Anyone know

[whereskeith]

Hi All.
This question is for anyone with some technical knowledge on GS or 4200.
If I keep the car steady at say 3000rpm in 2nd or 3rd gear and maintain , there is a blip for a split second as if you suddenly take you foot of the throttle and the put it back. It’s not jerky , it’s like a complete loss of power for a split second but the revs don’t drop. It happens a quite a lot but not with a regularity that you could measure.
Is that likely to be throttle sensor wear ? I changed the plugs on the last service and it’s not that.
It accelerates without any issues and in higher revs on a motorway there is no issue.
Thx .

 

[2b1ask1]

Have you done a throttle reset recently? It would be my first step.

 

[whereskeith]

No, any idea how would I do that ?

 

[hashluck]

Closed throttle resetting
1/. Put gear selector/lever in neutral.
2/. Flick accelerator pedal a couple of times with the edge of your shoe to ensure full return is achieved.
3/. Switch ignition 'round as far as MAR.
4/. DO NOT START ENGINE!
5/. Leave all pedals and switches alone for at least 2 minutes.
6/. Switch off ignition.

Full throttle resetting
1/. Put gear selector/lever in neutral.
2/. Switch ignition 'round as far as MAR.
3/. DO NOT START ENGINE!
4/. Gently depress accelerator pedal to full extent of its travel and keep it there for 5 seconds.
5/. Release throttle.
6/. Switch off ignition.

 

[whereskeith]

Closed throttle resetting
1/. Put gear selector/lever in neutral.
2/. Flick accelerator pedal a couple of times with the edge of your shoe to ensure full return is achieved.
3/. Switch ignition 'round as far as MAR.
4/. DO NOT START ENGINE!
5/. Leave all pedals and switches alone for at least 2 minutes.
6/. Switch off ignition.

Full throttle resetting
1/. Put gear selector/lever in neutral.
2/. Switch ignition 'round as far as MAR.
3/. DO NOT START ENGINE!
4/. Gently depress accelerator pedal to full extent of its travel and keep it there for 5 seconds.
5/. Release throttle.
6/. Switch off ignition.

Thx

 

[whereskeith]

that does not seem to have sorted the issue..

 

[allandwf]

Do you have any pending fault codes? It may be a quick blip on a coilpack etc. It wont bring up a CEL until it's been in for a predetermined time.

 

[whereskeith]

Do you have any pending fault codes? It may be a quick blip on a coilpack etc. It wont bring up a CEL until it's been in for a predetermined time.

I do not have a code reader so no idea . Does it state anything on the display when there are codes pending?

 

[allandwf]

Any cheap reader will do. It will tell you if they are pending or standing.

 

[Oneball]

You can get a basic code reader for less than £50, I've got a little Clarke one that now sits permanently in the boot of my 3200 .

If the car is in gear the revs aren't going to change as the wheels are turning the engine so if they don't change it's not going to be gearbox or clutch.

Other thoughts are:

Did you use the right plugs?
What are the air filters like?
When was the fuel filter last changed?
Is the fuel tank breather working?

 

[whereskeith]

You can get a basic code reader for less than £50, I've got a little Clarke one that now sits permanently in the boot of my 3200 .

If the car is in gear the revs aren't going to change as the wheels are turning the engine so if they don't change it's not going to be gearbox or clutch.

Other thoughts are:

Did you use the right plugs?
What are the air filters like?
When was the fuel filter last changed?
Is the fuel tank breather working?

Plugs changed on last service , I use iridium plugs.
Air filter changed last service.
Fuel filter... could be that
Fuel tank breather... I did notice I seemed worse after filling tank with fuel , would that be a link ?

 

[whereskeith]

It’s weird it’s like a misfire but you feel a jerk of lost power for a split second then back to normal.

 

[Oneball]

Plugs changed on last service , I use iridium plugs.
Air filter changed last service.
Fuel filter... could be that
Fuel tank breather... I did notice I seemed worse after filling tank with fuel , would that be a link ?

We’re the plugs the correct spec? There’s different heat ranges that could cause an issue.

If it seems worse when the tank is full it would be worth looking at the tank breather system. I’m not up on 4200 but there will be a breather pipe from the tank that will connect to a solenoid valve which will also be connected to the manifold vacuum and a carbon canister.

 

[allandwf]

It’s weird it’s like a misfire but you feel a jerk of lost power for a split second then back to normal.

It does sound like a split second loss of spark.