Struggling to start
Q I am experiencing a little problem with my 2010 Skoda Octavia 1.8 TSI (engine code CDAA) that so far I have not been able to resolve. The car normally starts and drives fine but on the odd occasion it struggles to start. This only seems to happen when the engine is already at running temperature. The engine actually cranks over and starts, idles for a moment then coughs splutters and cuts out. Trying to start the engine again, it does exactly the same. Giving it loads of throttle whilst its spluttering does get it running after revving it a bit for a minute or so.
I’ve had a good look around the engine bay and checked wiring, connections, pipework, etc. But all appeared OK. I’ve connected my laptop with VCDS software to it, no faults were shown. Readings from the various sensors all looked OK. I’ve tried to replicate the fault with the laptop connected but it started up fine every time.
On one occasion when this happened in a supermarket car park, a mechanic that was parked near us plugged his code reader (professional machine) in, but it didn’t shed any light on what was wrong.
Around four months before this started to happen I had given the car a full service, oil (Castrol Edge 5W-30 LL), oil and air filters, spark plugs. After the first time it wouldn’t start, I changed the fuel filter – it hadn’t been changed for many years. But this has not resolved the problem. Any ideas what the problem could be?
Liam Hoskin A As the problem only occurs when the engine is hot and as by holding the throttle open, does seem to clear and assist in the starting and running, this suggests that it is possibly an over choke situation that is at the root of the problem. This may be caused by a defective engine coolant sensor which is reading incorrectly or by an injector fault which is allowing an oversupply of fuel.
Neither problems would necessarily trigger a code, and so would be worth investigating. The temperature sender unit should give a reading which can be read-off using live data, and it may be found that with a hot engine, which should be reading around 90°C, this is delivering an incorrect reading to the engine control unit, triggering a rich mixture to be delivered.
Testing can also be done using an ohm meter, and with the sensor disconnected the reading with the coolant temperature
at 21°C should be around 2460 Ω and with the engine hot and the coolant at around 102°C the reading should be 190 Ω. The wires to the sensor are Yellow and Brown.
If no problem can be found with the coolant temperature sensor, then it may be worth checking the air intake temperature sensor. The readings for this with an air temperature of 21°C should be around 2150 Ω and with an air temperature of 43°C will be around 703 Ω.
According to the details I have for your engine, it has two air intake temperature sensors – one incorporated with the MAF sensor and the other in the inlet manifold. Again, testing these with live data may be an easier option.
If after testing the temperature sensors no problem has been found, then the next step would be to get the injectors tested to ensure these are not allowing excess fuel to enter the induction system.