Stop Jerking Around! Jumpin Jumpin

[mrteach1973]

So after some advice if anyone can help.

When I switch the car on, the revs are around 1300, but when I put it in reverse they drop to around 800.

Thats not the prob though.

When I start to reverse with no gas, the car gently jerks / bounces like its got kangaroo petrol in it.

When driving I can also feel this when the I am not applying a great deal of gas.

Anyone have any ideas of what this could be. It just doesnt seem very smooth. Fine when you floor it, but otherwise a little jumpy.

Many thanks in advance.

[Mr Vlad]

Hi Roger. Is your car auto or manual? What sort of service history has it and what's its mileage? 

[Linas.P]

So just to clarify what is the issue here - are you saying your gear changes are not smooth, or that throttle response is not smooth? What throws me out a little bit, is that you saying "when I am not applying great deal of gas", which would indicate you are cruising... at which point I am a little bit confused how car can be jerky when cruising. Or you saying you slowly accelerating?

I assume it is auto (the advice on the manual would be totally different) and focus on driving here, as as far as I can see there is no issue with what you describing about moving off from stand still. 

The first bit about RPM is as expected, on cold start, especially cold winter morning the car will run 1300RPM idle with no load and will drop to 800RMP idle when you put it in gear, that is normal until engine and gearbox warms-up. Engine actually warms-up much quicker than gearbox and you may need to drive for a while to get it warm in winter, meaning that if you have 10 min drive to the shop... it may not actually be enough to warm the gearbox. Cold gearbox = thicker cold fluid /lower viscosity = gearbox may be a bit lazy to shift (kind of opposite from jerky, but definitions vary from person to person).

As well if you stationary in gear and just let-off the brake suddenly, then there will be momentary delay (I don't know.. maybe 0.5s) and it will jerk a little bit out of stand still, again normal.

Both throttle response and gear changes are controlled by ECU and it is so called "smart" which learns your driving style - so you were driving hard for sometimes it may become jerky as it expect to be pushed all the time. This can be re-set by disconnecting Battery for 10-15 minutes and then driving in your desired way. So that may be all it needs.

The next step, if the gear changes are late, early, or harsh - then it could be issue with fluid and it may need refreshing. But before you do anything, just make sure that car is still doing even when it is up to proper temp, because if you looking for the issue in the car straight after starting it on the cold winter morning, then you will find many issues which do not actually exist. 

[nicnac]

2 hours ago, mrteach1973 said:

So after some advice if anyone can help.

When I switch the car on, the revs are around 1300, but when I put it in reverse they drop to around 800.

Thats not the prob though.

When I start to reverse with no gas, the car gently jerks / bounces like its got kangaroo petrol in it.

When driving I can also feel this when the I am not applying a great deal of gas.

Anyone have any ideas of what this could be. It just doesnt seem very smooth. Fine when you floor it, but otherwise a little jumpy.

Many thanks in advance.

One possibility if auto box is that you have a transmission leak and your level is low and  incorrect . I have seen a box with a leaking driveshaft seal which over a period of time has lowered the fluid level to an unacceptable level causing these symptoms 

[mrteach1973]

18 hours ago, Mr Vlad said:

Hi Roger. Is your car auto or manual? What sort of service history has it and what's its mileage? 

Hi Auto with padels around 85000 miles an an incomplete service.

[mrteach1973]

17 hours ago, Linas.P said:

So just to clarify what is the issue here - are you saying your gear changes are not smooth, or that throttle response is not smooth? What throws me out a little bit, is that you saying "when I am not applying great deal of gas", which would indicate you are cruising... at which point I am a little bit confused how car can be jerky when cruising. Or you saying you slowly accelerating?

I assume it is auto (the advice on the manual would be totally different) and focus on driving here, as as far as I can see there is no issue with what you describing about moving off from stand still. 

The first bit about RPM is as expected, on cold start, especially cold winter morning the car will run 1300RPM idle with no load and will drop to 800RMP idle when you put it in gear, that is normal until engine and gearbox warms-up. Engine actually warms-up much quicker than gearbox and you may need to drive for a while to get it warm in winter, meaning that if you have 10 min drive to the shop... it may not actually be enough to warm the gearbox. Cold gearbox = thicker cold fluid /lower viscosity = gearbox may be a bit lazy to shift (kind of opposite from jerky, but definitions vary from person to person).

As well if you stationary in gear and just let-off the brake suddenly, then there will be momentary delay (I don't know.. maybe 0.5s) and it will jerk a little bit out of stand still, again normal.

Both throttle response and gear changes are controlled by ECU and it is so called "smart" which learns your driving style - so you were driving hard for sometimes it may become jerky as it expect to be pushed all the time. This can be re-set by disconnecting battery for 10-15 minutes and then driving in your desired way. So that may be all it needs.

The next step, if the gear changes are late, early, or harsh - then it could be issue with fluid and it may need refreshing. But before you do anything, just make sure that car is still doing even when it is up to proper temp, because if you looking for the issue in the car straight after starting it on the cold winter morning, then you will find many issues which do not actually exist. 

Ah ok. Will i need the Battery code if I disconnect?