Fuck guys.
Do you all seriously just throw parts at your cars and hope that it will start running better sooner or later?
Do you know that is actually the wrong way of doing it right?
It is shit like that, that makes everyone think that 240 drivers are totally retarded.
Can any of you even take the time to explain why you thought any of your suggestions might have been the issue?
Or even better yet, can any of you actually read the post and comprehend what was said in order to distinguish what the actual symptoms are?
Here, I'll help you out. I'll delete all of the extra crap and keep the important stuff.

Ok, so a possible miss fire at highway speeds under rather light load. Depends on what exactly the OP considers a split second, it could either be a simple misfire, or it could be a very brief moment where the engine bogged down and then caught right back up.
So this tells us that it most likely only happened once on that ride home. It would be safe to say that there were at least 5 more miles driven after that split second loss of power.

Ok, so since it happened at a stop this time, it is unlikely that it has anything to do with speed. It can also be safe to say that at this point, it has little, if anything to do with load. Not much load involved at a stop.

we know that 800 rpms isn't really all that low for an idle. But it would be worth asking why the OP thinks that is low. Did it used to be higher? Is it supposed to be higher because it is an automatic? Has he even had the car long enough to know what it used to idle at?

Guess that answers that question.

the OP is worried it might be a transmission issue. HHmmm... I wonder what the OP knows that would make him suspect a transmission issue.. Need to ask him to find out. Believe it or not, people don't always post every detail about the situation in their first post.
Since he thinks it is going to cost a buttload of money to have the transmission issue fixed, then we can figure that it is either A) an automatic transmission B) he is very new to 240s in general C) he has all of his work done at a shop. One, or a combination of each. Automatic transmissions to fix them the correct way, can be costly since most people don't have the skills to be able to fix them themselves. I personally have rebuilt engines, but wouldn't screw with an automatic tranny. Just not my deal. So it isn't anything for sure, but we can use it to help guide our thinking.

again, he hasn't owned this car very long.

Two things here. First, we can figure that this guy is more than likely one of those people that makes an effort to maintain his vehicle since he gave it new plugs and wires from the get go. Second, Why exactly did he feel like he needed to replace the plugs and wires? Was there a reason for it? What else was done?

A long time huh? According to what? Why does the OP think it takes a long time? Are we talking about it staying in second gear for a longer than normal amount of time? OR is it taking a long to to actually shift from second and into third?
Since he said the car takes a long time, this would affirm the thoughts we already have about it being an automatic, but because we don't want to take anything for granted, we're going to ask anyway. We already know that people have posted stranger things before.
What is the OP comparing this to? A totally different car? a previously owned 240? A buddies 240? Or just a feelin?
Has it always shifted like that? Or is this a new symptom that started about the same time as the "split second loss of power"
Shouldn't make much difference, but at least we know we are working with an S14.
The exhaust means we would be able to more easily hear misfires.
The intake tells us that it is more than likely not properly secured and is just loose and hanging there like 99% of all aftermarket intakes, especially the AEM ones since they don't even come with brackets to secure it new. Since it is loose, it could mean that it is vibrating around and the MAF plug has gotten worn and loose. Its a rather common issue and if it got bumped in just the right way, it could cause a split second loss of power. Vibrations and bumps happen at both 50 mph and idle. So thats a possibility.
So the issue just started and so far it appears to have happened only twice in two days. Beyond that, it appears that it is running, driving, starting, etc, just fine.
So the only issue is a sudden, "split second loss of power"
So the OP is looking for some suggestions and feedback so he can check things out as soon as possible. So we can rather safely assume that he'll be back to be able to answer any questions we might have to be able to get some more information out of him to offer even more accurate advice because we want to help him out, not tell him bullshit information using the excuse that you have to spend a ton of money and throw parts at your car to be able to figure out what is wrong with it. We're smarter than that. Smart enough to know that if we can't come up with an educated, intelligent, suggestion, that we'll be able to recognize, not only our lack of knowledge, but also our sheer lack of understanding, and therefore, keep our mouths shut.


See how much information you can get out of a single post?
And hell, this wasn't even a totally perfect post. Decent, but not perfect.
Now, lets review our notes so we can begin to form a response.
-So we want to know what the OP considers to be a "split second" since this could dramatically effect the possible causes. Perhaps we could ask: What exactly do you mean by split second? Are we talking about a single misfire, or was it different than that? We talking like literally less than a second, or was it maybe a couple of seconds?
-From there, we assumed that it happened only once on the ride home, but we want to be sure, : Did it only happen once on the ride home? How long did it run after that split second loss of power?
-We wanted to know why the OP thought a 800 rpm idle was a bit low: Why do you think that 800 rpms is a bit low? 240s are actually supposed to idle right around there.
-Why does the OP think it might be a transmission issue : What makes you think it is transmission related? Is it doing anything else that makes you think it could be the transmission?
-When the OP bought the car, why did he put in new plugs and wires? : What made you install new plugs and wires when you got the car? What else was done to the car?
- Why does the OP think it takes a long time to get passed second gear, and what exactly does that mean? : It is an automatic right? Why do you think it takes a long time to get passed second gear? Do you mean that it is in second gear for a long time, or do you mean the actual shift from second to third takes a long time? What are you comparing this time to?
- That intake could be bouncing around and hitting the MAF sensor plug, lets ask our questions first, then post that as what we think it could be so far : Is your AEM intake secured, or is it just attached at the throttle body? If it is loose, chances are it is bouncing around and that is putting stress on the MAF sensor plug, wearing it out and making it loose. Those split second losses of power could have been the plug getting bounced just right and causing it to temporarily come loose. That brief disconnect could have caused the engine to die for a split second and as soon as the plug settled and connected again, it would have gone back to normal. A lot of people will take a zip tie and zip tie the wire snuggly to the intake pipe to try and keep the plug tightly connected. It would be better to also secure the intake tube to stop it from flopping all over the place.
- the OP said it was a new issue, and only discussed it happening twice, was that it? : Did it only happen those two times? So once a day?
- the OP is concerned about making it home, : Why do you think it won't make it home? Is it getting worse?

Now, take all of that and compile it into a single, decent, halfway intelligent response.

What do you mean by "Split second" ? Are we talking about a single misfire, or was it more like the engine bogged down for a moment, and then immediately caught up and was back to normal? We talking literally less than a second, or was it maybe a couple of seconds?
Loss of power as in the engine started to die, or do you mean electrical issues?
Did it only happen those two times?
Is it getting worse?

Since it did it both while moving and while sitting still, it is unlikely that it is the transmission, unless there are some other symptoms.
240's are technically supposed to idle right at 750 rpms, but pretty much anything under 1,000 is pretty normal. So your 800 rpms is pretty typical. It won't hurt anything to leave it that way, but if you wanted, you could actually adjust the spark timing a little bit to try and bring it down just that touch more. not really a big deal. The key is that it is even and consistent.

Did you install new plugs and wires because of this issue, or was that before anything was wrong? Have you don't any other work to the car? before this issue? Trying to fix it?

It is an automatic right? When you say that it takes a long time to get passed second gear, do you mean that it is in second gear for a long time, or do you mean the actual shift from second to third takes a long time? It doesn't seem like the two things are related, but if the tranny is giving you shifting problems, then it is possible that the fluid has more than likely never been changed. A full change would probably be a good idea, but even just changing the filter and topping it off would be a big help. That lucas transmission stuff seems to do a pretty decent job at helping out an old tranny. here's some interesting info on the 240sx automatic tranny - Ultimate Guide to Nissan Automatic Transmissions

As far as that split second loss of power, I would be willing to bet that your intake isn't secured beyond just where it connects to the throttle body. Chances are it is bouncing around while you drive and that is putting a ton of stress on the MAF sensor plug. All of that movement can wear out the plug causing it to loosen up. Then, all it takes is just the right bump, and the pins inside the plug loose contact for a moment. That brief disconnect causes the ECU to think the MAF just took a crap and it wants to drop the RPMs and dump fuel. When you were driving down the road at 50, you could have hit a bump in the road just right to cause this and when you were at idle, the engine could have been shaking in just the right way to knock the plug around. A lot of people will fix this by taking a zip tie all the way around the intake and the wiring, so the wiring is snugged up against the intake. This puts pressure on the plug to keep it in place. A step better would be to secure the entire intake pipe, and air filter to keep it from bouncing all over the place. I had mine so that the plug was held in place, and so the intake tube was held down. That way the wiring wouldn't shake around, and the plug couldn't get hit on anything.
If there aren't any other symptoms, then I would start with checking out that plug.


See how that covered all of the bases, asked all of the right questions, and suggested a possible issue that made sense?
Now, the OP can go inspect the correct thing, isn't wasting time and more importantly wasting money throwing random parts at the car. And if the OP comes back with answers to those questions, we can then narrow down what else it could be because we'll have some more information to work with.