1989 Mustang GT Keeps dying

the codes refer to system too lean on banks one and two===causes --intake /exhaust leak--MAF/VAF sensors fuel pressures/pump---injectors HO2S ( heated oxygen sensors in the exhaust manifolds before the cat converters
the fuel trim is what the computer sets at after a long term run and not after a few trips around the block
it is the HO2S sensors that control the mixture by reading the exhaust gas composition and reporting to the ECM which adjusts the injector operation
they could be getting a bad reading is the flex section of the exhaust manifold pipe is cracked in side of the braid covering

Hi, Sounds like you have an air intake leak. Most likely a bad gasket on the manifold to the engine block. Replace with new one. Good luck.

You could have either an injector that is stuck open or a fuel pressure regulator that has developed a leak. A leaky injector will usually only leak fuel into one cylinder as it is located just above the intake valve in the lower part of the intake while a leaky fuel pressure regulator will leak fuel into the front end of the intake manifold [behind the throttle plates] and the fuel will acuumulate throughout the upper intake plenum. When a fuel pressure regulator develops a leak the fuel that is escaping from it flows through the small 1/8" diameter plastic vacuum line which goes from the top of the regulator to the intake manifold. Even a trace of fuel in this line means the regulator is bad. I've seen both leak items leak but probably replace 10 regulators leak for every one injector. Good luck, hope you find your problem!

It under the plastic upper intake plenum connected to the CFI assembly.


Fuel Pressure RegulatorREMOVAL & INSTALLATION
(see Figure 1)

1. Disconnect the negative battery cable.
2. Relieve fuel system pressure.
3. Disconnect the ignition coil.
4. Remove the upper intake manifold.
5. Disconnect the vacuum line to the regulator.
6. Remove the snapring from the regulator housing.
7. Place a towel under the regulator to absorb any spilled fuel and remove the pressure regulator from the fuel rail socket.
8. Remove the pressure regulator from the fuel rail.
9. Remove the pressure regulator O-ring filter, O-ring backup and O-ring and discard them.
   

Fig. 1: Exploded view of the pressure regulator assembly-MFI systems


To install:

1. Before installing the O-rings, lubricate them with clean engine oil and install them on the regulator inlet as a complete assembly.
2. Install the snapring retainer into the slot on the regulator housing.
3. Connect the vacuum line to the regulator.
   

Ensure that the retainer is properly seated in the slot in the regulator housing. Pull on the regulator to make sure that it is properly seated.

1. Connect the negative battery cable.
2. Turn the ignition ON for 2 seconds and then turn it OFF for 10 seconds. Again turn the ignition ON and check for leaks.
3. Install the manifold plenum.

Good luck; TY for using Fixya (remember rated this post)

This is for a 1989 Ford F150 In-Line 6-Cylinder (4.9L) wrongly posted by the Asker under a 1986 Ford Mustang....

Fuel Injector Pressure Regulator. Look it up on line at any of the reputable auto parts websites to get an idea what it looks like.
There should be a Rubber Vacuum Line coming from this (the Regulator is located on the Fuel Line prior to the Fuel Injectors) to the Intake. Take this Line OFF. If there is gas in that line = The Fuel Injector Pressure Regulator diaphram is broken and the Fuel is being dumped into the Intake and NOT being advanced onto the Fuel Injectors; and the Regulator must be replaced.
Let me know if this helped.

For 2000 Chevrolet Truck Blazer 4WD 4.3L SFI 6cyl
If your engine is a 4.3L V-6 with CPI (central point injection) it is inside the upper intake manifold. The upper intake manifold is bolted on top of the normal intake manifold.

The throttle body is mounted on it and your fuel lines terminate into the center of this.


Removal & Installation

1. Relieve the fuel system pressure.
2. Remove the air cleaner outlet resonator.
3. Disconnect the engine wiring harness from the retaining clips at the front of the engine.
4. Disconnect the fuel pressure regulator vacuum line.
5. Clean any dirt from the fuel pressure regulator and the surrounding area.
6. Disconnect the fuel return pipe.
7. Remove the fuel return pipe retainer.
8. Remove the fuel pressure regulator retainer.
9. Remove the fuel pressure regulator.
10. Inspect the regulator filter screen for contamination. If contaminated, replace the fuel pressure regulator.

To install:



Fig. Fuel pressure regulator-4.2L engine

1. Install the regulator filter.
2. Install the new O-ring on the fuel pressure regulator.
3. Lubricate the fuel pressure regulator O-ring with clean engine oil.
4. Push the fuel pressure regulator into the regulator housing on the fuel rail.
5. Install the fuel pressure regulator retainer. Tighten the regulator retainer screw to 71 inch lbs. (8 Nm).
6. Install the fuel return pipe retainer. Tighten the return pipe retainer screw to 71 inch lbs. (8 Nm).
7. Connect the fuel return pipe.
8. Connect the fuel pressure regulator vacuum line.
9. Connect the negative battery cable.
10. Inspect for leaks:
    1. Turn ON the ignition for 2 seconds.
    2. Turn OFF the ignition for 10 seconds.
    3. Turn ON the ignition.
    4. Inspect for fuel leaks.
11. Install the engine wiring harness into the retaining clips at the front of the engine.
12. Install the air intake resonator.

Hope help with this (remember rated this post).

it's your upper intake manifold gasket. it has a crack in it and needs to be replaced. your getting to much air and not enough gas. mine did the same thing.

Did you have the computer reflashed for the new injectors? If not, you have to do so. I don't know how much bigger than stock your new fuel injectors are but if it's more than just a little bigger, and you don't reprogram the computer, your mixture is going to be way too rich and you'll be stumbling. Have the ECU reprogrammed to properly control the injectors - many modifications don't affect, or are not affected by, the ECU, but injectors aren't on that list. If you did reprogram it, it may be simply because larger injectors aren't as precise when flowing slowly or at small duty cycles. There's also the chance that one or more are leaking slightly although that's not as common.

The BBK SSI manifolds have a bunch of issues - google it to see. But I would suggest you set your idle and TPS sensor and see how it runs.

I recommend you check the fuel pressure regulator diaphragm for proper installation and tears. Did you get a new one with your rebuild kit?