Does Your VW TDI Diesel Engine Hiccup or Hesitate?
The VW diesel (TDI) engine is one tough engine capable of going 500,000 miles when maintained. However, it has its issues. The 2006-11 VW TDI models seem to have a common issue, as shown by complaints to NHTSA about hesitation and or a "hiccup", that is, a split second pause, usually when when accelerating.
Most of the time, the "hiccup" lasts a second but to a driver it is very noticeable, enough to cause an "aha" or "what's that" freak out. It can be sporadic or frequent. Some drivers become accustomed to it and the VW dealer will claim it is within normal specs. But the last thing you want when accelerating is a one-second pause or loss; it could happen at precisely the wrong time.
What is it?
There are a couple of possibilities to check out or tell your mechanic to check out.
- Excessive oil gathering near the lower end of the intercooler. Disconnect the lower hose of the intercooler with a container ready to catch any oil. There should NOT be more than 2 tablespoons of oil collected there. If there is, this could be an indication that your turbo seals are leaking. If there is much more than 2 tablespoons, consider a turbo replacement.
- Your EGR, which recirculates exhaust gas back into the intake manifold (pre-turbo), could be getting clogged with soot from diesel. It does happen. It could also have some water droplets (not good). Disconnect the EGR and inspect inside for excessive soot, and clean it out.
- You may need to update your computer software for the car at the dealer, if available. The software the engine uses regulates the EGR valves opening and closing. VW knows it is not perfect software, and small gaps appear as valves open and close. In some cases, when new software was downloaded, the hiccup went away, in other cases, the update did nothing.
The slight hiccup is mostly likely one or all of the three above. The hiccup is not usually a serious issue and is more of a nuisance. Drivers with a DSG tranny in the low gears may have it also, but in that case it is simply due to the split-second timing between gears. Diesel engines are different than gas engines.
If the hiccup is due to soot, you can try the following to try to remedy it:
- Go up a hill or straight stretch at 3-4000 rpm for a sustained time to blow out and remove soot from any gathering points.
- After the engine is warm, when getting on a road, accelerate quickly through 2000 RPM to blow out soot.
Some think the hiccup is caused by the turbo: it isn't. If the turbo stops, you will have tons of black smoke and your car will limp or stop functioning.
Oil Side Note: VW Diesels require special oil to be used to prevent rapid cam wear. If you are unable to find the special oil, a perfectly good oil is any synthetic brand with a API rating of CJ-4 or CI-4, which is easier to find.