How best to deal with old fuel injectors

[emuskovitz]

Since I got it my 300zx (an 87 N/A) has been slowly losing power over time. It runs smoothly, but it feels like it has no torque behind it anymore, and the engine has to really work to get up into the higher RPM's. You actually can't get it above 70mph anymore without downshifting into third. I've checked it for vacuum leaks, I'm confident it has none. Fuel pressure to the injector rail is fine at well. I put in a new mass airflow sensor too, which got the car running smoothly, but didn't fix the power deficit. My current theory is that it's an issue with the injector output, especially since there's a hint of white smoke in the exhaust and it comes out hot as hell. It burns a hole in my lawn if I park it on the grass. My question is about the different options available for cleaning the injectors. I can either run liquid injector cleaner through the fuel system, take the injectors out and clean them individually or I can replace them altogether. Would there be a notable difference between cleaning then by hand and just running injector cleaner? Would getting new ones be likely to make a significant difference over cleaning the existing ones? This isn't something I have a lot of experience with so any input is appreciated.

[ca18det_boy]

I would either replace them completely, or you can send them out to a company to get cleaned and flow tested.

[centralcoaster33]

New, flow matched set = Best

However, I don't have as much information as you to come to the conclusion that injectors are indeed faulty and/ or the source of your power loss. Have you inspected them? Checked resistance? Checked voltage and ground wires? Checked spray pattern? I know sometimes people do all of the above before replacing parts. The FSM probably has some inspection ideas in it. Vacuum leak is a potential issue, so I'm hoping your confidence in that is valid. Timing is important also, so Crank and Cam angel sensors I've read about with these cars. That and spark strength I think.

Have you checked the ECU for codes? Might be some clues in there. Like if an O2 sensor is out of range or something.

Good luck!

[emuskovitz]

I haven't had time to remove the injectors and inspect them yet, I plan to do it at the same time I replace the spark plugs. Since the first post I have started running injector cleaner with the fuel, and will say it makes a very notable difference. The ECU has no codes at this point but that doesn't mean there isn't a bad sensor, sometimes they slip by without triggering anything. The cam and crank sensors are a good idea though, and might be worth replacing just to be safe.

[evildky]

Could also be as simple as bad plugs or plug wires, perhaps even the distributor cap or rotor button.