No vcds codes, but fuel economy is woefully bad. Getting around 450km from 45L of fuel (20ish mpg for imperial guys). Any ideas on what could be the cause. Injector values all within +/- 1.5%, dpf mass is no where near threshold. 

Yeah, not good!

More detail would be useful, so people know rather than assume.

 

Diesel or petrol (I 'assume' diesel), manual or auto, distance on odometer, ownership history including any fixes, servicing history, has consumption always been bad or a recent phenomenon, typical driving patterns, location in Aus (ie Brisbane is recognised as having the worst traffic conditions), how does the car drive???

 

Do for starters but others will probably seek more to try and help you.

 

Edited 31 January, 20251 yr by Gerrycan

Tdi is listed in the title mate. DSG. Mix of city and highway, rarely in stop/start traffic. 200k on the odo and been serviced every 10k since the beginning of its life. Going to delete dpf and egr shortly and see if there is any improvement but from all accounts via VCDS, there are no problems… 

3 hours ago, jaychen said:

Going to delete dpf and egr shortly

Good moves. Local taxi firms may know someone who can do an undetectable DPFectomy for you.

Instead of looking at dpf mass values see dpf pressure difference at idle and when giving gas while standing still on neutral. Google can tell acceptable values I dont recall them right now.

 

Does it use oil? Air filter ok? Boost pipe cracked? Brakes jammed?

 

How close the injection deviation values are to 1.5?

 

I believe also mk3 EGR can brake so that valve flap gets disconnected from the controllel so that the car thinks the egr is moving while it is not.

50 minutes ago, RattleWagon said:

Instead of looking at dpf mass values see dpf pressure difference at idle and when giving gas while standing still on neutral. Google can tell acceptable values I dont recall them right now.

 

Does it use oil? Air filter ok? Boost pipe cracked? Brakes jammed?

 

How close the injection deviation values are to 1.5?

 

I believe also mk3 EGR can brake so that valve flap gets disconnected from the controllel so that the car thinks the egr is moving while it is not.

Doesn’t use a any oil between changes. 
 

I did check pre and post pressure, negligible difference from memory. 
 

will try and pull the egr and do output test to see if it’s ****ed 

 

Will check values again tonight. 
 

thanks 

I'd fix the problem rather than mod your way around it at this stage.

On 31/01/2025 at 16:23, RattleWagon said:

Instead of looking at dpf mass values see dpf pressure difference at idle and when giving gas while standing still on neutral. Google can tell acceptable values I dont recall them right now.

 

Does it use oil? Air filter ok? Boost pipe cracked? Brakes jammed?

 

How close the injection deviation values are to 1.5?

 

I believe also mk3 EGR can brake so that valve flap gets disconnected from the controllel so that the car thinks the egr is moving while it is not.

injection values all within +/- 0.25 (3/4 were 0.05).

 

Air filter is new. Boost pipes all ok (pressure tested and would think there would be a pressure deviation code if cracked?), brakes all good. 

 

Soot mass measured is only 9g currently and was 10km since last regen.  

Couldn't find a dpf pressure deviation measuring block though, only DPF pressure sensor bank 1, 45hPa at idle.  Do you know the IDE code for pressure differential sensor on Mk3's or how to make sense of the pressure values? Is it a deviation from atmosphere (1000hPa) of 45hPa? Less than half a psi is next to nothing. 

 

Didn't get a chance to pull the EGR off yet, but will try this week. 

Never owned a diesel with DPF but I thought the problems with modern high mileage (km) diesels also occurred with high 'ash' levels? What does that register?

 

A very minor point but 10L/100km equates to 28.5 imperial mpg so not quite as awful as the title claim but obviously well below expectations.

Edited 2 February, 20251 yr by Gerrycan

1 hour ago, Gerrycan said:

problems with modern high mileage (km) diesels also occurred with high 'ash' levels? What does that register?

The particulate trap (DPF) is getting full (again).

5 hours ago, jaychen said:

injection values all within +/- 0.25 (3/4 were 0.05).

 

Air filter is new. Boost pipes all ok (pressure tested and would think there would be a pressure deviation code if cracked?), brakes all good. 

 

Soot mass measured is only 9g currently and was 10km since last regen.  

Couldn't find a dpf pressure deviation measuring block though, only DPF pressure sensor bank 1, 45hPa at idle.  Do you know the IDE code for pressure differential sensor on Mk3's or how to make sense of the pressure values? Is it a deviation from atmosphere (1000hPa) of 45hPa? Less than half a psi is next to nothing. 

 

Didn't get a chance to pull the EGR off yet, but will try this week. 

 

For me the dpf pressure difference is IDE07745. I believe ideal value / with new dpf after regen this should be below 10 hPa at idle. I think 100 hPa at idle is somewhat limit for bad dpf, especially after regen.

 

Yes i guess there would be code if enough boost leaks and turbo could not make enough to compensate the leak / meet the specified pressure value.

 

Injector values are great.

 

Have you considered seized brake caliper(s)?

6 hours ago, RattleWagon said:

 

For me the dpf pressure difference is IDE07745. I believe ideal value / with new dpf after regen this should be below 10 hPa at idle. I think 100 hPa at idle is somewhat limit for bad dpf, especially after regen.

 

Yes i guess there would be code if enough boost leaks and turbo could not make enough to compensate the leak / meet the specified pressure value.

 

Injector values are great.

 

Have you considered seized brake caliper(s)?

Check calipers/rotors mate, everything spins fine and is not locked up. 

I will have a look into the pressure sensor values and see if it returns anything worth noting.