Loss of boost on 110TDi (Revo)

[Gyp]

After not being on Briskoda for *ages*, I come back and it all looks different. Oooo.

Anyway, I had an odity this morning; under gentle acceleration I lost all boost. Car continued to run nicely/quietly/smoothly, but in a very low performance way. Having stopped and restarted the engine, all is well again. I've got 94k on the clock, I've been running a Revo remap for the last 30k miles or so, and at the moment it's running on about 60% biodiesel (ok, Tesco sunflower oil), 40% pump diesel. The car is generally driven quite hard, so the turbo's usually boosting quite well. Perhaps it's not used to gentle acceleration ;-)

One oddity that's probably worth mentioning as it might be relevant is that recently I've noticed a little whif of exhaust smell in the car on start up.

I've switched the map back to stock and will take it out and give it a good run today.

I've got the shareware VAG-COM but won't get a chance to get it to the car until later in the week, but it seems like the turbo just switched off (surely it's mechanical - can it do that?)

Any thoughts?

[mbames]

Sounds like limp home mode, vag-com will probably flag up an overboost fault code. Cycling the ignition is the cure. Clear the fault, and see it comes back next time the car becomes sluggish.

Mine does this most days, and I assume that mine is caused by sticking vanes in VNT mechanism in the turbo. If yours is regularly driven hard, then something else may be the cause. A failing coolant sensor, n75 valve (controls the VNT mechanism by applying a vacuum), or even the MAF coulkd possibly cause this issue.

[dent doc]

This is a common problem. Its uasually caused by the maf sensor being on the way out. Ive seen this a good few times and it will only show an over boost problem when ran on VAG-COM

[mbames]

Mine normally "kangeroos" down the road in 2nd and 3rd gear around the 2,500-3,000 rpm mark when I leave work in the afternoon, and then has no boost (some times it kangeroos a bit and then is ok, but that is rare!). I have always assumed that is a sticky VNT, but do you think it might be the MAF? Normally I cycle the ignition shortly after that it seems to then normally remain ok for the remainder of the 60 miles to get home. Sometimes it does it again - most noticably, when I was booting it up a hill to overtake a slower moving car, and it went to into limp mode

[Gyp]

Well, since restarting I've gone about 100 miles down country lanes with lots of traction-control-bothering hill work with no problem. I've got the Revo map back on, and lots of boost and no more problems to report. I'll have to see how it goes.

[smileonimpact]

Hi there,

My 110Tdi does exactly the same about once every 3-4months, same cure with the ignition. I have full vag-com (vcds) and it has never registered a fault for this! I have checked every time.

I was thinking MAF sensor as I've had this go on a previous 110Tdi and the symptom was identical although permanent loss of power, (I was being overtaken by vintage lorries whilst going up hill, no power at all)

smile

[Gyp]

My 110Tdi does exactly the same about once every 3-4months, same cure with the ignition. I have full vag-com (vcds) and it has never registered a fault for this! I have checked every time.

I was thinking MAF sensor as I've had this go on a previous 110Tdi and the symptom was identical although permanent loss of power, (I was being overtaken by vintage lorries whilst going up hill, no power at all)

Well,this is the first time in 95k miles, so if it only happens that often I'll not be upset. That said, the fact that it happened at all is a worry and something that might make me twitchy if I'm going for an overtake.

Ah well, I'll pop some proper fuel in and thrash it for a while and see what happens.

[Gyp]

Did it again yesterday, conspicuously within about 1/4 mile of where it happened last time; at place I rarely visit. Perhaps the car's developed an allergy to Gloucester

[mbames]

Did it again yesterday, conspicuously within about 1/4 mile of where it happened last time; at place I rarely visit. Perhaps the car's developed an allergy to Gloucester

Mine has to go up there for work in a week or so for work, so I'll see if mine is extra naughty up there!