Just after upgrading from 19's to 24lb injectors

That combo is fairly similar to mine. I have no problems with the 24's. I would go through the injector harness and check for proper voltage at each injector. How's the car running?

Trouble codes are either 2 digit or 3 digit, there are no cars that use both 2 digit codes and 3 digit codes.

Codes have different answers if the engine is running from the answers that it has when the engine isn't running. It helps a lot to know if you had the engine running when you ran the test.

The odds are that you got a code 18 or 81.

Code 18 - SPOUT out or wiring fault - look for short to ground in SPOUT wiring going back to the computer. Possible bad TFI.

Code 81 – Secondary Air Injection Diverter Solenoid failure AM2. The solenoid valve located on the back side of the passenger side wheel well is not functional. Possible bad wiring, bad connections, missing or defective solenoid valve. Check the solenoid valve for +12 volts at the Red wire and look for the Lt Green/Black wire to switch from +12 volts to 1 volt or less. The computer controls the valve by providing a ground path on the LT Green/Black wire for the solenoid valve.

With the with the ignition on, look for 12 volts on the red wire on the solenoid connector. No 12 volts and you have wiring problems.

With the engine running, stick a safety pin in the LT Green/Black wire for the solenoid valve & ground it. That should turn the solenoid on and cause air to flow out the port that goes to the pipe connected to the cats. If it doesn't, the valve is bad. If it does cause the airflow to switch, the computer or wiring going to the computer is not signaling the solenoid valve to open.

Putting the computer into self test mode will cause the solenoid valve to toggle. If you listen carefully, you may hear it change states.

Code 35 EVR - EVP sensor signal is/was high – Bad sensor, or possible missing ground for EVR circuit. With the power off, measure the resistance between the black/white wire and battery ground. You should see less than 1 ohm. Check the same black /white wire on the TPS and MAP sensor. More than 1 ohm there and the wire is probably broken in the harness between the engine and the computer. The 10 pin connectors pass the black/white wire back to the computer, and can cause problems.

See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host)

http://www.veryuseful.com/mustang/tech/engine/images/88-91eecPinout.gif

See http://fordfuelinjection.com/index.php?p=6 for more wiring help & 10 pin connector diagrams

Code 42 & 92 (running) System rich - Fuel control or (memory) System was rich for 15 seconds or more (no HO2's switching) - Fuel control. Look for leaking injectors, fuel pressure too high, cylinder(s) not firing due to bad ignition.