Have a 91 Z28 with a 305 TPI. Car starts up fine and idles fine. The problem is that when I'm driving (at any speeds) the car seems to loose fuel pressure and cut off/starts puttering (as in it starts to go putt putt). I recently replaced plugs and wires. When I started to notice this I switched out the fuel filter under the car thinking that was the problem. Is that the only fuel filter that this car came out with? I'm now thinking it may be an injector that is dirty or not properly working. I've also resorted to dropping in one of those Lucas fuel cleaner bottles, but that didn't seem to help. Any help would be appreciated.

 

ohm check your injectors. those multecs suck. then call Jon at FIC and buy some Bosch injectors and get back on the raod.. any under 12ohms are no good.

 

Mine did that at low throttle at like 35 an up it would putt and bump like the cars do if you work a clutch to fast, i cahnged plugs and 02 sensor it stoped but it still runs like **** lol

 

plugs were changed not the 02 sensor. I'll try replacing it first before purchasing new injectors.

 

Low fuel pressure will cause your injectors to act as if they are bad. Have you measured the fuel pressure at the fuel rail? If not, that is where I will start. If you have problems with the fuel pressure, then trouble shooting that system is where I would start.
Checking the resistance of all 8 injectors is a good idea, but if it all check out, that doesn't mean that your injectors are fine. You could have leaking injectors, which could be revealed by a fuel pressure decay test. Or you could also have clogged injectors. Using fuel additives and injector cleaners is not going to do much in the way of resolving that problem. Are the injectors loud when the car is running? This can be an indication of them getting worn out?
However, before you start swapping parts out, I would start by taking fuel pressure measurements and going from there.
Also check for any vacuum leaks.
Do you have the same symptoms when the car is cold and running in open loop?

 

Car does it as soon as I take off (cold or hot). How would I go about checking the fuel pressure?

 

To test the fuel pressure you need to get a fuel pressure gauge (I got mine from Autozone for something like $37). It needs to be able to plug into the schrader valve on the fuel rail so you just need to tell them that you need a gauge for multi port fuel injected engines, not the one for a TBI.
the schrader valve is on the passenger side of the fuel rail, just underneath the map sensor. You are going to need to remove the distributor cover and the unbolt the map sensor from the plenum, but don't disconnect it, in order to gain access to the schrader valve.
Connect the gauge to the valve and disconect the vacuum port from the fuel pressure regulator. Turn the key to the on position and watch the fuel pressure rise. You can position the gauge so that you can see it through the window from the driver side. Don't start the car. Pressure should build quickly to about 50 PSI and stay stady for quite some time with the ignition key in the on position. Look for any fuel leaks from the vacuum port of the fuel pressure regulator. Such leaks would indicate a faulty FP regulator.
Reconnect the vacuum line to the fuel pressure regulator and start the car. Fuel pressure should hold steady while the car is idling around 40 - 42 PSI. When you give the car a little bit of gas, the fuel pressure should rise slightly and then drop down slightly, but with the accilirator steadily on, the fuel pressure should hold steady around 40-42PSI.