[jond9001]

I'm not sure if there are already posts on this matter, but I am becoming concerned about a strange stutter that my car is making while in motion. The stutter happened once about a month ago, and since then it has happened twice in the past week.

The stutter is hard to explain. While cruising along (not during hard acceleration), the car engine will stutter twice, and then remain running normally afterward. When this happens, it seems as though the engine cuts out for a fraction of a second, and two times, and then the car runs as if nothing happened. I am becoming concerned about this because it has happened twice in the past week.

I have read about the lift pumps commonly failing in these cars, but I do not know if this would be the same issue. About two weeks ago I had the car diagnosed with vag-com software, and there were no faults with the fuel system (from the scans that I received). Has anybody had a lift-pump fail? If so, are there any tell-tale signs of a failing lift pump?

Any thoughts on the matter would be appreciated!

Jon

 

[chittychittybangbang]

The way to diagnose a bad lift pump would be to remove the feed line and put it into a bucket, then apply 12v to the wiring. If it runs it's good.

Yes they can fail and some models will let you continue running if they fail, some will cause fuel starvation if they fail.

Here are instructions on how to manually run the pump without vag-com (it sounds like someone local scanned it for you) and with vag-com *new name is VCDS. http://www.myturbodiesel.com/1000q/a5/2009-2010-VW-TDI-fuel-filter.htm It's for the 2009+ engines but the lift pump part is the same.

Don't know the cause of the intermittent stutter other than maybe an electrical fault. If it were a flywheel problem you'd have other symptoms and if it were something like bad wiring at the injector harness it should show up in a scan. If it were worn camshaft it'd be noticeable at idle and constant.

Some suggestions: have the cam timing checked: http://www.myturbodiesel.com/1000q/multi/PD-adjust-Idle-TDI.htm, maybe it's at the edge of the range and the electronics can compensate most of the time. Just a wild guess. It could also be EGR gasses causing some temporary running problem, maybe the intake valve (like a throttle) gears are stripped and hitting a wear spot as they move.

Overall miles?

 

[jond9001]

Chitty

The car hasn't stuttered in a long time now, so I am becoming less and less concerned about it. I do have a new concern, however, which is becoming more and more evident (or I am just very aware). The problem is that the car (especially when cold) will be building boost, but the engine is not accelerating as fast as it should be given the amount of boost it is building. The car will then jolt and take off suddenly, most of the times with a nice puff of smoke from the tailpipe (telling me that the car was fueling for the amount of boost it was building, but that things weren't running very efficiently).

I know a man who had an issue with his EGR system leaking air, and it affected the anti-shutter valve in some way. This person said his car would act like it had very little power, and then jolt to life. He also said he had a hissing noise coming from behind the dashboard. He had the issue fixed, and said the car is back to normal. When I asked what exactly they fixed he didn't seem to know the details. I know I have read something about EGR leaks on this site, but I can't seem to find the article now.

Do you have any information on this issue? If you could put the link to the EGR system problem in a reply, I would really appreciate it.

 

[chittychittybangbang]

It's possible you do have an EGR leak. This is the exhaust gas recirculation from the turbo to the intake. If there's a leak you should see soot since it's dirty air. I think this was a dealer recall item but not sure, you could check. Veyr common problem.