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2018 i30N: Hot-Start RPM Drops, Petrol Smell in Oil & HPFP Question

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richardkratochvil6@gmail.

richardkratochvil6@gmail.

New Member
Nov 13, 2025
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Greece
Hello guys, I just bought a used 2018 i30N with 80k km. All services were done every 5–7k km at Hyundai dealerships, so it’s very well maintained.


I have a few small things I want to ask about. Recently, I went to a Hyundai dealership because my local mechanic couldn’t answer. I’ve noticed some hot-start issues after short trips or using N mode, the RPMs drop to 500–600 for about a second, and I need a little throttle to get them back to normal.


I also smell a slight petrol smell in the oil. I heard this can be normal in GDI (direct injection) engines. I did a small test on paper for fuel dilution, and I think there was nothing significant. The oil level hasn’t increased, so I don’t think it’s the HPFP or injectors.


At the dealership, they did a 2-hour diagnosis but didn’t find anything. They suggested starting somewhere and gave me a quote of €1700 to change the HPFP, but they said it may not even be the HPFP. When I asked about the normal petrol smell in GDI engines, the mechanic didn’t know.


Also, I wanted to change the gearbox oil and was looking at Motul Motyl 75W-80. Any tips or advice?


Has anyone experienced similar hot-start RPM drops or petrol smells in their i30N?
 
A lot of people have this issue. There are 3 possible options. HPFP, oxygen sensor or injectors. I have the same issue, so far I changed HPFP - no change, I have new oxygen sensor, just need to put it in, but I don't expect it to fix it and it will be most likely leaking injector which drips into a cylinder and that's why car has issues starting sometimes. HPFP from Korea is approx 130 eur, all 4 injector 400. If your local dealer has equipment, ask them to test all the injectors and find the faulty one, but best would be to replace all at once.

I, and many others, used redline MT oil.
 
IvanV said:
A lot of people have this issue. There are 3 possible options. HPFP, oxygen sensor or injectors. I have the same issue, so far I changed HPFP - no change, I have new oxygen sensor, just need to put it in, but I don't expect it to fix it and it will be most likely leaking injector which drips into a cylinder and that's why car has issues starting sometimes. HPFP from Korea is approx 130 eur, all 4 injector 400. If your local dealer has equipment, ask them to test all the injectors and find the faulty one, but best would be to replace all at once.

I, and many others, used redline MT oil.
Click to expand...
I checked all the injectors, not a single one is leaking... HPFP seems fine as well, because if it was faulthy the oil level would be rising. The issue is only when the car is hot from short trip like 10km. I was thinking also about the MAF sensor to clean, or the throttle opening to clean.
 
richardkratochvil6@gmail. said:
I checked all the injectors, not a single one is leaking... HPFP seems fine as well, because if it was faulthy the oil level would be rising. The issue is only when the car is hot from short trip like 10km. I was thinking also about the MAF sensor to clean, or the throttle opening to clean.
Click to expand...
Try a smoke test, that will show if there's any induction air leaks
 
I saw many many people with this issue, but no solution so far. If you manage to solve it, please share with the rest.
 
richardkratochvil6@gmail. said:
Hello guys, I just bought a used 2018 i30N with 80k km. All services were done every 5–7k km at Hyundai dealerships, so it’s very well maintained.


I have a few small things I want to ask about. Recently, I went to a Hyundai dealership because my local mechanic couldn’t answer. I’ve noticed some hot-start issues after short trips or using N mode, the RPMs drop to 500–600 for about a second, and I need a little throttle to get them back to normal.


I also smell a slight petrol smell in the oil. I heard this can be normal in GDI (direct injection) engines. I did a small test on paper for fuel dilution, and I think there was nothing significant. The oil level hasn’t increased, so I don’t think it’s the HPFP or injectors.


At the dealership, they did a 2-hour diagnosis but didn’t find anything. They suggested starting somewhere and gave me a quote of €1700 to change the HPFP, but they said it may not even be the HPFP. When I asked about the normal petrol smell in GDI engines, the mechanic didn’t know.


Also, I wanted to change the gearbox oil and was looking at Motul Motyl 75W-80. Any tips or advice?


Has anyone experienced similar hot-start RPM drops or petrol smells in their i30N?
Click to expand...
I think there's a recall in place for the high pressure fuel pump for early i30N vehicles
 
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