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2004 Audi A3 – 2.0 TDi – Ruff idle and cutting out under acceleration

Audi A3 2.0TDI 2004

Problems:  Poor idle and cutting out under acceleration


The car was recovered to us, first thing we did was a full scan – this revealed no fault codes in the engine but many in other ECU’s.

We then inspected the engine, some signs off poor workman ship but everything was in place a quick road test showed the fault with it cutting out under acceleration (I noted that misfire started before the cutting out and it also could be delayed by easing off the throttle).  Once the car cut out it took a long time to restart with a slow building of cylinders firing before restart.  I managed to get the car to cut out and coast back into the workshop with the car in the non start stage. With a crank over and an external fuel supply into the inlet the car started straight away.

Another quick test driver was done to place the car into a non running state and I removed the top off the fuel filter this showed the fuel filter housing was full off fuel, just to confirm the electric pump delivery amount was checked and this provided the correct amount off fuel.   With the filter reassembled, I tired re-starting the car a short crank showed no sign off a restart. We next place a fuel pressure gauge into the tandem pump.  This showed a slow to build fuel pressure and on idle the pressure was only about 3 Bar on the test drive the fuel pressure would rise to 10bar (10Bar @ 4000RPM is correct) then tail off as the car would starting missing and then drop down to under 4 bar and the car would cut out.

Fuel pressure port

After a quick chat with the customer he informed us the injectors had been reconditioned only a month ago.   Taking that the injectors were correct this left the fuel rail in the cylinder head or the tandem pump.  The customer supplied us a 2nd hand tandem pump, this was fitted on and the car was road tested.   On the road test the same conditions appeared,  we reconnected the fuel pressure gauge and this showed the same readings as previous tandem pump. (As the pressure readings were identical on the old and the 2nd hand one, we either had the same problem with both pumps or something else was wrong)

The customer gave us authorisation to remove the cam cover and inspect the injectors and cylinder head.   With the cover removed the fault was clearly visible, 6 out off the 8 injector hold down bolts were snapped! The cylinder head show some slight signs are wear but looked ok,  new injector seals were fitted and correctly torqued down.

injector and snapped bolts



Slight damage to injector bore

The the injector rocker shafts were installed and correctly set-up. With everything back together the car was road tested and performed correctly and all fault codes were cleared.

Injector rockers being setup

Toby started work at DG Motor Services in 1996, in this time I have seen a major change in the amount of electrical systems used in today’s modern vehicles. With my electrical and mechanical hobbies helping me stay in touch with today’s modern technologies

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