1.0 gal/hour idling problem .... Help please?! Z30DT

[babybluemaxer]

Hello Guys,

Recently after swapping the fuel filter - genuine gm (Maybe the problem?) after running it for a journey .... i park up & the car is idling at 1.0/1.1 gal/hour.

Usually on start up from cold it idles at 0.4 then goes down to 0.2.

This issue has only appeared recently after a 170 mile to & from Bristol!

Can anyone help or have any idea's as to why it's doing this?

Is this a common thing when you change the fuel filter for a genuine one?

Or could this link in with the knocking sound from cold?

Many thanks,
Glenn.

[cont1204]

Could just be a DPF regen although it shouldn't be doing it when the engine is cold. Strange one that.

[babybluemaxer]

Could just be a DPF regen although it shouldn't be doing it when the engine is cold. Strange one that.

Hello mate,

This was after a 4 mile journey each way this morning but the engine was at 80 degree's, then shot up to 90 degree's once i pulled up & started idling at 1.0/1.1 gal/hour?

Would that explain anything?

[m8internet]

Have the idle revs changed?

[Critch]

Get dpf saturation looked at

[babybluemaxer]

Have the idle revs changed?

I've noticed since fitting the gm fuel filter when warming up from cold, the revs are constantly at 700ish rpm but before the change, it used to start at around 950rpm & go down as it sat idling for a minute or 2!

Get dpf saturation looked at

Where would i need to go to get this done? Possible knackered dpf?
Symptoms have only started since changing the fuel filter?

[ph67]

Does it do this everytime after cold start or a few miles?

Take it for another long run and do 50 miles plus when the symptoms start - that should take it out of the usual distance covered to carry out a DPF re-gen easily - the symptoms you state (1.0gal on tickover, increased water temp etc) are usual for DPF re-gen - you can also tell if it's doing it when driving if you lift of the throttle and coast down a hill in gear - normally consumption will go to about 313 or 353 miles per gallon when DPF re-gen is running or 999 miles when it's not. Providing it's carried out a full cycle - i.e. re-gen started on it's own and you've driven it for 25 mins or so and it'c ompleted the cycle - it will then revert back to normal. If it then shows the symptoms again when you use it next time or whilst on the same drive I'd say the DPF is blocked or you've got a problem with the fuel mix/burn as it;s not burning the fuel cleanly and blocking the DPF too quickly.

[babybluemaxer]

Does it do this everytime after cold start or a few miles?

Take it for another long run and do 50 miles plus when the symptoms start - that should take it out of the usual distance covered to carry out a DPF re-gen easily - the symptoms you state (1.0gal on tickover, increased water temp etc) are usual for DPF re-gen - you can also tell if it's doing it when driving if you lift of the throttle and coast down a hill in gear - normally consumption will go to about 313 or 353 miles per gallon when DPF re-gen is running or 999 miles when it's not. Providing it's carried out a full cycle - i.e. re-gen started on it's own and you've driven it for 25 mins or so and it'c ompleted the cycle - it will then revert back to normal. If it then shows the symptoms again when you use it next time or whilst on the same drive I'd say the DPF is blocked or you've got a problem with the fuel mix/burn as it;s not burning the fuel cleanly and blocking the DPF too quickly.

No, i've never noticed it apart from the 2 times mentioned above.
It's happened after a drive to bristol & back - 160 mile trip.
It also happened this morning after a 4 mile driving each way?

How & when should the dpf re-gen start? Can i force a re-gen?

[m8internet]

I've noticed since fitting the gm fuel filter when warming up from cold, the revs are constantly at 700ish rpm but before the change, it used to start at around 950rpm & go down as it sat idling for a minute or 2

That sounds correct
The cold idle is just under 1000rpm, the warm idle is between 600 and 800rpm
Once the engine temperature has reached about 55'C it should reset the cold idle (sometimes with what feels like a bump)
However, as with all diesel engines it should not be left to idle from cold and should be driven straight away (limited to 3000rpm)

Equally, with DPF activated the engine is assumed to be warm
There should be a warning light for this, and the engine should not be switched off once activated and only switched off once the cycle has completed
It sounds like it did not complete and the EMS has become stuck
As above, once the engine has warmed up take it for a high rev run at about 50mph (say 3rd or 4th gear) for about 5 or 6 minutes
This should be sufficient to get high temperature gasses through both sensors and reset the cycle

[babybluemaxer]

You can buy a DPF cleaner that you add to the fuel tank, when a DPF is regenerating you'll smell it from the exhaust, like a burning plastic/rubber smell and you might hear the exhaust hissing a little.

I think some people say you can trick the car into a DPF Regen by having the Rev's above 2k for 20 minutes...

I've got a decent drive to Devon tomorrow so i will make sure i do this.
Thank you very much!

That sounds correct
The cold idle is just under 1000rpm, the warm idle is between 600 and 800rpm
Once the engine temperature has reached about 55'C it should reset the cold idle (sometimes with what feels like a bump)
However, as with all diesel engines it should not be left to idle from cold and should be driven straight away (limited to 3000rpm)

Equally, with DPF activated the engine is assumed to be warm
There should be a warning light for this, and the engine should not be switched off once activated and only switched off once the cycle has completed
It sounds like it did not complete and the EMS has become stuck
As above, once the engine has warmed up take it for a high rev run at about 50mph (say 3rd or 4th gear) for about 5 or 6 minutes
This should be sufficient to get high temperature gasses through both sensors and reset the cycle

Thank you very much for all your help.

I will do this tomorrow as i have a long drive to devon!
I'm going to try get some dpf cleaner & put some redex in the tank again.

Appreciate everybody's help on this matter.