Mk1 Cupra R starting struggles

[Hobbsy02]

Hi all, I’ve had my mk1 cupra r for just over a year and love it to pieces, drives mint and pulls like a train! Only persistent issue i have is a starting issue, when starting the car will crank for 3-4 second and coughs to life but does start everytime, if left for 48 hours or so the car will fire up instantly on the button as it should. If i start the car within 20 minutes or so of driving it it will start fine, but left any longer than that it will cough and splutter for 2-4 seconds, unless left for a longer period of time over 48 hours.

Here’s what i have already tried/changed: n75 valve, injector cups and seals, fuel filter, plugs and coils, full timing belt kit, checked injector resistances and coolant temp sensor values via diagnostics all reading fine.

Really stumped with the issue and is the only thing “wrong” with the car, runs absolutely mint, if any of you veterans have any clues or suggestions i’m all ears! Thank you!

 

[mty12345]

Hi mate, my first thought in these cases is always the temp sensor, but I see you have checked the data. Those symptoms are pretty weird! Do you have any fault codes? Do you know what your long term fuel trim [LTFT] number is on OBD2?

I've seen cases on other cars (as in not the 1.8t) where a malfunctioning EVAP valve has caused weird starting issues like this. Could be worth checking out the N80 valve to make sure it's only flowing at the right time. If it's stuck open even slightly then it can allow vapour from the fuel tank to build up in the manifold/cylinders, and that might be making the mixture too rich to combust until the engine has drawn in enough air to clear it.

Another possibility could be a weaping injector that is causing a similar issue. If you have a borescope then you could put it into the manifold and check.

Other than those things, i really can't think of much else that could possibly cause those specific symptoms.

 

[Hobbsy02]

Hi mate, my first thought in these cases is always the temp sensor, but I see you have checked the data. Those symptoms are pretty weird! Do you have any fault codes?

I've seen cases on other cars (as in not the 1.8t) where a malfunctioning EVAP valve has caused weird starting issues like this. Could be worth checking out the N80 valve to make sure it's only flowing at the right time. If it's stuck open then it can allow vapour from the fuel tank to build up in the manifold/cylinders, and that might be making the mixture too rich to combust,until the engine has drawn in enough air to clear it.

Another possibility could be a weaping injector that is causing a similar issue. If you have a borescope then you could put it into the manifold and check.

Other than those things, i really can't think of much else that could possibly cause those specific symptoms.

no fault codes whatsoever mate, a weeping injector has been a thought i will try see if i can rule that out, never considered an evap/n80 valve being faulty but does sound like a possibility, had to recently change my n75 as it was sticking and causing boost issues so maybe the n80 has come to the same fate

 

[mty12345]

no fault codes whatsoever mate, a weeping injector has been a thought i will try see if i can rule that out, never considered an evap/n80 valve being faulty but does sound like a possibility, had to recently change my n75 as it was sticking and causing boost issues so maybe the n80 has come to the same fate

Possible mate, sometimes they get blocked by debris from the charcoal cannister, and don't quite close fully.

 

[Hobbsy02]

Possible mate, sometimes they get blocked by debris from the charcoal cannister, and don't quite close fully.

cheers bud i’ll investigate that tomorrow and report back