I cannot figure this out
 

I purchased my car approximately 7 months ago with 48k miles. From the get go ive always felt like the car was quick, yet it felt so much slower than the specs of the car. i figured that it was just in my head and that there was nothing wrong. Except last night, i started up my car and all of a sudden it felt like i was driving a brand new car... The gas pedal was much more reactive, i was going through gears much quicker, and was practically snapping my neck through second gear:driving:. Normally this would be a great thing, except that it highlights that there is a problem in my car somewhere. I'm usually somewhat knowledgeable with my cars but this time, I literally don't know where to start. Does anyone have any insight or suggestions on the matter?

to add; it sounds messed up, but for the first time im actually in love with my car... I want to keep it this way obviously. So any help would be greatly appreciated.

Thank in advance

Throttle lag is a common issue. Do some research on it. I don't notice it but I probably always have had it in the hot climate I am in.

Thats what i assumed since i purchased my car, but literally after 7 months my car had a huge gain of power at complete random yesterday.

Mine actually feels like a dog now since it has turned hot, especially in the low gears.

Weird, mine did the exact opposite. I don't understand what's up with it


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Its possible there were some very wonky fuel trims that took a while to sort themselves out. It's also possible some crud was caked on the MAF's that finally flew off.

Finally, different fuel mixtures, which vary a bit by season, can affect things a bit.

Either way, sounds like a good problem to have :)

Butt dyno is highly inconsistent.

^^ There is really no where for this to go until you get it on a dyno.

I agree that butt dyno is highly inconsistent but you have to understand that ive been driving my car for 7 months. I know how it feels and if you felt this difference you would see how dramatic it is. Im not talking slight differences, i mean it literally feels like my car jumped around 50-75hp. Passengers have even noticed the difference.

I agree, but im afraid a dyno will only show the power now, not the power before this occured.

:icon18:LMFAO....that just made my day, so rare, but true.

Anyone got any more input on this?


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I should also input that I ran my car to almost empty before filling up (which I rarely ever do) the next day my car had this gain of power. As I said my car used to feel like 220-250hp now it feels like what it should.


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No useful information here to even speculate. Next time its slow, take it in for service.

well, could be so many different things. I like to start with cleaning the MAFs. when they get dirty they can make your car run finicky.

As has been mentioned, there are soooo many variables that could affect power output. Without a baseline log to compare current values to, everything is just a guess.

There's always the possibility that a sensor has messed up and the engine is running leaner or richer than before. Might be a good idea to check AFRs, &c.

Yeah that is what is making this so frustrating for me. I went ahead and cleaned the MAF sensors (Although they were pristine). I'm not sure if getting a mechanical inspection would be worth it or to go ahead and try to do some dyno tests. Either way im afraid it will be more money and trouble than whats its worth.

I'd suggest an http://www.the370z.com/nissan-370z-o...ml#post2446302 if it ever felt slow again

I actually did do this a few times.

Update: So I took it to Nissan and had them do a full inspection. Since the car was not having the intermittent issue at the time they could not find a locate a direct cause. The head mechanic did however mention that he had one car have this issue before and eventually they located the issue: bad fuel injectors. They also mentioned that there was a misfire code, although i did not have a misfire issue, which would hint that the fuels injectors are indeed the source of the issue.

Anyone have any suggestions on replacing those?

Well i have had this issue for some time my self and i finally figured it out,

what has happened to me is that my O2 sensor on Bank2 gives High voltage on cold start 2.59v is hella high, compared that its suposto give 0.1-0.9v or so during its normal operation, witch triggers more fuel adjustments to bank 2, now its not hitting 14.7:1 but more like 11s:1 ratio on one bank.

now this does not stay like that for too long about 6 min until the sensor reaches to some temp point and goes to its normal operating voltage, this made it hard to catch since i warm the car up every cold start.

only one time the code P0158 popped recently when i was running late for work and didnt warm my car up, which caused me to record my perimeters to see wft is going on on cold starts.

GL OP i hope this helps.

Is it under warranty? Just have new ones installed.

If not, you'll need to send them out for testing if you can't figure out which one is running lean via spark plug inspection. Make sure it isn't just a bad (fouled or corroded) plug or damaged coilpack too.

Or you could try an injector cleaning service. As in pressurized special solvent cleaning, directly pumped into fuel rail, not just a fuel additive.