2.0 TDi 140 cold start issues and general running queries

[AndyMartin]

Hiya guys new here so be gentle please
Ive got a 2.0 TDi 140 A6 which doesn't feel right.
If started from cold when being stood overnight it coughs into life, with a misfire for the first 3-5 seconds.
Then when you set off, under load if you plant the accelerator the car picks up slowly like its being deprived of fuel, very flat but it doesnt kangaroo, its just like your barely touching the accelerator. After a minute or so this clears up and its fine.
When warm it runs better but it seems a bit flat in the higher gears under load, the fuel economy doesnt seem the best (about 40mpg) and seems flat when pulling away in 1st unless you press the pedal further down.

I was thinking injectors after having a mondeo tdci but don't know what these are like for injectors. I was going to check the injection loom by measuring the pin resistances on the connector but have no idea of the pinout.

When i first got it, it had a misfire when warm on idle - the torsion was at -3.7 so i cracked both centre bolts of the cam pulleys round a bit clockwise and its now at 0 and runs smoother on idle.
Is there anything I could check? I tried doing basic setting in VCDS for EGR and the engine speeds up to about 1500rpm when you turn EGR off, but I didnt really understand what I was doing.

Im competent in electronics but never owned an VAG before so its all new to me.



Cheers
Andy

[coolraj003]

I couldnt help you with the misfire issues with the engine but i can tell you that the engine feeling a bit flat in the first gear is normal. I felt it a bit slow as well thinking that there has to be some problems with the engine that its seems flat but turns out its the engine itself which limits the torque in first gear to avoid any abuse. Try to contact more experienced members like A8tech as they will be able to explain your issue better and help you resolve it. good luck

Raj

[a8 tech]

Hiya guys new here so be gentle please
Ive got a 2.0 TDi 140 A6 which doesn't feel right.
If started from cold when being stood overnight it coughs into life, with a misfire for the first 3-5 seconds.
Then when you set off, under load if you plant the accelerator the car picks up slowly like its being deprived of fuel, very flat but it doesnt kangaroo, its just like your barely touching the accelerator. After a minute or so this clears up and its fine.
When warm it runs better but it seems a bit flat in the higher gears under load, the fuel economy doesnt seem the best (about 40mpg) and seems flat when pulling away in 1st unless you press the pedal further down.

I was thinking injectors after having a mondeo tdci but don't know what these are like for injectors. I was going to check the injection loom by measuring the pin resistances on the connector but have no idea of the pinout.

When i first got it, it had a misfire when warm on idle - the torsion was at -3.7 so i cracked both centre bolts of the cam pulleys round a bit clockwise and its now at 0 and runs smoother on idle.
Is there anything I could check? I tried doing basic setting in VCDS for EGR and the engine speeds up to about 1500rpm when you turn EGR off, but I didnt really understand what I was doing.

Im competent in electronics but never owned an VAG before so its all new to me.



Cheers
Andy

pm answered

[AndyMartin]

OK Guys heres some further info.
It turns out that I had adjusted the timing too far, and the 0 torsion reading was out of range. I have now got it back to 0.5 and drops to 0 when accelerating which is apparently correct.

I have made some observations..

The ECU gets the torsion value from the intake cam, the exhaust cam does NOT change the torsion value.
However its the exhaust cam which adjusts injection timing, and adjusting this retards / advances the injection or however it works.

The biggest issue I face now is getting the exhaust cam correctly set. I have played about with it and observed the following...

Turning the centre bolt anti clockwise (retarded timing) makes the car hesistant around 1000rpm and the car dies when pulling away. However you get 0.2l/h fuel consumption here, and the injection quality looks to be better.
Advancing the timing slightly removes the hesitation, and the car pulls strongly low down, if a little flat top end.
Advancing it into a sweet spot seems to give a good balance of low down torque and top end power, however the idle is lumpy.
Advancing it further clears the lumpy idle and the bottom end starts to feel flatter, whereas there seems to be a bit more top end. Also the fuel consumption starts to rise to 0.4 - 0.6l/h, injection quality also goes all the way up to 2.3 for inj 3

This is just by moving the exhaust cam, and leaving the intake cam set so the torsion is 0.5

The problem I have is I cannot easilly get at the crank pulley to check markings, and im loathed to strip the front of the car down.
When I bought the car it had the lumpy idle, which is the reason I'm at this stage now.

Can anyone tell me what idle consumption should be? I was aiming for 0.2l/h but in achieving this I seem to get a lumpy idle.
I prefer the engine now in that it pulls stronger lower down and seems to need less work to make it move.

I will drive it over the next few days and see what consumption i achieve on both the DIS and calculated.
I will also see if my cold start problem improves.

[smithen999]

Hi there, I'm having similar problems following a Cambelt change at a specialists. Can I just ask which measuring block to use to check the torsion value? would I check the value at idle?

Cheers
Rich

[a8 tech]

Measured values 04 in address 01 look at zone 4

Example below incorrect valve timing after cam belt install, check at normal operating temp and at idle speed only

1 880 /min
2 5.0 °n.OT
3 4.0 °KW
4 6.34 ° THIS MUST BE AROUND 2.5 FOR CORRECT VALVE TIMING


004 Activation of pump/nozzle unit piezo valves
Coolant temperature min. 75°C:

1) Engine speed
At idle: 870 ... 890 rpm
At full throttle: 2800 ... 3200 rpm

2) Specified commencement of injection
At idle: 4.2 °b.TDC ... 5.2 ° aft.TDC
At full throttle: 5... 18 °b.TDC

3) Specified duration of delivery
At idle: 2 ... 9 °CA
At full throttle: 20 ... 30 °CA

4) Rotation angle
Idle/full throttle: -6 ... 6 °CA

[AndyMartin]

If I advance the exhaust cam it cures the lumpy idle and you can feel the car is more lively in the higher rev range. However it is heavier on fuel like this, im struggling to get 37mpg combined.
If I the exhaust cam the car idles lumpy, however it is slightly better on fuel.

In the injection quantity blocks, injector 3 doesnt seem right in that it heads up towards 2.99 unless the timing is retarded enough. 2 and 4 seem consistant at about 0.6, with 1 going the other way due to number 3.
Ive read about possible cracked heads, and injector seals but thats a last resort really. It idles fine if the timing is advanced enough. However I don't know if i should move the inlet cam as well. At the moment ive set the inlet cam so it gives a torsion of 0.5KW. As its the inlet cam that the car gets the torsion value from.

Can you assist? Are the 2.0 tdi 140 heavy on fuel anyway?

[joshA6]

. However it is heavier on fuel like this, im struggling to get 37mpg combined.
If I the exhaust cam the car idles lumpy, however it is slightly better on fuel.


Can you assist? Are the 2.0 tdi 140 heavy on fuel anyway?

I have to say, 37 combined is about right. I have had mine for 30k and it has never achieved anything better than that. The tank MPG matches that given by the computer, so I know the computer is spot on.

I found chipping the 140 made it miles better to drive, and the fuel economy stayed the same.

[AndyMartin]

Thanks for that, all the diesels Ive owned in the past have never done less than 42mpg so this took some getting used to, I was worrying that it was poor on fuel but as long as it is doing as it should then I'm happy. I find my fuel computer reads a bit higher than calculated (i used the one which resets every trip) I suppose the A6 is a big car to pull along, it is better on fuel if you keep it sat at 60 for a long journey.

[smithen999]

Thanks for the info, will have a play on Thursday and will report my findings back for comparison. On the fuel consumption note, mine averages a steady 37 combined - albeit it's a 170 A4.
37ish from an A6 140 sounds fairly reasonable though would have expected around 40