Surging with cruise control

[hinsch]

The Pajero feels like it is surging when cruise control is selected on, through the complete range more noticeable above about 80kph, with cruise control selected off and hold a steady accelerator seems to be OK, any thoughts on a possible cause.
Have not even started trying to fault find, TIA

[Dalma01]

The Pajero feels like it is surging when cruise control is selected on, through the complete range more noticeable above about 80kph, with cruise control selected off and hold a steady accelerator seems to be OK, any thoughts on a possible cause.
Have not even started trying to fault find, TIA

Have you fitted bigger tyres?
Sometimes the torque converter keeps locking and unlocking.
Hence the surge.

[Muzza]

The Pajero feels like it is surging when cruise control is selected on, through the complete range more noticeable above about 80kph, with cruise control selected off and hold a steady accelerator seems to be OK, any thoughts on a possible cause.
Have not even started trying to fault find, TIA

I have had this since new , only on open highways, like the Hume Hwy, the vehicle surges, +/- about 1km can’t see it on speedo, but can pick it on boost gauge, it doesn’t do it on single lane country roads, or any if there is load on vehicle like a headwind etc
Dealer couldn’t find the problem ( no surprises there).
Good luck with finding it, I reckon it’s in the boost controller
Cheers

[gazza11]

I have an NT Diesel and it has done it since new, again on the open road like the Express Way and when going down a hill. Seems to be when on light throttle. Dealer made no reply when mentioned and has not gotten any worse over the years.

[Pushbike]

My experience of surging on cruise control has been with a petrol engine and occurred when cresting a hill. At times so scary I had to apply the brakes to drop out of cruise control.

A petrol engine with an automatic transmission has feedback (vacuum) from the inlet manifold to the transmission unit via a "modulator". I've had this modulator replaced during a service on a petrol engine.
Does a diesel engine have this type of feedback?
Is the feedback path, in whatever form, "sticky"?

[Pajshomoneroguntero]

I’ve just put it down to being a poorly tuned from design stage cruise control.

[Ky1e]

How many k's on it?
Surging on a diesel paj is usually caused by wear in the suction control valve. (valve which regulates your injector pump output pressure)

[farcanal]

Sold my NP at 280,000 kliks.
Never a hint of surging and used cruise all the time.

[hinsch]

Have you fitted bigger tyres?
Sometimes the torque converter keeps locking and unlocking.
Hence the surge.

It’s a manual 2014 diesel so the gearbox can be ruled out I think

[hinsch]

I have had this since new , only on open highways, like the Hume Hwy, the vehicle surges, +/- about 1km can’t see it on speedo, but can pick it on boost gauge, it doesn’t do it on single lane country roads, or any if there is load on vehicle like a headwind etc
Dealer couldn’t find the problem ( no surprises there).
Good luck with finding it, I reckon it’s in the boost controller
Cheers

Similar problem like it’s a bit of a lazy cruise control , cruise control misses the set speed then goes are f... I better get this thing going again back up to set speed it’s only a kilometre per hr or two but noticeable

[spot01]

Similar problem like it’s a bit of a lazy cruise control , cruise control misses the set speed then goes are f... I better get this thing going again back up to set speed it’s only a kilometre per hr or two but noticeable

Thats normal for these cars on undulating roads - I've had several & they have all been the same. The cruise control is really only meant for flat roads.