From a VW engine tuning site: "The 1.9 TDi was used in a wide variety of cars from the VAG group and came in different power levels. All had BOSCH injectors, and Bosch ECU's which are really sturdy and very protective of the engine. For my diesels, both IDI and TDI, which I have re-ringed (never needed pistons), I would not idle the car much, but rather drive it fairly hard, and try to avoid extended times of lower power settings. I would consider a two pronged approach: 1. Review breakin instructions, and 2. compression check and leakdown check the engine on each cylinder. Have a 1.9 TDI Passat with the same issue and turned out to be the thermostat. I will point out that the ECUs in 1.9 TDI's have temperature dependent SOI (Start of Injection) maps. This is in order to protect the engine whe WE CAN UNDERTAKE ENGINE CONVERSIONS AS WELL AS BRAKE UPGRADES. WE REGULARLY INSTALL 1.9 TDI AFN CONVERSIONS USING ULTIMATE ENGINEERING COMPONENTS. FROM £6,950.00 FULLY INSTALLED. GOLF GTI 2.0 (AGG) ENGINES. FROM £4,500.00 FULLY INSTALLED. VW / AUDI 2.5 V6 TDI (MID MOUNTED) TIPTRONIC TRANSMISSION. ONE OF OUR OWN PROJECT VEHICLES. I think it's to do with the 1 bar atmospheric, you need to add that in the mix so the sensor needs to be capable. Safe max is about 21.5psi for the VA which is about 1.5bar so add the atmospheric and you're at the 2.5 but the 2.5 can actually read higher than 2.5 so it works. Volkswagen 1.4 TDI. VW’s most popular small diesel engine, the 1.9 TDI, has three cylinders and is fitted to a smaller model older than the Volkswagen Group. This engine is also installed on the Audi A2, Škoda Fabia and Seat Ibiza. The advantage is very low operating costs, but also has one serious technical drawback. Unlike the 1.9 TDI, the 2.0 TDI is plagued with a laundry list of potential problems, including the oil pump, the injectors, and the dual mass flywheel. If you can live with the lower power output of the 1.9, the 2.0 is best avoided. Meaning the entire bottom end of every 1.9 TDI is almost swappable with each other. We haven't tested this yet so don't quote me. But it would seem from initial inspection that every 1.9 TDI bottom end is practically the same. And for the two point oh, all they changed was the bore. EKvzV.