Hesitation under light throttle, has anyone experienced this?

[Rod_H]

It happens for me at any speed above 50km/h under light acceleration, most evident around 65-70 in 4th.

Mine does it too, just like the car above..
had it back to VW and they replaced a few seals, they reckon in the inlet system, it still does it, but not as much.
I noticed it at around the 20000k mark. Car has done 35000k now. must be an idiosyncrasy of this motor!
Just make some soot and it goes away

[bluey]

TDI Club FAQ section 8q mentions sticky EGR valve as possible cause of hesitation. It also suggests a preventive fix to recalibrate the engine management to allow more air which reduces the sticky soot buildup. It also says that driving at that engine speed is "improper use of the transmission".

[Rebuild]

new to this, but,
faulty MAF sensor? any codes?

[Jaymz]

new to this, but,
faulty MAF sensor? any codes?

No, its not that serious. Its a hesitation not a fault

[Greg Roles]

Any hesitation in acceleration is a fault!

[bluey]

Article on cleaning carbon from TDI intake systems - looks easy enough to have a peek in the intake.....

[Greg Roles]

Possible, but unlikely in cars that have only done about 20k's.

Still, can't recommend the Provent enough, I drain off about 100mL of oil every two months or so, and still, some, is getting through into the turbo. hate to think what's happening stock...

[Logzy]

Possible, but unlikely in cars that have only done about 20k's.

Still, can't recommend the Provent enough, I drain off about 100mL of oil every two months or so, and still, some, is getting through into the turbo. hate to think what's happening stock...

Interesting that you have to drain about 100ml every 2 weeks.
Do you also have to top up the engine oil? Does that level move?

[bluey]

So that 100mL of oil or diesel or a mix??? I thought CCV is meant to get rid mostly of blow-by gases which includes an element of fuel which is not good for the oil.

[Jaymz]

Article on cleaning carbon from TDI intake systems - looks easy enough to have a peek in the intake.....

Good find bluey. I like DIY articles like this.

Have to agree with cogdoc though, still only have 11k's on it.

What's interesting though is i've put a tank of ultimate in it and been driving for the last week and the hesitation has almost gone. It doesnt do it at all at speed only just off the idle now.

[gerhard]

Article on cleaning carbon from TDI intake systems - looks easy enough to have a peek in the intake.....

It's interesting that US model VW diesels can have "dirty EGR" problems - I have a Jackaroo with 150,000ks and the EGR valve/porting is clean as a whistle, whereas the same engine in US vehicles has had endless problems with fouling of EGR valves and galleries. I know this is a petrol, and the article is about diesel VWs, but I wonder if there is something about US fuel or engine oils which contribute to this being a problem there but not here?

[bluey]

[...] I wonder if there is something about US fuel or engine oils which contribute to this being a problem there but not here?

I suspect the clogging may have to do with the sooting problem of low cetane fuels in USA. End of first post in this thread mentions typical cetane ranging from 40-51! (40 from refinery + additive to improve cetane). We (and I think europe) have minimum standard cetane 46. VW recommends higher (49-51) according to brochures, depending on model. Apparently in the USA the low sulphur diesel is better for preventing sooting.

(Petrol should not have the same problem, as crankcase gases include petrol fumes which do not mix with carbon particles to make sludge.)

Found some interesting documents on 1.9 TDI design.

[Greg Roles]

Remember though, that blowby is an element of compression in the crank, and that any fuel / combustion mix entering the crank past the rings is going to do it a LOT more at the typical 18:1 diesel compression numbers.

All I know is I'm getting black, black oil out of my Provent on an alarming basis, and yet there is still a little oil just prior to my turbo each time i pull the inlet off.

[bluey]

If Jaymz has fixed it with Ultimate, doesn't that suggest injector deposits??

100mL every couple of months is say 500-600mL per year. How does that compare to the oil usage rate? Would be interesting to see a used oil analysis from the Provent drain.

[Greg Roles]

If Jaymz has fixed it with Ultimate, doesn't that suggest injector deposits??

100mL every couple of months is say 500-600mL per year. How does that compare to the oil usage rate? Would be interesting to see a used oil analysis from the Provent drain.

I'm only guessing on the volumes, as each drain of the provent covers the bottom of a typical 5L oil drain pan, and it's set up as a catch system only, so when it totally fills, it drips out onto the ground, when I notice and drain it. I could be losing a fair bit until I notice.

All I can say is there is a heck of a lot of oil blowby, even given the TDI's very intricate and complex oil seperation system in the tappet cover. It even has a cyclonic centrifuge type chamber, really clever stuff!

My TDI seems to use very little oil between services every 7500k's, so per year it can't be much, but i'd prefer that isn't going through my inlet, and especially not mixing with the EGR gas to make the horrible sludge outlined above. This means the black manifold, inlet ports and even valves are getting a nice sludge coating, way before any ultimate cleaners are injected into the cylinder itself.