Lumpy and Hesitant Throttle

[littlehomer]

Hey All,

I've got an old problem that's surfaced again. 1.9 Diesel Phase 2.

Throttle response is lumpy, hesitant and waves up and down when at certain revs and certain points of the throttle pedal. Normally very low throttle levels.

The only thing I can find is the below:

Pressure loss within a common rail fuel system can often result in one or more of the following symptoms, hard or difficult starting / erratic or uneven tick over or idle / lumpy running / hesitation on acceleration / smoke on tick over or acceleration / lack of power or even a total shut down of the system. One of the main reasons for pressure loss is due to excessive fuel being returned to the fuel tank, also known as back leakage. Once the injector/s suffers from excessive back leakage, the fuel pump cannot generate enough pressure to enable the system to operate. This is more pronounced at starting or tick over due to the fact that the pressure generated by the pump is directly related to the engine’s revolutions which are lower at start and tick over. In a colder climate the engine rotates slightly slower thus lower pump pressure whilst with warmer fuel the viscosity is thinner thus allowing worn parts to leak more.

So, the question is, how would I fix it if I am getting this business?

Are we talking new injectors?

Cheers,

Daniel

[Biotoxic]

hmmm.. Air or water in system, some crack in turbo case..... couple of places to check

[andy_d]

leak test on the injectors perhaps?

[littlehomer]

Hey up,

It's a new refurbished turbo. £486.

The car has done this before. So I doubt it's related to this.

Unless they've given me a duff turbo. But it's a BTN one.

Throttle potentiometer? It's fly by wire........

When you say air or water in the system, where and what system?

Perhaps some fuel additive to kill the bottom of the tank water etc?

Cheers,

Daniel

[Biotoxic]

Originally Posted by littlehomer

Hey up,


When you say air or water in the system, where and what system?

Cheers,

Daniel

Sorry, I meant air or water in fuel delivery system, between diesel pump and injectors, I think I read about this in this forum before I registered here. It was something like, if the air or water gets trapped in common rail system, its hard to get out and car could lose power for short while .. all your symptoms above, If my memory serves me correctly, you should check fuel pressure sensor or something, drain water from diesel filter housing and then try again.

[littlehomer]

Ah now, you say, drain the fuel filter of water.

I've changed the fuel filter as regularly as I should.

How do I drain it? Is there a drain screw?

Cheers,

Daniel

[Biotoxic]

yes under that fuel filter housing, there is a bolt or something, I have never done this, bet there is instruction on vadis. Replacing the fuel filter or draining off water, its called.

[littlehomer]

It's a start!

I'll try that and report back.

Many Thanks,

Daniel