Code 41 and 91

Discussion in 'Fox 5.0 Mustang Tech' started by Haus, Sep 9, 2008.


  1. Haus

    Haus Member

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    my answers or question in bold
  2. joel5.0

    joel5.0 New Member

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    Disconnect line from FPR and while the KOER is running, dip the open vacuum line in a container with some fuel, if the line is too short, attach an extension vacuum hose. As I mentioned, you may have to control how much fuel is allowed to be sucked through the vacuum line/hose, so the engine doesn't stall while the KOER is executed.

    This is to create an obviously "rich" condition, and check how the EEC "reads" it. LUK
  3. jrichker

    jrichker StangNet's favorite TOOL SN Certified Technician Founding Member

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    Joel's idea was to disconnect a vacuum line from the intake manifold and use it to suck gas into the manifold. You may need some way of limiting the flow like kinking the line or bending it so that you don't suck up too much gas and stall the engine.
  4. Haus

    Haus Member

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    ok i did the test and now the only codes that come up are 33/44/94

    but no 41/91
  5. jrichker

    jrichker StangNet's favorite TOOL SN Certified Technician Founding Member

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    Possible vacuum leak...
    Code 33 - Insufficient EGR flow detected.
    Look for vacuum leaks, cracked vacuum lines, failed EGR vacuum regulator. Check to see if you have 10” of vacuum at the EGR vacuum connection coming from the intake manifold. Look for electrical signal at the vacuum regulator solenoid valves located on the rear of the passenger side wheel well. Using a test light across the electrical connector, it should flicker as the electrical signal flickers. Remember that the computer does not source any power, 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.
    Check for resistance between the brown/lt green wire on the EGR sensor and pin 27 on the computer: you should have less than 1.5 ohm.

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

    http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

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


    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
    apply 5in vacuum to the valve.
    if engine stumbled or died then EGR Valve and passage(there is a passageway through the heads and intake) are good.
    if engine did NOT stumble or die then either the EGR Valve is bad and/or the passage is blocked.
    if engine stumbled, connect vacuum gauge to the hose coming off of the EGR Valve
    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, check for manifold vacuum at the EGR vacuum valve.
    if you have manifold vacuum then connect vacuum gauge to the EGR valve side of the vacuum valve and snap throttle to 2500 RPM.
    should read about 2- 5 in vacuum

    The operation of the EGR vacuum regulator can be checked by using a test light applied across the wiring connector. Jumper the computer into self test mode and turn the key on but do not start the engine. You will hear all the actuators (including the EVR vacuum regulator) cycle. Watch for the light to flicker: that means the computer has signaled the EGR vacuum regulator successfully.
  6. Haus

    Haus Member

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    well im thinking the 33/44/94 had to do with doing the test. but the good part is that i dint get the 41/91 when i added fuel that way with that test.
  7. joel5.0

    joel5.0 New Member

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    Looks like the EEC cannot increase the fuel trim without the "aid" of some fuel through a vacuum line. Now the issue is to ID why. Did the engine show the signs of a too rich A/F during the KOER under those conditions? (black smoke, rough idle, etc)

    Things to recheck:

    [​IMG] Exhaust leaks at the headers?
    [​IMG] Fuel pressure over 38-45 psi with vacuum line connected?
    [​IMG] Vacuum leaks? vacuum lines, intake gaskets, no open breathers present, PCV valve operational and sealing, canister purge line connected solenoid/CANP or plugged.
    [​IMG] HEGO ground wire attached to rear of intake manifold stud or cylinder head bolt? (orange wire)
    [​IMG] Correct 19# injectors installed (orange color)?

    If all the above is OK, leave FP gauge connected, search for a flexible section of the fuel return line, pinch the line with a set of locking pliers, and confirm pressure increases to +45 PSI engine idling. If it does, run the KOER again with the fuel pressure at the new higher pressure setting and LUK what codes show up.
  8. Haus

    Haus Member

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    so is my 33 psi at idle with the line connected not good enough??

    and i thought i should mention that the PCV valve is in there and is connected to the grommet good but the grommet comes out of the hole really easy. so maybe its not sealing correctly. i know its not a ford grommet. its one from pepboys. im thinking i should replace the grommet and get a ford piece since i heard they fit nicer and more tight even tho the one i got on here isnt that old and is not hard and briitle yet.

    cause i just pick up the hose from the manifold to the pcv valve and it comes right out along with the grommet
  9. joel5.0

    joel5.0 New Member

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    For the PCV grommet, clean grommet and intake, and a little Ultra-Black works to ensure it seals and it doesn't pop-up. Regarding the FP..... that is what you're going to find out, if the 33 PSI is not enough, the next questions inline is..... why?...... but you need to ID if at 42 or 47 or 50 psi the A/F codes disappear. LUK
  10. hotcobra03

    hotcobra03 Active Member

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    A/F codes?

    just learning from this ....code 33 is egr,44/94 are tab/tad,,,did he pull the wrong vacuum hose,,i was expecting 42/92 code to pop up? as to fuel pressure if 33psi was koeo and vacuum hook up than thats to low?(35-45)koer(27-37)33psi is good?
  11. hotcobra03

    hotcobra03 Active Member

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    code 41

    i didnt see what joel was saying to do with adding fuel ,that must be a trick of the trade,, call someone tell me if this is right for this car...H18 attempt to eliminate code 41 on engines with map sensor...disconnect and plug vacuum line to map ,,,,,apply 10-14 in. of vacuum to map sensor,,,start and run engine at 2000rpms for 2 minutes then allow engine to return to idle,rerun koer test,,,,is code 41 still present?NOTE DISREGARD OTHER CODES RECIEVED AT THIS TIME ...if no goto H1 check fuel pressure
  12. Haus

    Haus Member

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    so just find any flexible part on the return line?? is it an all metal line??

    im not sure what the feed line is and what line is the return. i dont want to crimp the feed line.
  13. Haus

    Haus Member

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    anyone??
  14. joel5.0

    joel5.0 New Member

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    Yep... the return line is the smallest from the the two lines at the fuel rail, or the line that goes connected to the port that comes out from underneath the FPR.

    [​IMG]

    If you crimp the feed line by mistake, the engine will simply shut down or not start. LUK
  15. Haus

    Haus Member

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    awesome. thanks for the picture. ill let you know what i find out when i do it. im gonna change the fuel filter tomorrow and ill see how the FP is after that


    but i wanted to try something today. i notice when i have the Vacuum line to the FPR the FP is about 32-33 PSI and when i have it disconnected i have a FP of about 41-42 PSI. so i ran the test with the Vacuum line disconnected so i have higher FP for the test but i know obviously i would have a vacuum leak

    but the only code i got is 91

    the 41 disappeared.

    dont know what this means but i found it interesting

    and another thing is when i let my car sit for about 40 mins i checked the pressure when the car has been sitting for that long and it was at about 10 psi. i dint think it was supposed to go down that far in a short amount of time


    Edit: i just had someone start the car while i check the FP with the vacuum line connected and then had them turn it off and it went down to about 10 psi with in 5 seconds
  16. joel5.0

    joel5.0 New Member

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    You should rerun the KOER with the FPR disconnected and line plugged. From the FP leakdown results, looks like either the FPR, FP to sender hose section inside the tank, or the FP check valve (= FP unit) might be at fault. As soon as you can find a section of the return line that can be pinched, it will also help ID if the FPR could be at fault........ prime system with return line pinched, if pressure drops that fast, the other alternatives are the ones to look into. LUK
  17. hotcobra03

    hotcobra03 Active Member

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    whats up?

    been reading story and find your back to step 1-2 ..guess going step by step you would have found this earlier,,,cant wait to see whats next,,hope you get this fixed soon
  18. Haus

    Haus Member

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    i dont know whats going on. this is weird

    i disconnected the battery for like 7 hours. pumped the break. Connected the battery. Disconnected the vacuum line from the FPR and plugged the line. started it up. drove for about 10 miles. got home. checked the codes and get System pass for KOEO and system pass for KOER.

    :shrug:
  19. fastfiftymike

    fastfiftymike New Member

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    Drive it around for an hour and see if the codes come back.

    Mike
  20. Haus

    Haus Member

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    yeah im gonna do that. tomorrow i got a job about 30 mins away so ill check it after i get back

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