Electrical Code 91. Replaced O2's. Now Code 41. Runs Rich.

Discussion in 'Fox 5.0 Mustang Tech' started by JohnnyK81, Sep 29, 2013.


  1. JohnnyK81

    JohnnyK81 Member

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    So as the title said, was getting code 91 with KOER. Replaced O2's, now get code 41.

    No need to post the test path, already did that.

    Here is what I found. When the car is cold and i probe the computer pins for the O2 sensors, it starts at 4.xx volts?? Then slowly drops to 0.3-6ish volts after a couple minutes. You can start it, it will start at 4.xx volts, and you can watch it drop.

    Any ideas?
     
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  2. Mustang5L5

    Mustang5L5 Car used in adult film "Highway Gangbang-InDaButt"
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    http://www.stangnet.com/mustang-forums/threads/koer-code-41.573573/

    Post 4 and 5 have good info.


    First thing I'd do is swap the o2 sensors, erase the codes and rerun them after some driving time. The code 41 should become a code 91. That will help to determine of the issue is sensor related, or if it's wiring related or elsewhere.
     
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  3. JohnnyK81

    JohnnyK81 Member

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    Ehh thanks man.. Well both O2's are new, so, I'm not sure.. Suppose I could try though.

    Yeah, I read through those posts.. Gave the engine a healthy squirting with brake clean while running. I really couldn't find anything.

    No tubes on the back of engine. Most emissions removed (Crammed in a 1967). Which brings to me to the fact that KOER also threw a code 33.. Any bearing, or completely unrelated? (Obviously, EGR won't be opening).

    I remember plugging the holes on the back of the heads with some standard bolts and some sealant.
     
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  4. Mustang5L5

    Mustang5L5 Car used in adult film "Highway Gangbang-InDaButt"
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    I know swapping new o2s around sounds redundant, but it will exclude if the issue is the sensor itself, or elsewhere. After all, swapping new o2s in caused the code to jump sides in the first place. Don't want you to chase your tail for a bad sensor

    Code 41 is lean.

    EGR code 33 disables the EGR function, so it won't pull fuel. As long as you don't have one of those resistors tricking the car into thinking the EGR is working, this shouldn't be the cause.
     
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  5. JohnnyK81

    JohnnyK81 Member

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    Ooh, well i did make up some EGR resistor doodad quite a few years ago that plugs into the EFI harness egr vacuum solenoid?
     
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  6. JohnnyK81

    JohnnyK81 Member

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    Ok, a few things.

    Found a very small vacuum leak on a rubber plug on the back of the intake.. BUT, I might have cracked it right now while I was messing around back there, AND, I'm not sure how small of a vacuum leak is required to run lean.. especially in only 1 bank?

    Secondly, pulled off my resistor thingy, and fired up the car. Immediate CEL. Code 31 (KOEO).

    Will removing the resistor pack from the EGR cause a CEL? I thought all EGR codes didn't display on the CEL until you ran the codes? (So with that pack removed, KOEO codes are 31, 81, 82, 84, 85).
     
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  7. Mustang5L5

    Mustang5L5 Car used in adult film "Highway Gangbang-InDaButt"
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    That one code is one of the 13 or so that will trip the light. However it also totally disabled the egr function. During normal operation, the car pulls fuel when the egr is open. Tricking the car into thinking the egr still works will have it pull fuel, but since the egr isn't open, the inert air isn't injected and you run lean at cruise.

    Not saying this is your issue, but if you reset the codes drive and it goes away, you could recreate the problem by putting your resistors back and see of it comes back. This will confirm the issue


    The other codes aren't critical and don't affect how engine runs. Do you still have the 41 when pulling koer?


    Sent from my iPhone 4S using Tapatalk
     
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  8. JohnnyK81

    JohnnyK81 Member

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    Thanks for the help man.

    Swapped O2 sensors.. I also swapped ECU's just because on the 67, I had to hide the ECU under the dash so I can't probe it. So I threw on an a9p so I can have it sitting on the seat. Not a great idea to change so many variables, but I'll run the KOER again later this week with the original CPU to check.. But I wanted to probe the O2 sensors (one switches back between .1 and .8 it seems.. the other one stays around .1-.2? Could be bad, not sure... BUT

    Ran KOER again. I ended up with these.

    33 - EGR Valve Opening Not Detected (M,R)

    94 - Secondary Air Injection Inoperative. bank two, driver side (R), Torque Converter Clutch Solenoid Circuit Failure (O) (I guess it's the first one. But you'd think i'd get a KOEO 94 because it's an a9p in a manual car? But I didn't)
    44 - Secondary Air System Inoperative. bank one, passenger side (R)

    Still smells horribly rich though. But the lean code has gone away for now it seems?? Maybe when I put the other ECU back in it will reappear later this week (Only get to drive it rarely).

    I'm still iffy on this EGR stuff though.. You are saying it will make it dump fuel?

    Should I put resistors on the other EGR stuff too.. Or remove the resistors from everything? Just hate to drive around with the light on, but don't want to run rich!
     
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  9. jrichker

    jrichker StangNet's favorite TOOL
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    Here's an update to the post you were referred to earlier...

    Code 41 or 91 Three digit code 172 or 176 - O2 sensor indicates system lean. Look for a vacuum leak or failing O2 sensor.

    Revised 29-Sep-2013 to add back in a clogged crossover tube as cause for code 41

    Code 41 is a RH side sensor, as viewed from the driver's seat.
    Code 91 is the LH side sensor, as viewed from the driver's seat.

    Code 172 is the RH side sensor, as viewed from the driver's seat.
    Code 176 is the LH side sensor, as viewed from the driver's seat.

    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

    Testing the O2 sensors 87-93 5.0 Mustangs
    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.

    Disconnect the O2 sensor from the harness and use the body side O2 sensor harness as the starting point for testing. Do not measure the resistance of the O2 sensor , you may damage it. Resistance measurements for the O2 sensor harness are made with one meter lead on the O2 sensor harness and the other meter lead on the computer wire or pin for the O2 sensor.

    Backside view of the computer wiring connector:
    [​IMG]

    87-90 5.0 Mustangs:
    Computer pin 43 Dark blue/Lt green – LH O2 sensor
    Computer pin 29 Dark Green/Pink – RH O2 sensor
    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 voltage should switch between .2-.9 volt at idle.

    91-93 5.0 Mustangs:
    Computer pin 43 Red/Black – LH O2 sensor
    Computer pin 29 Gray/Lt blue – RH O2 sensor
    The computer pins are 29 (LH O2 with a Gray/Lt blue wire) and 43 (RH O2 with a Red/Black wire). Use the ground next to the computer to ground the voltmeter. The O2 sensor voltage should switch between .2-.9 volt at idle.


    Testing the O2 sensors 94-95 5.0 Mustangs
    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 red/black wire) and 27 (RH O2 with a gray/lt blue wire). Use pin 32 (gray/red wire) to ground the voltmeter. The O2 sensor voltage should switch between .2-.9 volt at idle.


    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.

    Testing the O2 sensor wiring harness
    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. Using the Low Ohms range (usually 200 Ohms) you should see less than 1.5 Ohms.

    87-90 5.0 Mustangs:
    Computer pin 43 Dark blue/Lt green – LH O2 sensor
    Computer pin 29 Dark Green/Pink – RH O2 sensor
    Disconnect the connector from the O2 sensor and measure the resistance:
    From the Dark blue/Lt green wire in the LH O2 sensor harness and the Dark blue/Lt green wire on the computer pin 43
    From the Dark Green/Pink wire on the RH Os sensor harness and the Dark Green/Pink wire on the computer pin 43

    91-93 5.0 Mustangs:
    Computer pin 43 Red/Black – LH O2 sensor
    Computer pin 29 Gray/Lt blue – RH O2 sensor
    Disconnect the connector from the O2 sensor and measure the resistance:
    From the Red/Black wire in the LH O2 sensor harness and the Red/Black wire on the computer pin 43
    From the Dark Green/Pink Gray/Lt blue wire on the RH Os sensor harness and the Gray/Lt blue wire on the computer pin 29

    94-95 5.0 Mustangs:
    Computer pin 29 Red/Black – LH O2 sensor
    Computer pin 27 Gray/Lt blue – RH O2 sensor
    From the Red/Black wire in the LH O2 sensor harness and the Red/Black wire on the computer pin 29
    From the Dark Green/Pink Gray/Lt blue wire on the RH Os sensor harness and the Gray/Lt blue wire on the computer pin 27

    There is a connector between the body harness and the O2 sensor harness. Make sure the connectors are mated together, the contacts and wiring are not damaged and the contacts are clean and not coated with oil.

    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

    Make sure you have the proper 3 wire O2 sensors. Only the 4 cylinder cars used a 4 wire sensor, which is not compatible with the V8 wiring harness.

    Replace the O2 sensors in pairs if replacement is indicated. If one is weak or bad, the other one probably isn't far behind.

    Code 41 can also be due to carbon plugging the driver’s side Thermactor air crossover tube on the back of the engine. The tube fills up with carbon and does not pass air to the driver’s side head ports, Remove the tube and clean it out so that both sides get good airflow: this may be more difficult than it sounds. You need something like a mini rotor-rooter to do the job because of the curves in the tube. Something like the outer spiral jacket of a flexible push-pull cable may be the thing that does the trick.

    If you get only code 41 and have changed the sensor, look for vacuum leaks. This is especially true if you are having idle problems. The small plastic tubing is very brittle after many years of the heating it receives. Replace the tubing and check the PVC and the hoses connected to it.



    Some basic theory to clarify how things work is in order…

    EGR System theory and testing

    Revised 29-Sep-2013 to add code definitions for EGR sensor and EVR regulator.

    The EGR shuts off at Wide Open Throttle (WOT), so it has minimal effect on performance. The addition of exhaust gas drops combustion temperature, increases gas mileage and reduces the tendency of the engine to ping. It can also reduce HC emissions by reducing fuel consumption. The primary result of EGR usage is a reduction in NOx emissions. It does this by reducing the amount of air/fuel mixture that gets burned in the combustion process. Less air from the intake system means less air to mx with the fuel, so the computer leans out the fuel delivery calculations to balance things out. This reduces combustion temperature, and the creation of NOx gases. The reduced combustion temp reduces the tendency to ping.

    The computer shuts down the EGR system when it detects WOT (Wide Open Throttle), so the effect on full throttle performance is too small to have any measurable negative effects.

    The EGR system has a vacuum source (line from the intake manifold) that goes to the EVR, computer operated electronic vacuum regulator. The EVR is located on the back of the passenger side shock strut tower. The computer uses RPM, Load. and some other factors to tell the EVR to pass vacuum to open the EGR valve. The EGR valve and the passages in the heads and intake manifold route exhaust gas to the EGR spacer (throttle body spacer). The EGR sensor tells the computer how far the EGR valve is open. Then computer adjusts the signal sent to the EVR to hold, increase or decrease the vacuum. The computer adds spark advance to compensate for the recirculated gases and the slower rate they burn at.

    The resistor packs used to fool the computer into turning off the CEL (Check Engine Light) off are a bad idea. All they really do is mess up the data the computer uses to calculate the correct air/fuel mixture. You can easily create problems that are difficult to pin down and fix.

    [​IMG]

    Troubleshooting:
    There should be no vacuum at the EGR valve when at idle. If there is, the EVR (electronic vacuum regulator) mounted on the backside of the passenger side wheelwell is suspect. Check the vacuum line plumbing to make sure the previous owner didn’t cross the vacuum lines.

    Diagram courtesy of Tmoss & Stang&2birds. (the diagram says 88 GT, but the EGR part is the same for 86-93 Mustangs)
    [​IMG]

    The EGR sensor is basically a variable resistor, like the volume control on a radio. One end is 5 volt VREF power from the computer (red/orange wire). One end is computer signal ground (black/white), and the middle wire (brown/lt green) is the signal output from the EGR sensor. It is designed to always have some small voltage output from it anytime the ignition switch is the Run position. That way the computer knows the sensor & the wiring is OK. No voltage on computer pin 27 (brown/lt green wire) and the computer thinks the sensor is bad or the wire is broken and sets code 31. The voltage output can range from approximately .6-.85 volt. A defective or missing sensor will set codes 31 (EVP circuit below minimum voltage) or 32 ( EGR voltage below closed limit).

    The EVR regulates vacuum to the EGR valve to maintain the correct amount of vacuum. The solenoid coil should measure 20-70 Ohms resistance. The regulator has a vacuum feed on the bottom which draws from the intake manifold. The other vacuum line is regulated vacuum going to the EGR valve. One side of the EVR electrical circuit is +12 volts anytime the ignition switch is in the run position. The other side of the electrical circuit is the ground path and is controlled by the computer. The computer switches the ground on and off to control the regulator solenoid. A defective EVR will set codes 33 (insufficient flow detected), 84 (EGR Vacuum Regulator failure – Broken vacuum lines, no +12 volts, regulator coil open circuit, missing EGR vacuum regulator.)


    EGR test procedure courtesy of cjones

    To check the EGR valve:
    Bring the engine to normal temp.

    Connect a vacuum pump to the EGR Valve or see the EGR test jig drawing below. Connnect the test jig or to directly to manifold vacuum.

    Do not connect the EGR test jig to the EVR (Electronic Vacuum Regulator).


    Apply 5in vacuum to the valve. Using the test jig, use your finger to vary the vacuum

    If the engine stumbled or died then EGR Valve and passage(there is a passageway through the heads and intake) are good.

    If the engine did NOT stumble or die then either the EGR Valve is bad and/or the passage is blocked.

    If the engine stumbled, connect EGR test jig to the hose coming off of the EGR Valve.
    Use your finger to cap the open port on the vacuum tee.
    Snap throttle to 2500 RPM (remember snap the throttle don't hold it there).
    Did the vacuum gauge show about 2-5 in vacuum?
    If not the EVR has failed

    EGR test jig
    [​IMG]

    To test the computer and wiring to the computer, you can use a test light across the EVR wiring connectors and dump the codes. When you dump the codes, the computer does a self test that toggles every relay/actuator/solenoid on and off. When this happens, the test light will flicker. If the test light remains on the computer or the wiring is suspect.

    To check the EVR to computer wiring, disconnect the EVR connector and connect one end of the Ohmmeter to the dark green wire EVR wiring. Remove the passenger side kick panel and use a 10 MM socket to remove the computer connector from the computer. Set the Ohmmeter to high range and connect the other ohmmeter lead to ground. You should see an infinite open circuit indication or a reading greater than 1 Meg Ohm. If you see less than 200 Ohms, the dark green wire has shorted to ground somewhere.



    Thermactor Air System
    Some review of how it works...

    Revised 17-Sept-2011 to add testing procedure.

    The Thermactor air pump (smog pump) supplies air to the heads or catalytic converters. This air helps break down the excess HC (hydrocarbons) and CO (carbon monoxide). The air supplied to the catalytic converters helps create the catalytic reaction that changes the HC & CO into CO2 and water vapor. Catalytic converters on 5.0 Mustangs are designed to use the extra air provided by the smog pump. Without the extra air, the catalytic converters will clog and fail.

    The Thermactor air pump draws air from an inlet filter in the front of the pump. The smog pump puts air into the heads when the engine is cold and then into the catalytic converters when it is warm. The Thermactor control valves serve to direct the flow. The first valve, TAB (Thermactor Air Bypass) or AM1 valve) either dumps air to the atmosphere or passes it on to the second valve. The second valve, TAD (Thermactor Air Diverter valve or AM2 valve) directs it to the heads or the catalytic converters. Check valves located after the TAB & TAD solenoids prevent hot exhaust gases from damaging the control valves or pump in case of a backfire. The air serves to help consume any unburned hydrocarbons by supplying extra oxygen to the catalytic process. The computer tells the Thermactor Air System to open the Bypass valve at WOT (wide open throttle) minimizing engine drag. This dumps the pump's output to the atmosphere, and reduces the parasitic drag caused by the smog pump to about 2-4 HP at WOT. The Bypass valve also opens during deceleration to reduce or prevent backfires.

    Code 44 RH side air not functioning.
    Code 94 LH side air not functioning.

    The computer uses the change in the O2 sensor readings to detect operation of the Thermactor control valves. When the dump valve opens, it reduces the O2 readings in the exhaust system. Then it closes the dump valve and the O2 readings increase. By toggling the dump valve (TAB), the computer tests for the 44/94 codes.

    Failure mode is usually due to a clogged air crossover tube, where one or both sides of the tube clog with carbon. The air crossover tube mounts on the back of the cylinder heads and supplies air to each of the Thermactor air passages cast into the cylinder heads. When the heads do not get the proper air delivery, they set codes 44 & 94, depending on which passage is clogged. It is possible to get both 44 & 94, which would suggest that the air pump or control valves are not working correctly, or the crossover tube is full of carbon or missing.


    [​IMG]


    Computer operation & control for the Thermactor Air System
    Automobile computers use current sink technology. They do not source power to any relay, solenoid or actuator like the IAC, fuel pump relay, or fuel injectors. Instead the computer provides a ground path for the positive battery voltage to get back to the battery negative terminal. That flow of power from positive to negative is what provides the energy to make the IAC, fuel pump relay, or fuel injectors work. No ground provided by the computer, then the actuators and relays don't operate.

    One side of the any relay/actuator/solenoid in the engine compartment will be connected to a red wire that has 12-14 volts anytime the ignition switch is in the run position. The other side will have 12-14 volts when the relay/actuator/solenoid isn't turned on. Once the computer turns on the clamp side, the voltage on the computer side of the wire will drop down to 1 volt or less.

    In order to test the TAD/TAB solenoids, you need to ground the white/red wire on the TAB solenoid or the light green/black wire on the TAD solenoid.

    For 94-95 cars: the colors are different. The White/Red wire (TAB control) is White/Orange (Pin 31 on the PCM). The Green/Black wire (TAD control) should be Brown (pin 34 at the PCM). Thanks to HISSIN50 for this tip.

    Testing the system:

    To test the computer, you can use a test light across the TAB or TAD wiring connectors and dump the codes. When you dump the codes, the computer does a self test that toggles every relay/actuator/solenoid on and off. When this happens, the test light will flicker.

    Disconnect the big hose from smog pump: with the engine running you should feel air output. Reconnect the smog pump hose & apply vacuum to the first vacuum controlled valve: Its purpose is to either dump the pump's output to the atmosphere or pass it to the next valve.

    The next vacuum controlled valve directs the air to either the cylinder heads when the engine is cold or to the catalytic converter when the engine is warm. Disconnect the big hoses from the back side of the vacuum controlled valve and start the engine. Apply vacuum to the valve and see if the airflow changes from one hose to the next.

    The two electrical controlled vacuum valves mounted on the rear of the passenger side wheel well turn the vacuum on & off under computer control. Check to see that both valves have +12 volts on the red wire. Then ground the white/red wire and the first solenoid should open and pass vacuum. Do the same thing to the light green/black wire on the second solenoid and it should open and pass vacuum.

    Remember that the computer does not source power for any actuator or relay, but provides the ground necessary to complete the circuit. That means one side of the circuit will always be hot, and the other side will go to ground or below 1 volt as the computer switches on that circuit.

    The computer provides the ground to complete the circuit to power the solenoid valve that turns the
    vacuum on or off. The computer is located under the passenger side kick panel. Remove the kick panel & the cover over the computer wiring connector pins. Check Pin 38 Solenoid valve #1 that provides vacuum to the first Thermactor control valve for a switch from 12-14 volts to 1 volt or less. Do the same with pin 32 solenoid valve #2 that provides vacuum to the second Thermactor control valve. Starting the engine with the computer jumpered to self test mode will cause all the actuators to toggle on and off. If after doing this and you see no switching of the voltage on and off, you can start testing the wiring for shorts to ground and broken wiring. An Ohm check to ground with the computer connector disconnected & the solenoid valves disconnected should show open circuit between the pin 32 and ground and again on pin 38 and ground. In like manner, there should be less than 1 ohm between pin 32 and solenoid valve #2 and pin 38 & Solenoid valve #1.

    If after checking the resistance of the wiring & you are sure that there are no wiring faults, start looking at the solenoid valves. If you disconnect them, you can jumper power & ground to them to verify operation. Power & ground supplied should turn on the vacuum flow, remove either one and the vacuum should stop flowing.

    Typical resistance of the solenoid valves is in the range of 20-70 Ohms.

    Theory of operation:
    Catalytic converters consist of two different types of catalysts: Reduction and Oxidation.
    The Reduction catalyst is the first converter in a 5.0 Mustang, and the Oxidation converter is the second converter. The Oxidation converter uses the extra air from the smog pump to burn the excess HC. Aftermarket converters that use the smog pump often combine both types of catalysts in one housing. Since all catalytic reactions depend on heat to happen, catalytic converters do not work as efficiently with long tube headers. The extra length of the long tubes reduces the heat available to operate the O2 sensors and the catalytic converters. That will cause emissions problems, and reduce the chances of passing an actual smog test.


    Now for the Chemistry...
    "The reduction catalyst is the first stage of the catalytic converter. It uses platinum and rhodium to help reduce the NOx emissions. When an NO or NO2 molecule contacts the catalyst, the catalyst rips the nitrogen atom out of the molecule and holds on to it, freeing the oxygen in the form of O2. The nitrogen atoms bond with other nitrogen atoms that are also stuck to the catalyst, forming N2. For example:

    2NO => N2 + O2 or 2NO2 => N2 + 2O2

    The oxidation catalyst is the second stage of the catalytic converter. It reduces the unburned hydrocarbons and carbon monoxide by burning (oxidizing) them over a platinum and palladium catalyst. This catalyst aids the reaction of the CO and hydrocarbons with the remaining oxygen in the exhaust gas. For example:

    2CO + O2 => 2CO2

    There are two main types of structures used in catalytic converters -- honeycomb and ceramic beads. Most cars today use a honeycomb structure." Quote courtesy of How Stuff Works (HowStuffWorks "Catalysts")

    What happens when there is no extra air from the smog pump...
    As engines age, the quality of tune decreases and wear causes them to burn oil. We have all seem cars that go down the road puffing blue or black smoke from the tailpipe. Oil consumption and poor tune increase the amount of HC the oxidation catalyst has to deal with. The excess HC that the converters cannot oxidize due to lack of extra air becomes a crusty coating inside the honeycomb structure. This effectively reduces the size of the honeycomb passageways and builds up thicker over time and mileage. Continuous usage under such conditions will cause the converter to fail and clog. The extra air provided by the Thermactor Air System (smog pump) is essential for the oxidation process. It oxidizes the added HC from oil consumption and poor tune and keeps the HC levels within acceptable limits.

    Newer catalytic converters do not use the Thermactor Air System (smog pump) because they are designed to work with an improved computer system that runs leaner and cleaner
    They add an extra set of O2 sensors after the catalytic converters to monitor the oxygen and HC levels. Using this additional information, the improved computer system adjusts the air/fuel mixture for cleaner combustion and reduced emissions. If the computer cannot compensate for the added load of emissions due to wear and poor tune, the catalytic converters will eventually fail and clog. The periodic checks (smog inspections) are supposed to help owners keep track of problems and get them repaired. Use them on an 86-95 Mustang and you will slowly kill them with the pollutants that they are not designed to deal with.
     
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    Last edited: Sep 29, 2013
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  10. JohnnyK81

    JohnnyK81 Member

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    THanks guys.. As I said, no emissions stuff is mounted. Tried to get the egr on there, but absolutely no room (Everything then hits the shock tower).

    So could using this resistor cause a horribly rich smell (And terrible gas mileage, to the tune of 12 or so mpg).. What is i put resistors on EVERYTHING. If I put resistors on nothing, CEL stays on all the time. I don't want to do that. I do not have a chip for a custom tune just to turn off CEL either. I think I removed most of the wiring as well, so I can't just plug in the solenoids and let them hang..
     
    #10
  11. Mustang5L5

    Mustang5L5 Car used in adult film "Highway Gangbang-InDaButt"
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    No. I've seen disabled EGR setup a before and they usually don't cause the symptoms you are describing.

    For the sake of trouble-shooting, leave the resistors off for now.

    Is the rich condition since removing the resistors and changing ecu?
     
    #11
  12. JohnnyK81

    JohnnyK81 Member

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    Nah, rich condition is ever since I got this 67 in a driveable state. :D Only put 400 miles on it so far.
    Good point about the trouble shooting.

    Background.. Couple weeks ago I posted about a code 66 and 98 (think it was 98).. Troubleshooted everything, replaced the MAF.. Code 66 went away to be replaced with a code 91.

    Bought new O2's, then code 41.

    Found that little vacuum leak from a cracked rubber plug on the back of the intake. Not sure if I caused it today or what.. Probably not.. Replugged it.. Idled up to temp and ran KOER.. (I know not the greatest way to warm it up, but I can't drive it until later this week).

    Now the code 44, 94, and 33.

    The other thing I thought of, is when removing the EGR.. I left the middle hole on the lower intake open going to the upper intake.. but I seem to remember probing it and looking with a flashlight and it appeared to go nowhere?
     
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  13. Mustang5L5

    Mustang5L5 Car used in adult film "Highway Gangbang-InDaButt"
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    Middle hole in intake goes to the heads. The gases come up from there into the intake.


    Do you have cats on the car? Is the fuel economy crap?

    Code 94 and 44 are related to the smog pump. But they won't cause the cel nor do they affect how the car runs. There are resistor diagrams to eliminate these codes and they can be used.

    If you drive for a bit and the only codes are those, you can try reinstalling the EGR resistor. But it tends to cause a lean condition at part throttle. Best method to remove it is a tune, if you even get your combo to a point you decide on a custom tune, keep this in mind to delete the EGR function totally from the ecu setup
     
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  14. JohnnyK81

    JohnnyK81 Member

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    No cats (67).. Fuel economy is TERRIBLE.. Stink of gas... In fat, I smell like fuel and exhaust after driving it. haha Let's say, 12mpg ballpark off the top of my head.

    So your suggestion is, unplug EGR resistors.. Let the CEL come on for code 33, drive it for a bit and see how it is now?

    So, when I removed EGR, I remember I made a 3/8" or so plate out of aluminum so the throttle cable would have a place to bolt to.

    I plugged the thermactor bolts in the back of the head (1 on each side if I remembe.r. was a few years ago). I believe that is all I did to remove the EGR.

    So that hole in the intake could be why my upper intake manifold is quite hot to the touch? Could having that still unplugged cause a rich or lean condition?

    Anything else i forgot to plug?
     
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  15. Mustang5L5

    Mustang5L5 Car used in adult film "Highway Gangbang-InDaButt"
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    That could be just the lack of cats. I know I put them back on my car because I hated my clothes smelling like gas. I also get around 15 mpg simply because of how I drive my car.

    That port in the center of the intake is connected to the heads and heat will travel into the intake. There are two ways to block this off "better"

    One is to take a razor blade, or another thin piece of metal and rtv it over the center circular port on top of the lower intake. These ports
    [​IMG]

    Another method is to block it off with the same method at the heads. On the bottom of the lower on one side only the intake will connect to one head. The other is already blocked off. You can block it here. There are actually gasket kits that block this port as well

    Here's a good shot of under the intake. The small port in the center is where the EGR gases travel out of the head and intake the intake. You can block at the head
    [​IMG]

    Will this solve your issue? No, but will help reduce some heat in the upper. Right now you technically haven't deleted the EGR. You just prevent it from flowing.
     
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  16. JohnnyK81

    JohnnyK81 Member

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    THanks man! Definitely not pulling heads/lower intake, so I'll just plug the middle hole. Was hoping to drill and tap, but I suppose doesn't matter what i use!

    BUt how haven't I deleted it? EGR spacer is removed and replaced with a plate so the throttle can bolt up. I HAD to be deleted, so I know it's deleted.. :D But what do you mean exactly?
     
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  17. Mustang5L5

    Mustang5L5 Car used in adult film "Highway Gangbang-InDaButt"
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    Well, for most people deleting the EGR, they do it too keep the intake cool. So they block the ports. But the gases are still present in the intake manifold. So they don't really accomplish their goal

    Your situation is different where it just wouldn't fit.

    Most fox mustang guys think it adds HP.

    Needless to say, I don't think the EGR is the source of your issue.
     
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  18. JohnnyK81

    JohnnyK81 Member

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    Ahh, you're probably right.. No, not trying to gain HP.. ;) Wouldn't think it would. It would be ideal if I could keep it, but as I said, on a 67, the intake tube runs straight into the RH shock tower, unfortunately.

    No, probably not the source of my problem, but could be the source of my extremely hot upper intake?

    I will leave the resistors off and drive it for a couple hours this week then recheck codes and see where we are at!

    Thanks!
     
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  19. jrichker

    jrichker StangNet's favorite TOOL
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    The 94-95 5.0 Mustangs and 95-97 5.0 Explorers use an adapter/spacer that has a 45 degree angle that might be a good fit for you
     
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