CantZme

So I recently purchased a 1990 300zx TT. Orignal TT verified by vin.
Black leather, 2 seat. 5 spd. T-tops. Pearl white. Beautiful car. There was a hesitation when i bought it. But it had been sitting for a year and a half before i bought it so i thought it would work itself out. I got it home and changed the spark plugs (NGK laser platinum's i believe) Put in full syn. 15w-50 Mobil 1.

Then the car started to hesitate and studder even more along with idling rough, but clear itself out almost around 2600. I went through and unhooked the coil packs and all seemed good up until the top right cyl. The idle didnt change.
I ran a compression test. registered around 150 on the cyl that was seeming to have the issue. I switched that coil pack to a cylinder that i knew was good. And the coil pack wasnt the issue.
So I came to the conclusion it was injectors. I took off the intake manifold. saw that someone had been in there before but only changed 3 inj. none of which were the problem cylinder. So in hopes to save money and they did look almost brand new. I only bought 3 more and replaced the old injectors.

Put it all back together and started it. Seemed to be running better than before. Took it down the road, nothing at first. but then the hesitation came back. What could possibly be the issue....

NismoPick

Welcome to ZDriver!

Did you try pulling the ecu diagnostic codes?

CantZme

The check engine light isn't on but it does work. So I'm not sure where to start.

Rupe

How to check the codes of the ECU in a '90-'95 Nissan 300ZX

That's what Nismo was referring to.

CantZme

Thank you for showing me that, I will be back with your answer on that as soon as I get a chance

Skully

If you unplug the MAF does it run better?

Long read if you want...

I recently started having issues similar to yours...stumbling, hesitation, would even stall....It was annoying, bad part was it would do it over a bumpy road even worse!!! Came home opened the hood wiggled everything, seemed ok. Slammed the hood, car stalled. Started it up, opened the hood and hit the front of the rad support, car stalled. Did some research, and it came to conclusion it was MAF, as you can do a "bump" test on it to see if its good or not, you gently tap the MAF body when car is running and if it affect the way it runs or kills it, its the issue. Did more searching around apparently the solders INSIDE the housing, go bad and crack from plugging and unplugging the maf or just over time.
This video shows what I am talking about, and this was my exact issue..one of the leads must have cracked the solder last time I unplugged the MAF


Hope it helps sorry for long reply. I resoldered all 4 points, cleaned the MAF, went for a drive, smoother idle, no stumbling, no hesitation, drives awesome.

Rupe

Interesting! I might check that out for the hell of it.

CantZme

It gave me a 55, so I'm so far beyond confused. My cats are stopped up, so im going to hull them or cut them off completely and weld new pipe along with replacing the fuel filter today and go from there.

CantZme

And I'll check the maf as well I appreciate the input though guys

Skully

Yeah it wasn't throwing codes for me on the MAF at all just ran like **** from time to time. Cats can contribute as well!

CantZme

It's hard buying a new car and trying to sort out the old problems but I guess that's what you have to deal with haha

Skully

Fun and headaches at the same time...it does suck if it is your only driver tho.

CantZme

Wasn't meant to be but turned into it, I'm stuck driving my girlfriends pink eclipse haha

CantZme

A more detailed experience of what happens this, I Just put on a new fuel filter, cut cats off, and its still doing it. It seems to run on all 6 when I first take it out but once I hit high rpms it starts to hesitate and almost like jump. It will clear up if you're getting on it for a moment but then it starts doing it again, it never fully clears out once it starts, I don't understand it

CantZme

And I'm gonna check out the maf and ptu today

spank61

if the check engine light works, but doesn't come on, even with the cats gone, could be someone replaced the eprom chip in the ecu, it's some pretty tricky soldering, if the injectors aren't matched to the eprom chip, it will run, but like ****, its easy to check, go to robo's z website there is detailed instructions there