Pulled KOER code 91 ...
- Thread starter dubbsix
- Start date
68torinogt
Hey guys, guess what--I have a bi-pass!!!
fuel pumps hum loud and the o2 should fix the problem.
but if you really have a fuel problem fix it first,
but if you really have a fuel problem fix it first,
Well me having a fuel issue is only because the pump is just plain loud when the car is running. I had a similar problem with another car and when i changed the fuel pump it quieted down again. Someone told me the pumps start to hum loud when they are bout to die... is that true?
68torinogt
Hey guys, guess what--I have a bi-pass!!!
68torinogt
Hey guys, guess what--I have a bi-pass!!!
i would see how much they are first. if it is like $10 bucks then i would but if it is like 50 then hell no
68torinogt
Hey guys, guess what--I have a bi-pass!!!
I'd check the signal on the code-throwing O2. Look for proper frequency and amplitude of switching.
If the FP was the issue, chances are you'd see both banks spit an O2 code or none spit the code. Additionally, it would likely ping or drop pressure (as a result of lackluster volume) at WOT.
Good luck.
If the FP was the issue, chances are you'd see both banks spit an O2 code or none spit the code. Additionally, it would likely ping or drop pressure (as a result of lackluster volume) at WOT.
Good luck.
68torinogt
Hey guys, guess what--I have a bi-pass!!!
68torinogt
Hey guys, guess what--I have a bi-pass!!!
generally when a pump is bad you will not be able to even start the car. it shouldnt be the pump at all.
some minor thinks i would start off with is
clean the mass air sensor
change the o2
if problems persist with the stumble then pm me and i will work you thru some more items to check.
does it do anything else?
what year is it?
was it taken care of?
do you have pics?
some minor thinks i would start off with is
clean the mass air sensor
change the o2
if problems persist with the stumble then pm me and i will work you thru some more items to check.
does it do anything else?
what year is it?
was it taken care of?
do you have pics?
89streetbeast
New Member
68torinogt
Hey guys, guess what--I have a bi-pass!!!
Per HISSIN50's recommendation, check the voltage output of the O2 sensor first. At $40 a piece, they are not cheap. It is best to replace them in pairs, because if one is bad, the other is not far from failing.
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. Many times the end result is an engine that runs pig rich and stinks of unburned 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.
Most of the common multimeters have a resistance scale. Be sure the O2 sensors are disconnected and measure the resistance from the O2 sensor body harness to the pins on the computer.
Note that all resistance tests must be done with power off. Measuring resistance with a circuit powered on will give false readings and possibly damage the meter. Do not attempt to measure the resistance of the O2 sensors, it may damage them.
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
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. Many times the end result is an engine that runs pig rich and stinks of unburned 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.
Most of the common multimeters have a resistance scale. Be sure the O2 sensors are disconnected and measure the resistance from the O2 sensor body harness to the pins on the computer.
Note that all resistance tests must be done with power off. Measuring resistance with a circuit powered on will give false readings and possibly damage the meter. Do not attempt to measure the resistance of the O2 sensors, it may damage them.
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
68torinogt
Hey guys, guess what--I have a bi-pass!!!
After 6 years and 10,600+ posts, I have written one in pieces and parts responding to Stangnet posts.
The Probst book I metioned is an important part of a Mustang library. Here's a book that will get you started with how the Ford electronic engine control or "computer" works.
Ford Fuel Injection & Electronic Engine Control 1988-1993 by Charles Probst :ISBN 0-8376-0301-3.
It's about $20 from Borders.com see http://www.amazon.com/ . Select boo...very good, and I found it to be very helpful.
