Misfiring issue - need help with next step

[Jamesdeane]

Hey Everyone,

I've been troubleshooting a misfiring issue on my 90 r32 gtr. I've isolated the issue to the fuel injector on the 5th cylinder. Fuel was leaking from the hose that feeds the fuel rail for the back 3 cylinders. I've never removed a fuel rail or injector before so I thought I would ask for advice first. Is it possible the injector just needs to be cleaned or would it be better to just replace it? If it just needs to be cleaned I figured it would be a good idea to clean all 6. I'm running on the stock 440's.I figured it might be a good idea to replace the fuel filter as well.

Thanks in advance.

[nimblestix]

Just for my own reasons, can i ask how you narrowed it down to an individual injector? Might help to come up with a solution if we know what the route cause is and how you came to that.

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[Jamesdeane]

Pulled the plugs to the coil packs one by one while it was running. When I pulled the plug from cylinder 5 there was no change in how it was running. I checked for a spark on cylinder 5 and there was. At that point I noticed the fuel leaking from the hose. I tried pulling the electrical plug on cylinder 5 fuel injector while it was running and noticed no difference.

[Dakota_gsx]

If the injector is leaking itself, then try to find out if it is the o rings that are leaking or if the injector is actually cracked some how. Try to check electrical too going to the injector. Not sure exactly how to test it but maybe try unplugging the electrical from that injector and check if you are getting a signal. Just cause you are leaking fuel doesnt always mean you should be mis firing every single time. It may but i think you should check just in case.
BTW the o rings are all the exact same out of a 90 240sx Ka.

[Jamesdeane]

So I brought the injectors in to be tested and they are 100% pefect across the board.

The engine was rebuild by autodream last summer and they said they had to replace a chip on the ecu as there was issues with it not firing in cylinder 5 when the engine was reinstalled, I'm wondering if this issue came back. I plugged the leads of my multimeter into the connector on that injector and I was getting voltage out of it, what should I be seeing?

[BrianV8]

What it might be is the wire hanging on the ecu has a small brake right at the ecu connector. I had i think all mine eventually cause me a problem 1 by 1 from moving the harness around so much installing and removing the ecu

[Billy_Jack]

Have you replaced the plugs at all, sufficient spark to atmosphere doesnt always mean sufficient spark in the cylinder, and they are cheap

[Jamesdeane]

I swapped the coilpack and sparkplug with another cylinder and the issue persisted in cylinder 5

[BrianV8]

I swapped the coilpack and sparkplug with another cylinder and the issue persisted in cylinder 5

Wiggle the wire that fires injector #5 at the ecu see if it comes back

[cschepp]

Another thing to check for is something simple, check for the spark plug yapping and make sure you have the proper heat range for your motor. I did some research when I had to replace them on my 26 and they are ngk bkr7e spark plugs. Heat range is important just as much as gapping them properly. .8mm gap is what you should look for.

**** number one rule when diagnosing start with the easiest, most likely thing and work your way across the board. This is always the best way to save yourself some cash and hardship*****