Questions for some of the more knowing...

[Underground_Killah]

FIrst off, yes. this is not the right forum, but try to get ANYTHING out of the J30 area and you'll realize why i am putting this here.


i'm wanting to put more inside of my car performance wise. It's a 93 J30t by infiniti. i already have bosch platinum +4 sparkplugs, pro rated fuel filter, a new pcv valve, and besides that, it's stock. what can i do that will increase my car's potential and not wreck my checkbook?


also

i've noticed that about 80mph my car begins to rattle and shake.. .but then stops at 90... i haven't a clue on what causes that.

oh, and also my car is idling really wierd (like 400-800 instead of 1100) but it fluctuates... like it'll be at 800, then drop to 200, the go up to 1100.


any ideas? ALL input is appreciated.

[Mr. Luos]

Is the car pretty much stock??

Plugs probably run too hot for it. Try a more basic plug. Maybe something from the factory.

[Underground_Killah]

nah it was doing thta before i switched plugs (the idling all of it...) and they are recommended for it as well (it's platinum tipped...)

[chevytrucks92]

You probably have some kind of Throttle Positioning Sensor that is causing your RPMs to fluctuate like that.

I would assume its in the TB somewhere, but I really have no idea for that type of vehicle.

[Underground_Killah]

ok, well what about performance? what can i do?

[Mister_Sinister]

Yeah, it sounds like you need to adjust your TPS sensor. Lemme go check on where it is on the Tib. I'm pretty sure there should be some sort of screw on the TB that you can tighten down to fix that.

As for performance, upgrade the big 3: Intake/Exhaust/Headers. Lightweight pulleys would help too. You could also have the Intake Manifold bored up. If you do that, be sure to get a bigger throttle body.

If you have more to spend, you could get a fuel-tuning system, better fuel injectors, high duration cams, high comp pistons, etc.

[TypeS]

It could also be your oxygen or MAP sensor.

As far as racing performance, new spark plugs, cables won't do pretty much anything that will make you go faster, unless the old ones were really bad. I consider new sparkplugs and a new fuel filter maintnance, not performance mods...at least not most cars on this forum.

You should check an infinity forum to see what the best mods would be. All cars respond to different mods differently.

[fierangero]

a big ricer wing and lots of stickers will make it SOOO fast!

[i3o2Matt]

hmm...the +4's are a waste of money i've heard...but i would at least modify the intake, headers, find a y-pipe, high-flow cat, exhaust.

[CassiesMan]

As it was said by Mister Sinister (it woulda been me, if my internet hadn't crapped out seconds beofre I hit 'submit post', lol), the best bang for your buck is gonna come from Intake, Exhasut, Headers, and possibly a bigger throttle body. The engine is basically a giant air pump, and the best way to get it to work better is to let it breath more freely. Once you get those, see if you can find a chip or software to take advantage of those mods. Then, put your car on a diet.

[bad360rt]

Just a shot in the dark here, since I know absolutely nothing about your car, but does the t stand for turbo? If so, can the stock block handle more boost?

[TatII]

the shaking sounds more like you need your wheels balanced, since its only at a certain speed that does it, this means that the wheel is tramping and shimmying at a certain frequency thats causing it to shake. i think if its a tps sensor then it always bog down whenever it hits that throttle angle.

also if its the 02 sensor, he would notice a big drop in fuel economy. it sounds like either a unbalanced front wheel or wheels, lift up the front of the car, to check if your front end is loose ( check tie rods ends,ball joints, and wheel bearing ) you can check by lifting the up, and by tryin to wiggle the wheel. if it wiggles, theres your problem.

[BP2K2Max]

the T stands for touring.
iirc, that's detuned 300zx motor in that car. there are plenty of mods available for that thing.

for the poor idle, i'd say it's either the idle air control valve(iacv) or your PCV valve. Also check your Mass Airflow Sensor.

[kfoote]

Originally Posted by CassiesMan

As it was said by Mister Sinister (it woulda been me, if my internet hadn't crapped out seconds beofre I hit 'submit post', lol), the best bang for your buck is gonna come from Intake, Exhasut, Headers, and possibly a bigger throttle body. The engine is basically a giant air pump, and the best way to get it to work better is to let it breath more freely. Once you get those, see if you can find a chip or software to take advantage of those mods. Then, put your car on a diet.

Without knowing too much about the J30 and what exactly is available for it, this is a very good guideline to go with, except I'd throw in an underdrive pulley kit (again, if available) as a good bang for the buck mod.

Also when to do the software depends a lot on what is available. With the exception of the bigger throttle body, most plug-and-play software won't have different programming for intake, exhaust, pullies, or headers. If you're going the custom tuning route, then you'll definitely want to do the software last.

[TypeS]

Originally Posted by TatII

also if its the 02 sensor, he would notice a big drop in fuel economy.

Not neccessarely. When I got the header in my old civic, the O2 sensor started acting up and I had an erratic idle, but I got better MPG. I was averaging over 40 mpg on the highway whereas it was less before that. Once I replaced it, it went back to below 40 mpg. The reason I know this is because I used to take the same long trips week after week and I'd have more gas left after the 02 sensor started acting up. A lot of people think the car always runs rich after the 02 sensor goes, but that's not always true. But you're right that the MPG should change since the ECU doesn't know how much fuel it needs. But it can also be a benefit MPG wise, but obviously you'll lose performance since not enough fuel is injected to go fast.