Hesitation/bogging Down..

Discussion in 'Fox 5.0 Mustang Tech' started by sleepysheila88, Oct 15, 2013.

  1. Hi everyone I'm hoping you can help with solving this mystery..

    Now a little back story..

    2 years ago i had my 5.0 rebuilt by a local builder for my 88 speed density mustang. He bored the engine over and added hyereutic pistons and increased the compression a little. At the time i also added cobra intake and new 19lb accel injectors (busted one of the stock ones taking it out of the lower intake). After installing the engine and going through the break in period i noticed it just didn't seem to have what it used too. Without any load the engine idles and rev's amazing. Under load its a different story. Basically if you pull away and accelerate lightly the engine runs up through the revs great. If you launch hard it pulls like crazy till around 2800- 3000 rpms and then she sort of bogs out... keep pushing it and she will eventually walk her way through it. Since then i have been chasing this issue and have not been able to solve it.

    List of mods at the time of the rebuild..
    Cobra Intake
    Adjustable fpr (set at 39)
    190 lph fuel pump
    Fuel filter
    Electric Fan
    Underdrive pulleys
    Ford Racing wire
    Autolite 25 plugs (gapped at .052)
    SS Shorty Headers
    Stock Cam (trying to keep the computer happy)

    List of mods since and parts replaced (trying to find/fix the issue)
    70mm throttle body
    AFR 1472 heads (suspected the stock e7 head's springs were weak, good excuse to upgrade anyway [​IMG] )
    1.7 rr
    MSD Blaster TFI Coil
    MSD Dizzy
    Ford racing wires (3rd set)
    Autolite 3924 (gapped at .040)
    FPR has been set to 42
    New MAP sensor
    New EGR
    New EGR Solenoid
    New TAB and TAD solenoids
    New TPS
    New ACT

    I have run the codes the a hundred times over the last 2 years and up until 2 weeks ago it has always been 11. The last little bit its now showing codes 94 and 44. I have tested the vacuum diverters and everything seems to be working.

    I had a local ford mechanic do the head install and set up the tune. He played with the timing for hrs adjusting it in increments. The last time he had it advance to 24. He stated at the time that it was acting like it wanted more but he was not willing to go there.. The car now runs great except for the hesitation problem.

    I'm running out of ideas any suggestions??

    Sorry for the long post..
  2. The recommended timing is 12-14 degrees initial timing with the SPOUT out. Don't go more that 16 degrees initial timing with the stock computer because you will have more than 38 degrees total. Past 38 degrees, the engine is working against the spark advance and not with it.

    You will need a timing light to properly set the ignition timing. If you don't have one or can't borrow a timing light, don't bother trying to set the timing. You'll never get it right without one.

    Setting the timing:
    Paint the mark on the harmonic balancer with paint -choose 10 degrees BTC or 14 degrees BTC or something else if you have NO2 or other power adder. I try to paint TDC red, 10 degrees BTC white and 14 degrees BTC blue.

    10 degrees BTC is towards the drivers side marks.

    Note: setting the timing beyond the 10 degree mark will give you a little more low speed acceleration. BUT you will need to run 93 octane to avoid pinging and engine damage. Pinging is very hard to hear at full throttle, so it could be present and you would not hear it.

    Simplified diagram of what it looks like. Not all the marks are shown for ease of viewing.

    ATC ' ' ' ' ' ' ' ' ' '!' ' ' ' ' ' ' ' ' ' BTC
    ---------------- > Direction of Rotation as viewed standing in front of the engine.

    The ' is 2 degrees.
    The ! is TDC
    The ' is 10 degrees BTC
    Set the timing 5 marks BTC. Or if you prefer, 5 marks towards the driver's side to get 10 degrees.

    To get 14 degrees, set it 7 marks BTC. Or if you prefer, 7 marks towards the driver's side to get 14 degrees.

    The paint marks you make are your friends if you do it correctly. They are much easier to see that the marks machined into the harmonic balancer hub.

    At this point hook up all the wires, get out the timing light. Connect timing light up to battery & #1 spark plug. Then start the engine.

    Remove the SPOUT connector (do a search if you want a picture of the SPOUT connector) It is the 2 pin rectangular plug on the distributor wiring harness. Only the EFI Mustang engines have a SPOUT. If yours is not EFI, check for a SPOUT: if you don’t find one, skip any instructions regarding the SPOUT
    Warning: there are only two places the SPOUT should be when you time the engine. The first place is in your pocket while you are setting the timing and the second is back in the harness when you finish. The little bugger is too easy to lose and too hard to find a replacement.

    Start engine, loosen distributor hold down with a 1/2" universal socket. Shine the timing light on the marks and turn the distributor until the mark lines up with the edge of the timing pointer. Tighten down the distributor hold down bolt, Replace the SPOUT connector and you are done.

    The HO firing order is 1-3-7-2-6-5-4-8.
    Non HO firing order is 1-5-4-2-6-3-7-8


    Codes 44 & 94 - AIR system inoperative - Air Injection. Check vacuum lines for leaks, & cracks. Check for a clogged air crossover tube, where one or both sides of the tube clog with carbon.


    Revised 21 Sep 2012 to correct the description of the process that sets the code and include Thermactor Air System diagram.

    If you have a catalytic converter H pipe, you need to fix these codes. If you don't, then don't worry about them.

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

    The TAD solenoid/TAD diverter valve directs smog pump output to either the crossover tube attached to the cylinder heads or to the catalytic converters.

    The O2 sensors are placed before the catalytic converters, so they do not see the extra O2 when the smog pump's output is directed to the converters or the input just before the converter.

    The 44/94 code uses the O2 sensors to detect a shift in the O2 level in the exhaust. The smog pump provides extra air to the exhaust which raises the O2 level in the exhaust when the smog pump output is directed through the crossover tube.

    When there is an absence of increase in the O2 levels when the TAD solenoid/TAD diverter valve directs air through the crossover tube, it detects the lower O2 level and sets the code.

    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.

    Testing the system:
    Note that the engine must be running to do the tests unless stated otherwise. For safety’s sake, do test preparation like loosening clamps, disconnecting hoses and connecting things to a vacuum source with the engine off.

    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 following computer tests are done with the engine not running.
    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. Turning the ignition to Run 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.

    The following computer tests are done with the engine running.
    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 with the engine running. 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.

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



    If you have a catalytic converter H pipe, you need to fix these codes. If you don't, then don't worry about them
  3. Wow thanks for the information! I've been working alot of overtime this week so not alot of time to play with the old girl. I will do some more testing and let you know how i make out.

    Thanks again for the reply :)

  4. why did you change the fuel pressure from 39?
  5. The mechanic who installed the heads said it seemed to run better with the pressure bumped. I personally didn't notice a whole lot with the change.

    That being said i think i finally found the culprit today. I switched out the o2 sensors which were the only sensor i hadn't changed. The computer never showed that there was an issue with them but i suspect they had just gotten lazy. Installed 2 new ones and the car is back to normal. Doesn't seem to hesitate anymore and the idle seems alot more smooth. I still don't think she is 100% yet but i suspect the remaining issues are definately timing related.

    Thank you everyone who replied :)

    Now for this winter projects lol