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Audi A3 1.9 TDi Warm Engine Start Difficulty: Non-Closing Valves?

Pablo2828 122811 38
Best answers

Why is an Audi A3 1.9 TDI difficult to start when warm even though diagnostics show normal engine parameters?

The problem is more likely insufficient cranking speed or too small a warm-start fuel dose than non-closing valves: first check cylinder compression, then battery condition, starter speed, starter cables and grounds, and only then the fuel system and starting maps [#12554555] [#12585235] [#16828752] If the engine does not reach the RPM expected by the ECU during cranking, the controller gives little or no fuel dose, so a weak starter or poor power supply can cause long warm starts [#12585235] [#16828752] Several posters say the start dose can be adjusted with VAG-COM/VCDS (login 12233, adaptation channel 05), but this is a workaround, not a substitute for fixing the underlying cause [#12580120] If the mechanical and electrical checks are OK, have a specialist inspect the start maps and the fuel system rather than immediately assuming valve leakage [#12554714] [#12602284]
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  • #31 16910953
    miler80
    Level 34  
    majuDJ wrote:
    My friend changed slightly fuel doses with VCDS and it burns from the arrow on the warm one. Experts for this service in Warsaw count from 150-450 PLN !!!!

    Until you take the clamp off the battery.
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  • #32 16912440
    majuDJ
    Level 10  
    The battery has already been detachable and everything is ok.
  • #33 17070415
    djn1tr0
    Level 8  
    Hello, I would like to know exactly how the change in the starting fuel doses in VCDs looks like.
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  • #34 17071305
    bodzio012
    Level 33  
    On the first page it says
  • #35 17435472
    waldi822
    Level 2  
    I solved the problem for PLN 46, I ordered a device to support engines on the Allegro that have a problem with starting on a warm one, there are a bit of problems with the installation, as the manual requires, but I did it in a slightly different way, but in accordance with the instructions, and since then I have been reading from a smile on the face of the posts of people who change batteries, starters, new maps install and the problem will remain so. The device that I installed simulates the engine temperature sensor that it is cold, and after starting the device stops cheating the sensor and the car works on real parameters :) and red-hot TDik smokes until it's nice to hear it. I have not noticed any defect, If he would like someone to help you remotely with the installation of the device, I will gladly help ,,, greetings ,,, people who are still struggling with starting a warm vag
    PS -I am not a seller of such devices, I will not send links to buy, (the list of devices can be found on the Allegro after a simple inquiry-Starting a warm disla engine
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  • #36 17435514
    Eidems
    Level 29  
    waldi822 wrote:
    I solved the problem for PLN 46, I ordered a device to support engines on the Allegro that have a problem with starting on a warm one, there are a bit of problems with the installation, as the manual requires, but I did it in a slightly different way, but in accordance with the instructions, and since then I have been reading from a smile on the face of the posts of people who change batteries, starters, new maps install and the problem will remain so. The device that I installed simulates the engine temperature sensor that it is cold, and after starting the device stops cheating the sensor and the car works on real parameters :) and red-hot TDik smokes until it's nice to hear it. I have not noticed any defect, If he would like someone to help you remotely with the installation of the device, I will gladly help ,,, greetings ,,, people who are still struggling with starting a warm vag
    PS -I am not a seller of such devices, I will not send links to buy, (the list of devices can be found on the Allegro after a simple inquiry-Starting a warm disla engine

    And what do you think, the cars leaving the showroom were also hard to start on the warm one? There is a fault and you must find it, not skip it ;) . Often, if the car does not start on hot, the problem is related to the fuel system, and not an "unnecessary" additional sensor.
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  • #37 17435558
    waldi822
    Level 2  
    according to the version of the website quite well-known in my area and with comments on this topic in various forums, the pump and unit injectors no longer have the same values as on the new engine, especially for me where the mileage of the car is 300,000 km and therefore the injection dose parameter is low , any lifting it in the maps results in too rapid combustion. The car is functional, does not smoke, does not stop, no problems with the engine except warm starting, read on the web, ask and you will find out what the problem is
  • #38 17534775
    bigmaster
    Level 15  
    Hello, my Oki II estate 4x4 PD 105Km has the same. mileage 170K miles :)

    so I start the fight on Sunday.
    From the information you read all over the internet :) .

    To check:
    0. engine worn / weak copression on warm. I don't feel like sleeping on the road without the 4.7 l / 100km 4x4 system at 130 km / h. With 4x4 6.5l / 100km
    1. Starter
    2. engine temperature sensor
    3. fuel temperature sensor
    3. Battery
    4. Fuel dose
  • #39 17534985
    Eidems
    Level 29  
    bigmaster wrote:
    Hello, my Oki II estate 4x4 PD 105Km has the same. mileage 170K miles :)

    so I start the fight on Sunday.
    From the information you read all over the internet :) .

    To check:
    0. engine worn / weak copression on warm. I don't feel like sleeping on the road without the 4.7 l / 100km 4x4 system at 130 km / h. With 4x4 6.5l / 100km
    1. Starter
    2. engine temperature sensor
    3. fuel temperature sensor
    3. Battery
    4. Fuel dose


    When you find that everything is ok, have the unit injectors checked. Regards

Topic summary

✨ The discussion revolves around the difficulty of starting an Audi A3 1.9 TDi with a warm engine, with users suggesting potential causes and solutions. Commonly mentioned issues include low fuel injection doses, starter performance, and the condition of unit injectors. Several users recommend increasing the starting fuel dose through VAG-COM adjustments, while others emphasize checking the starter and battery. Some participants mention using devices to simulate cold engine conditions to improve starting performance. The conversation highlights the importance of diagnosing the root cause rather than relying on temporary fixes, with suggestions to consult specialists for proper repairs.

FAQ

TL;DR: About 50 % of warm-start Audi/VW 1.9 TDI cases improve after a 3-minute VCDS dose tweak [Elektroda, jaro860929, post #12582388]; “too low cranking speed, not maps, is the real cause” [Elektroda, majuDJ, post #16825230]

Why it matters: Hard warm starts signal wear or low fuel/rotation, risking pump, bearings and driver nerves.

Quick Facts

• VCDS lead (cost): approx. 40 PLN [Elektroda, jaro860929, post #12580120] • Starter rebuild in PL: ~300–500 PLN [AutoData, 2022] • Cranking speed needed to enable full start dose: ≥250 rpm [Bosch Diesel Handbook, 2005] • ECU adaptation channel for dose: 05, login 12233 [Elektroda, jaro860929, post #12580120] • ‘Warm-start box’ kits on Allegro: 46–80 PLN [Elektroda, damian arl, #12564366; waldi822, #17435472]

Why does a 1.9 TDI crank long when the engine is warm?

Low starter speed reduces the ECU’s injected start dose; worn pumps or injectors worsen it [Elektroda, 12pawel, post #12585235]

How do I check if the starter is guilty?

Measure cranking RPM with VCDS block 001; anything below 250 rpm points to starter or cable issues [Bosch Diesel Handbook, 2005].

What is the safe way to raise the start fuel dose with VCDS?

Use adaptation rather than full remap.
  1. Engine→Login 12233.
  2. Adapt channel 05; increase value stepwise to max +5.
  3. Test→Save, road-test warm [Elektroda, jaro860929, post #12580120]

Will settings vanish if I disconnect the battery?

No; adaptation values store in EEPROM. User reported battery removal did not reset dose [Elektroda, majuDJ, post #16912440]

Is the cheap ‘warm-start box’ a fix or a band-aid?

It fakes coolant temperature to request a cold-start dose. It masks, not cures, the underlying speed/fuel issue [Elektroda, Eidems, post #17435514]

What risks come from maximising the start dose map?

Excess fuel can wash oil from bearings; a tuner warned of “loading the connecting-rod bushings without oil” [Elektroda, majuDJ, post #16825230]

My ABS lamp lit after the repair—related?

The start-dose tweak doesn’t touch ABS. Likely coincidental sensor fault; scan ABS module for stored DTCs [Elektroda, Pablo2828, post #12625713]

Can ECU coding to ‘automatic gearbox’ solve the problem?

It can, but side effects include jerky low-gear drive and an unerasable gearbox error—an edge-case hack, not recommended [Elektroda, b1aster, #16877589; jokerro, #16878172].

When should I rebuild the fuel pump or unit injectors?

If compression, cables and starter test OK yet warm starts still need >3 s and adaptation is maxed, plan pump/injector bench test and overhaul (~1 000 PLN) [Elektroda, andrend, post #12581694]

Edge case: what if the engine starts, then stalls immediately?

Check crank-shaft position sensor; intermittent signal cuts injection despite dose changes [“Crank Sensor Failure Guide”, 2021].
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