Salutations everyone,
My once-smooth N53, which has 100,000 miles on it, has recently begun to exhibit some juddering during cold starts. I intended to examine my injectors and spark plugs to determine the source of the problem. After deciding to remove the engine cover, I discovered a huge oil leak caused by a failed oil gasket. So, I decided to get a new gasket and valve cover from Febi and swapped it out. As part of this process, I removed each of my eleven index injectors to check for damage and leaks. The INPA diagnostics showed that the fuel mixture correction values were changing in real time, so I suspected that the injectors on bank 2 might be leaking. Having said that, there was no apparent fuel smell or other issues with the injectors. I made sure there wouldn't be any fuel flooding in the cylinder by connecting them to the fuel rail and cranking the engine to test for leaks.
The engine is having trouble starting, has a very uneven idle, wildly fluctuates in RPM from 500 to 1500, and seems like it could stall at any second after I reassembled everything. After removing the oil filler cap and restarting the engine, a strong odour of burnt oil and white smoke could be detected.
From what I can tell, this is a textbook example of air going into the engine without a filter. I didn't replace the injector's Teflon seals, but they're the only possible culprits. There was no need for a specialised tool when I extracted a couple of injectors for inspection purposes; they came out relatively loose. I have noticed two new codes in INPA after replacing the valve covers: 0x29E0 and 0x29E1. These codes indicate that the mixture control on banks 1 and 2 is not up to par.
Based on my visual inspection, the sealing appears to be in good condition, and I followed the torque sequence for the valve cover. With the new valve cover in place, the PCV hose is securely attached, and the membrane should also be OK. Since the coil packs and spark plugs were previously functioning properly, there should be no issue with them now.
I didn't see anything mentioned about replacing the injector seals, so I was wondering if anyone had experienced something similar. My next move will be to remove each injector and replace the Teflon seals with new ones.
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Joined: Mon Apr 06, 2026
Posts: 26
Joined: Mon Apr 06, 2026
Teflon seals are not reusable because they are designed to crush or deform only once.
Posts: 61
Joined: Mon Apr 06, 2026
When the injectors on a smaller N43 engine started leaking, I had to replace them. A strong pull was all it took to remove the injectors; no special tools were required.
The spark plug is a simple indicator of injector leakage because it is often wet and black in colour, unlike good spark plugs. Taking the injector out for testing only adds more hassle.
Never again will I buy a used injector off of eBay without the specialised tool needed to replace the Teflon seal. It would be more prudent for you to replace all six seals at once rather than wait for someone who has experience re-fitting injectors with old seals to come along.
The spark plug is a simple indicator of injector leakage because it is often wet and black in colour, unlike good spark plugs. Taking the injector out for testing only adds more hassle.
Never again will I buy a used injector off of eBay without the specialised tool needed to replace the Teflon seal. It would be more prudent for you to replace all six seals at once rather than wait for someone who has experience re-fitting injectors with old seals to come along.