without my foot on the accelerator the only way to stop it it is by changing down Gear have you any suggestions what the cause could be

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Very odd.  Is the gearbox manual or auto?  What happens if you select Neutral?  

First thought is it could be a software malfunction - try disconnecting the Battery for (say) ten minutes.

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9 hours ago, Peter de-festa said:

While changing down gears slowing down to turn on to a T junction then engaging 3rd Gear the car will accelerate without my foot on the accelerator the only way to stop it it is by changing down Gear have you any suggestions what the cause could be

It is possible you are in too high a gear at too low a speed and the car even at engine idle speed is gaining speed due to the gearing which as you say stops when you shift down.

To confirm this find a quiet bit of flat road take off in first without throttle note the speed then shift up to second without throttle and note the speed and repeat 3rd , 4th etc these speeds will be the minimum speed capable in each gear

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10 hours ago, Devon Aygo said:

It is possible you are in too high a gear at too low a speed and the car even at engine idle speed is gaining speed due to the gearing which as you say stops when you shift down.

To confirm this find a quiet bit of flat road take off in first without throttle note the speed then shift up to second without throttle and note the speed and repeat 3rd , 4th etc these speeds will be the minimum speed capable in each gear

Can I also suggest that when you do this test you check the effect of gently touching the brake pedal a few times. When the brake servo vacuum is replenished the engine briefly draws in air which may increase rpm. This would be heightened if the servo diaphragm or valving is damaged.

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I agree with Devon Aygo, too high a gear for the speed required. 

I have been out in my 2010 2.2 d this afternoon with the following results. Tick-over revs are 8oo rpm. At tick-over the speeds are ; 1st gear = 8mph; 2nd gear = 12mph and 3rd gear =17mph.  To reach 23mph in 3rd gear I required about 1200 rpm. 

As a trial I set off from stationary, without using the accelerator, in 1st gear the car pulls straight up to 800rpm and 8mph. Without using the accelerator I then change into 2nd gear and the car pulls straight up to 800rpm and 12mph. Again without using the accelerator I changed into 3rd gear and the car pulled cleanly, and quite strongly, up to tick-over at 800 rpm and 17mph.  The thing to remember is that each time you change down in this trial the engine speed drops below the tick-over speed, at which time the ECU responds by taking the engine speed back up to tick-over. In 1st,2nd and 3rd gears the acceleration back up to tick-over can be quite a powerful serge.  I did try going into 4th gear but the low rpm coupled with the higher gear made the car struggle --- but it can be done. 

My initial advice would be to check the tick-over speed with a warm engine. If it is too high it can be adjusted by an auto-electrician. The next thing would be to simply use a lower gear.

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  • 2 weeks later...
On 4/15/2021 at 10:37 PM, Devon Aygo said:

It is possible you are in too high a gear at too low a speed and the car even at engine idle speed is gaining speed due to the gearing which as you say stops when you shift down.

To confirm this find a quiet bit of flat road take off in first without throttle note the speed then shift up to second without throttle and note the speed and repeat 3rd , 4th etc these speeds will be the minimum speed capable in each gear

Thanks for that I was under the same impression myself that sounds very feasible and we'll try to replicate on a long quiet Road in those gears

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On 4/15/2021 at 3:24 PM, IanML said:

Very odd.  Is the gearbox manual or auto?  What happens if you select Neutral?  

First thought is it could be a software malfunction - try disconnecting the battery for (say) ten minutes.

Hi hi it's a manual gearbox yes just connected the Battery for 20-minutes but no change

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