Thread: Name that misfiring symptom cause - Now with Video of car running.

So.. The NX is able to be deemed mobile again. However, after sitting in storage for several years ( but started and run regularly), it seems the car has developed a recurring misfiring problem.

This started about a year ago and i had thought I fixed the issue by changing the plugs. The plugs that were taken out did not look fowled or in bad condition.
I run NGK Platinums.

The Distributor cap and rotor look A-OK and the coil plug as well as spark plugs have no cracks or wear signs.

The gas that has been sitting in the car has not been over 9-10 months old, and has been treated as well.

Keep in mind, here is the twilight zone aspect of the cars symptoms..

The car only misfires after It has been driven under full throttle above 4K.

I will let the car warm up, cruise for a bit etc. When i let some pressure get through the engine and let it rev only then will the symptoms occur. But only after i have gone through whatever gears in the higher RPM range. so say.. I let it get above 6K in 2nd and 3rd, then shut down to a cruise and put it in 5th.. then Bingo.. I sound like a subaru. the car will then not stop. I can then let the car sit for a couple days and it will start back up fine.

Something tells me this is more fuel system related, but I don't have much experience diagnosing these issues. I dont want to rush and do anything drastic without any pointers or ways to narrow down what could be the issue. Please help, this is the only thing keeping me from attending a local AutoX for some needed fun time with the car. Thanks to any who help!

I'd say, injectors.

My GA would do the same thing, but opposite.lol
Under 4K in any gear it sounded like a subbie and idled like a cammed V8. And only when hot, on cold days it ran perfect.

X2 on injectors. Sounds like one may have gone bad on you. Get it to misfiring and listen to your injectors one at a time and hear if one sounds to be firing awkwardly.

Here is a video showing the car misfiring.

Unlike before where the issue went away on its own after starting it the next weekend, it looks like this is worse now and its here to stay for the time being. I could not hear any noises from the injector area.. so im kind of lost. But I am definitely in "Subaru" Mode.

NX misfire - YouTube

I didn't look at the video, but let it idle and pull 1 plug wire off at a time. If the idle doesn't change when pulling 1 wire, then you have an issue with that cylinder. If the power isn't there, and it is idling rough - probably an injector.

Are you high port or low port? High port is very easy to change an injector; low port takes ~1.5 hours.

Josh

Im going to guess injector or injector wires near the injector clip.

Since its sat for a while its a good possibility that it could be a leaky injector causing the issue. If it just sounds like a suby all the time now, definitely going to say injector or broken wire to the injector clip. Usually right at or just before the clip.

Once you isolate which cylinder is misfiring by pulling up wires one by one you can start looking for the source of the problem. Once you find the cylinder misfiring give the injector clip wires a little tug as far away from that clip as you can and see if one of them breaks completely. Ive seen this happen multiple times. If so then you will need to replace the clip. If not then I would bet injector.

thanks ashton. So you are saying to pull the plug wire one by one to check and see which cylinder isn't firing then?

I didn't get to it today, but i was going to pry out the spare set of 259cc injectors from the bent fuel rail that came with the JDM engine that is in the car now. The original injectors and rail were used, so they have 150K on them. I would not be surprised to see that it is the injectors.

If in case it is the injectors.. what is the next steps I should take?

Should i throw in this other set that has been sitting around with no known mileage or condition ( my gut tells me hell no)..

I have been looking on the side to send these spare injectors I have to be cleaned professionally, does anyone have any recommendations?

also, when I change the injectors, what misc. bits will I need to do this once and right? When it comes to the fuel system i have always overlooked the process/parts as I normally just see shiny suspension bits and get add. I know there are O rings that people complain about, but besides that I am not in the know how.

I would see no issue using the injectors in the bent rail that came with the jdm motor. Ive had injectors from jdm motors that sat in my garage for years and I used some of them when I was home on vacation in my buddies car and they worked perfectly. His nx had a dead injector.

If its not the wiring to the injector and you go through with replacing it, just make sure to lube up the o-rings well before putting the new one in. I usually just use spit and it works well.

Yes, with the motor running and misfiring pull the plug wires up one by one and see which one doesnt change the way the motor runs. That isolates your cylinder that is misfiring once.

It must have known that there is an autocross 20 mins away from me today, as it started right up today. I made it into the closest town to fill her up with some 93. I think i will just baby her up there, say hey to the guys and watch and have some fun. I think she just needs to be driven.