2010 Passat 2.0 TDI - Erratic/fluctuating revs at idle

Thanks everyone for suggestions and advice.

I got some more live data via the OBD scanner. The fault code causing this seems to be P1065 - Fuel pressure regulation control difference.

The pressure rises to around 300 bar and then drops down to below 50 bar at a cycling frequency of probably half a second.

The information that I have indicates a number of possible causes - all of which we have checked other than the high pressure fuel pump.

A replacement HPFP has arrived today and hopefully I can get it fitted next week.

Will update as to how it goes.

Cheers

Before you restart, thoroughly bleed the system by running the in tank pump and if fitted, the electric high pressure fuel pump. Do this for at least a minute.

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Originally Posted by Crasher

Before you restart, thoroughly bleed the system by running the in tank pump and if fitted, the electric high pressure fuel pump. Do this for at least a minute.

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Many thanks for this advice.

Can I ask the reason for doing this?

The gears inside the pump run directly on the aluminium and the fuel is the lubricant, when it runs dry the pump can be destroyed in seconds and send aluminium swarf into the injectors which you can’t get out. It is common for the HPFP to fail just after a filter change and CAN indicate the person doing the job did not bleed the system and this process is not optional. If the pump fails and fills the fuel system with swarf, putting the damage right using all genuine parts and main dealer labour comes to over £6k.

Quote:

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Originally Posted by Crasher

The gears inside the pump run directly on the aluminium and the fuel is the lubricant, when it runs dry the pump can be destroyed in seconds and send aluminium swarf into the injectors which you can’t get out. It is common for the HPFP to fail just after a filter change and CAN indicate the person doing the job did not bleed the system and this process is not optional. If the pump fails and fills the fuel system with swarf, putting the damage right using all genuine parts and main dealer labour comes to over £6k.

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Thanks again, Crasher :beerchug:

I will make sure this process is carried out.

Hopefully doing the job tomorrow. Fingers crossed!

Bad news...

Had the HPFP changed over today.

Problem remains as before.

Little bit stumped...

IF the HPFP had eaten its internals AND the debris has entered the system then just changing the HPFP won’t solve the problem of blocked injectors due to the swarf in the fuel system... this is why HPFP failure is such a disaster.

Quote:

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Originally Posted by Crasher

IF the HPFP had eaten its internals AND the debris has entered the system then just changing the HPFP won’t solve the problem of blocked injectors due to the swarf in the fuel system... this is why HPFP failure is such a disaster.

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I’m almost certain this is not the case. The car has been idling rough for a long time and the HPFP hasn’t catastrophically failed. I just assumed that it could be faulty. The car starts and drives perfectly.

Also the injectors have been changed.

After driving the car briefly this evening, the idling has improved slightly but it’s still not right.

After looking up the fault code (P1065) it seems that there are a few possible causes. Haven’t checked the low pressure pump or the in-tank lift pump yet. It seems unlikely either of these could be the culprit, but I’m not sure.

Someone suggested doing a compression test. I doubt there is a mechanical problem as the engine drives so well. It’s literally just the idle that’s a problem.

We’ve also changed the fuel rail and the sensors at both ends to no avail.

Already spent around a grand trying to get this issue sorted so a little bit reluctant to keep throwing money down the drain unless I know exactly what needs doing.

Hi

Does anyone know if I should have done a software reset after changing the high pressure fuel pump?

Because I didn’t and now I’m wondering if this will make any difference.

Quote:

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Originally Posted by the surfer

I’m almost certain this is not the case. The car has been idling rough for a long time and the HPFP hasn’t catastrophically failed. I just assumed that it could be faulty. The car starts and drives perfectly.

Also the injectors have been changed.

After driving the car briefly this evening, the idling has improved slightly but it’s still not right.

After looking up the fault code (P1065) it seems that there are a few possible causes. Haven’t checked the low pressure pump or the in-tank lift pump yet. It seems unlikely either of these could be the culprit, but I’m not sure.

Someone suggested doing a compression test. I doubt there is a mechanical problem as the engine drives so well. It’s literally just the idle that’s a problem.

We’ve also changed the fuel rail and the sensors at both ends to no avail.

Already spent around a grand trying to get this issue sorted so a little bit reluctant to keep throwing money down the drain unless I know exactly what needs doing.

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This is a long shot in the grand scheme of things but my main guess on this. Check the loom for a rub through. Follow the wiring of the pressure sensor and the regulator which are either side of the fuel rail. Follow the wiring back as far you can with a small mirror so you can see the rear of the loom at all times. You might have to get underneath the front of the car for some of this (keep safety in mind)

I was just poking around my own car the other weak and saw my loom was out of place digging into a bracket, it reminded me of your fault