Acceleration cutting out under throttle

[Misla007]

Hi,

I own a 07' Golf TDi 103kw, recently any trip on the freeway where there may be acceleration, the revs and throttle decide to cut out, though not to the point of stalling, though instead trying to remain at a speed of 100km/h requires being in either 3rd or 4th gear.

instances when this has happened:

-from standstill entering the freeway and accelerating to approx. 120km/h
-climbing a hill in 6th gear
-overtaking by changing to 4th or 5th gear

I have also rolled down a hill on the free way in Neutral and then placed it back in 5th and this has also caused it.

Bear in mind this only happens at high speeds.

What the experts say:

I changed the valve which collects the crap last week.....didnt change anything.
VW says could be the turbo, though its accelerating fine anyother time.
Another mechanic says could be either the clutch slipping or the flywheel.

the exhaust light has now been on for over a 10 days.

any news....please help!

[parso_rex]

Have you had anyone scan it with Vagcom or similar yet ? . I can do it for you if you get stuck, only takes a couple of minutes and costs a flat white or Latte'. Once you have that info you can post it up for the Diesel experts to dissect. I have a couple of ideas though and I'm sure greg or one of the others will chime in shortly
Its not a clutch though thats a very weird thing to suggest. If it was worn the revs would rise as the plate slips under load.

Mark

[Russ59]

I just had a browse on some of the other forums and a similar issue was fixed with a fuel filter replacement, not saying this is your problem but it is a possibility, you don't mention how many k's you have on it, you could try a good quality diesel injector cleaner as well and see if that helps. I agree with parso_rex regarding the clutch, that sounds most unlikely from the symptoms. I'd be thinking more along the lines of a fuel issue, perhaps injectors ? It could even be a vacuum leak, loose or split hose .....? Good luck with it

[Greg Roles]

Mmm good call Russ, as a diesel is throttled by fuel, and the problem is only happening at high throttle demand ( ie high fuel required ) sounds like it's starving. A fuel filter is a cheap thing to replace, and like Russ so correctly suggests, a good fuel cleaner like Fuel doctor from supercheap would be a GREAT idea, AFTER the fuel filter element of course, no point in wasting cleaner on a possibly dirty filter.

There's also a "throttle flap" of sorts below the EGR valve that can gum up and as it does actually close off the airflow to assist the introduction of EGR, it could be getting stuck 3/4 open and stopping you getting full throttle. That and the EGR valve are the two moving parts that can get stuffed up by the oil gunk blowby, and it would be worth getting it cleaned or cleaning it yourself - look for Scotty's thread on that.

[gregozedobe]

A constantly on exhaust light points to DPF issues (which may actually be a faulty sensor, VW exhaust sensors have a well-deserved reputation for being unreliable). VW DPFs don't seem to cope with being driven in heavy traffic much of the time. Does that apply to your car ?

parso_rex's suggestion of a scan for faults will help narrow down the likely source/s of the problem.

Is it going into "limp-home" mode ? Symptoms are drastically reduced power, but resets itself when the engine is switched off and then restarted.

If so one cause could be sticky vanes on the turbo causing an overboost, the ECU recognises this and protects the engine by going into limp-home mode. Typically this happens with TDIs that are normally driven quite consrvatively with the revs usually below 2,000rpm. If the engine is given a lot of accelerator pedal (eg changing down a gear to overtake or rip up a hill) then the vanes are supposed to change angle at about 1,800 to 2,00rpm to keep the boost at the proper amount. If the vanes are stuck in the "low-rev/max boost" position they can't move to adjust the boost and then the ECU intervenes as described above.

Fuel problems are another possible cause, these can be caused by partially blocked filters, problems with fuel pumps/lines, PD units and injectors. I have even read of severely worn PD cams causing trouble (but this is pretty rare).

Like the others, I am a bit skeptical of a clutch/flywheel being a cause of the symptoms you described.

[REGS12]

Being an ex wheat cocky, sounds like a blocked fuel filter to me. That's where I would start. Don't get in to the expensive stuff until you've tried all of the cheap solutions.

[Russ59]

A constantly on exhaust light points to DPF issues (which may actually be a faulty sensor, VW exhaust sensors have a well-deserved reputation for being unreliable). VW DPFs don't seem to cope with being driven in heavy traffic much of the time. Does that apply to your car ?

parso_rex's suggestion of a scan for faults will help narrow down the likely source/s of the problem.

Is it going into "limp-home" mode ? Symptoms are drastically reduced power, but resets itself when the engine is switched off and then restarted.

If so one cause could be sticky vanes on the turbo causing an overboost, the ECU recognises this and protects the engine by going into limp-home mode. Typically this happens with TDIs that are normally driven quite consrvatively with the revs usually below 2,000rpm. If the engine is given a lot of accelerator pedal (eg changing down a gear to overtake or rip up a hill) then the vanes are supposed to change angle at about 1,800 to 2,00rpm to keep the boost at the proper amount. If the vanes are stuck in the "low-rev/max boost" position they can't move to adjust the boost and then the ECU intervenes as described above.

Fuel problems are another possible cause, these can be caused by partially blocked filters, problems with fuel pumps/lines, PD units and injectors. I have even read of severely worn PD cams causing trouble (but this is pretty rare).

Like the others, I am a bit skeptical of a clutch/flywheel being a cause of the symptoms you described.

It's a 2007 model 103 TDI so it's not fitted with a DPF or I would have considered that a possible cause as well. It could have a sensor problem too but I wouldn't think that would be causing the cutting out issue at higher speeds, but hey anything is possible with all this new hi tech so - called environmentally friendly crap

[mikinoz]

I agree with the above but will add - Faulty EGR?

[parso_rex]

I dont think the original poster has been back to look at his thread yet
.