[moulam]

My P38 diesel auto is an absolute joy to drive apart from one issue. When accelerating it jumps up to 3000 rpm and surges between 3000 and 3100 rpm until it changes gear. This has been getting increasingly worse and it is now nearly impossible to accelerate gently as it jumps straight up to 3000 rpm and sits there. It occurs under acceleration and mostly jumps from around 2200 rpm straight to 3000 rpm.

I have tried a full service including gearbox filter and fluid and this has not greatly improved things. I have also replaced the tank fuel pump because it did not register correctly on the fuel gauge (fixed the gauge issue but no help with surging)

Any help would be greatly appreciated as I am getting fed up with being thrown about in my seat.

Thanks

Edd

 

[gencybay]

Datatek's your man but I would guess that this is the throttle potentiometer saying night-night.

Could you visit the new member section and do the introductions?

G~

 

[dogsbody]

The throttle control and tick-over settings are electronic. You'd do well to get it hooked up to some decent diagnostics before you spend any more money.

 

[wammers]

What's it like static. Is the throttle progressive then or does it still jump around?

 

[Datatek]

Datatek's your man but I would guess that this is the throttle potentiometer saying night-night.

Could you visit the new member section and do the introductions?

G~

Unlikely to be the throttle pot but not impossible, only diagnostics would show that. Sounds like the box to me, could try some Lucas Transmission fix.

 

[wammers]

Unlikely to be the throttle pot but not impossible, only diagnostics would show that. Sounds like the box to me, could try some Lucas Transmission fix.

Yes does to me, like the box hunting for a gear. But asked the question about the throttle for elimination purposes.

 

[Datatek]

Yes does to me, like the box hunting for a gear. But asked the question about the throttle for elimination purposes.

Fair enough Tony and you told him how to do a basic check

 

[moulam]

I will play around later today to see what it is like stationary but i was unsure if it was the box because even if i drive with the gearbox selected in 1st or 2nd etc it still surges up to 3000rpm as before and then settles down a bit after that.

It has even started to do it at around 70 with the cruise control on, its not so bad but it is still jerky and you can feel the surge.

I will hopefully be able to tell some more this week as i have it booked in to be plugged in one evening this week.

I also seem to be getting less mpg as it has got worse as i am getting around 300-330 miles to a tank where i was getting much nearer 400 when i first got it.

 

[Saint.V8]

I am inclined to think Gearbox similar to Datatek....

 

[Datatek]

I will play around later today to see what it is like stationary but i was unsure if it was the box because even if i drive with the gearbox selected in 1st or 2nd etc it still surges up to 3000rpm as before and then settles down a bit after that.

It has even started to do it at around 70 with the cruise control on, its not so bad but it is still jerky and you can feel the surge.

I will hopefully be able to tell some more this week as i have it booked in to be plugged in one evening this week.

I also seem to be getting less mpg as it has got worse as i am getting around 300-330 miles to a tank where i was getting much nearer 400 when i first got it.

I'd check the oil level in the box before you use it again. Low oil level can cause slip and it will destroy the box PDQ. May already be too late
Clutch slip will also affect MPG.

 

[wammers]

I am inclined to think Gearbox similar to Datatek....

Eliminate possibilities, the easy ones first.