KOER 91 with Intake Install... Problem number 4?

[crunchie12268]

well this is problem for or 5 with this install... but if anybody doesn't know, I installed a cobra intake in place of my Trick Flow Street Heat. Well, I finally get the damn stripped bolt out and get the thing up and running. It sounds good, still idles like ****.....

anyways, I cruise down the road and notice I am not leaking any coolant or fuel. I look at my a/f gauge and notice that it just kinda dies down, pretty soon it reads nothing, ( I have the gauge that uses the little lights, it is from autometer, taps into the o2). Pretty soon my check engine light comes on and I head to Oreily's to get the codes read. Up comes KOER 91 which says something like Oxygen Gas Sensor Malfunction or Fuel system running lean etc.

I get back home and check the fuel pressure with the vaccuum on and it reads 30psi. I crank it up some more to 34, 35, 36 and nothing happens on my a/f gauge. It doesn't even read anything but on initial startup it read four or five bars lean.... it will creep up to stoich but just dies again. So, I was just wondering what you guys think? Do you think it is the 02's? Any suggestions would really help because this is keeping me unable to drive to work. It sucks

 

[crunchie12268]

please?

 

[stang22]

I copied this from one of jrichker's previous replies to a 91. Good stuff!

Tim

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 is in the wiring harness for the fuel injection wiring. I grounded mine to one of the intake manifold bolts