Bad fuel injector?

[MURDERGOON]

So I was removing some emissions junk and coolant lines going to the intake on my ka24e and I decided to give my injectors a thorough cleaning using a trick I used to do on my z-car. What I did was pull all the injectors and use a syringe body that will fit tightly over the inlet of the injectors with the plunger removed. Then I use a can of carb cleaner to pressurize the syringe body with the little red straw it comes with. After its pressurized I pulse the injector using a tattoo power supply and a pigtail set at 5-7 volts. This trick works awesome usually but this time I ran into a problem. Three of my injectors are shiny and silver bodied with a red plastic connector. Those three fired at 7 volts without a problem and sprayed really nicely. The last injector has the same red top but the metal body is black and it won't pulse under pressure unless I crank up the voltage to 10! I can get it to open at lower voltage if I fire it dry or if I pressurize it and push the pintle in while I hold the foot pedal down to supply voltage but as soon as I let power off and try again it won't pulse...
I checked all of them with an ohm meter and the three newer looking ones sit at 14 ohms. The black one varies between 13.9 to 14.1. Is the solenoid possibly weak in that one injector? Or does the ecu supply more than 10v to pulse the injectors. The car is a little harder to start than I think it should be, and is getting poor fuel economy. No codes showing. Replaced o2 sensor, coolant temperature sensor, timing chain guides, and rod bearings. Any help would be greatly appreciated!

[frapjap]

Welcome to NICO! Have you got any photos of that car?

I think you've identified your problem, honestly. The next step would be to grab another injector from a junk yard or from the classifieds and see if your hard starting and fuel mileage improves.

[MURDERGOON]

Ya i think thats what im gonna try. I did double check my tattoo power supply and the voltage reading was off. By a few volts. The dark one will open under pressure at 5.5 volts sbc the other three will open at 3.5 volts. From what I've read, the ka24e puts full battery voltage to the injectors. At 12 volts they all open fine. Does this still mean the dark one is bad?

[PapaSmurf2k3]

I THINK fuel injectors are on/of or PWM type solenoids as opposed to VFS, so the ECU should just fire 12 volts to them for different amounts of time. That SHOULD help with a laggy injector like you have, but the response time may be a little different on that one injector compared to the others (we're talking milliseconds or sub-milliseconds here).
Your options would be to send them out and get flow tested to see if they are well-matched, or to just do what Ray said and pickup another injector and try it out.
I'd probably start with the latter.

[MURDERGOON]

Well i got it all back together and running after shaving the extra vacuum lines off the intake and tucking the wiring harness under the manifold to clean things up but now for some reason I can't get the timing setting to stick and the idle is still acting funny. I cant get the idle to go under 1k even with the screw on the back of the intake all the way in and the one on the throttle body backed off... I also tried to reset the timing on it. With it warmed up and the tps disconnected it sits at the second to the last mark like I've read it should. I shut it off, reconnect the tps and it's sitting at the very first mark... I've tried everything I can think of but it just won't stay at 15 degrees like it should.. The only code I'm getting is code 41 (intake air temperature sensor) which is new as well.. This is making me want my v8 back...

[PapaSmurf2k3]

Almost sounds like you have a vacuum leak.

[MURDERGOON]

Just smoke tested it. Not a single leak anywhere... Looks like I'm checking grounds now...

[MURDERGOON]

On the idle thing, I checked the iacv and it's moving freely,but here's the weird thing. If I pinch the hose up by the intake that feeds the iacv and the air regulator the car will die. I completely pulled the iacv solenoid and plugged it off and it still does the same thing. Maybe the air regulator stuck open? Is it necessary to be on there? Or can I just block it off like I did the egr?

[MURDERGOON]

Ok so I just found this article about some crimped connections in the harness right behind the #4 fuel injector. I guess Nissan put out a service bulletin on it. I just went through and fixed both crimped connections and my code 41 is gone now. The engine idles at 750 just like it should too. My timing problem is still there though... I can warm it up, unplug the big connection on the tps, start it back up and set the timing at 15, shut it down, plug the tps back in, and start out back up and the timing shows it almost dead on the zero mark! Tps unplugged it shows 15 still though. Is it supposed to be at zero with everything plugged in? I'm positive it's the computer retarding the timing. I can Rev the engine and the timing will advance as the RPM goes up but at idle it's at zero... I'm stumped here

[PapaSmurf2k3]

Yeah that's why you unplug the TPS, to take the ECU out of the equation. You are setting base timing.

Also, its supposed to be 20 degrees BTDC, not 15 for the KA24DE. Are you running that, or the KA24E? Might want to double check the FSM just in case.

[MURDERGOON]

Single cam. And I did set it with the tps unplugged. I think I have it figured out. The timing is only at 0 at idle. It jumps up where it should be as soon as you touch the throttle