need help on fuel delivery

[91mustangnick]

i have stock 19lb injectors in my stang.

mods:
box intake manifold with intake spacer, cam, 1.6 rockers, cold air induction, long tube headers with custom exhaust, complete igintion system, pulleys, electric fan and some other tuning.

i was getting a code 41 and 91 lean setting, i have not found no vacume leaks and was woundering if 30lb injectors and a new MAF sensor to match injectors is plenty, im getting them at a cheap price.

and it takes about 3 starts to get it running with out dieing out when cold.

Nick

 

[Black 93 Fox]

30# injectors is wayyyyy to much fuel for your car. You could put thoes on after a H/C/I and still have alot of fuel left over. I would try new 02 sensors if thoes are bad they can screw with the computer and mess up the mixture. Also check out the fuel pump, fuel filter and such.

 

[2002BLGT]

fuel pump 190lph atleast , new fuel filter, injector cleaner , adjustable regulator, and check pressure , might wanna try a new MAF sensor too .....sometimes the cold air kits will mess them up some , 02s are suspect too but I would go in the order I mentioned ,

 

[91mustangnick]

i have new filter, O2 sensors, and a regulator, but i still have stock pump.

 

[jrichker]

Read through the entire post. Take special notice of how to measure the O2 sensor output and compare the recommended readings against what you observe.

Code 41 or 91 - O2 indicates system lean. Look for a vacuum leak or failing O2 sensor.
The computer sees a lean mixture signal coming from the O2 sensors and tries to compensate by adding more fuel.

The following is a Quote from Charles O. Probst, Ford fuel Injection & Electronic Engine control:
"When the mixture is lean, the exhaust gas has oxygen, about the same amount as the ambient air. So the sensor will generate less than 400 Millivolts. Remember lean = less voltage.

When the mixture is rich, there's less oxygen in the exhaust than in the ambient air , so voltage is generated between the two sides of the tip. The voltage is greater than 600 millivolts. Remember rich = more voltage.

Here's a tip: the newer the sensor, the more the voltage changes, swinging from as low as 0.1 volt to as much as 0.9 volt. As an oxygen sensor ages, the voltage changes get smaller and slower - the voltage change lags behind the change in exhaust gas oxygen.

Because the oxygen sensor generates its own voltage, never apply voltage and never measure resistance of the sensor circuit. To measure voltage signals, use an analog voltmeter with a high input impedance, at least 10 megohms. Remember, a digital voltmeter will average a changing voltage." End Quote

Measuring the O2 sensor voltage at the computer will give you a good idea of how well they are working. You'll have to pull the passenger side kick panel off to gain access to the computer connector. Remove the plastic wiring cover to get to the back side of the wiring. Use a safety pin or paper clip to probe the connections from the rear. The computer pins are 29 (LH O2 with a dark green/pink wire) and 43 (RH O2 with a dark blue/pink wire). Use the ground next to the computer to ground the voltmeter.

The O2 sensor ground (orange wire with a ring terminal on it) is in the wiring harness for the fuel injection wiring. I grounded mine to one of the intake manifold bolts