Issues With The Mustang... :/

Discussion in 'Fox 5.0 Mustang Tech' started by antnvlz1294, Feb 14, 2014.


  1. antnvlz1294

    antnvlz1294 Member

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    Hey guys heres another fun thread.
    So as you all already know I currently own a 1988 mustang 5.0 lx. I bought the car back in november and I've had multiple issues. I currently have a misfiring issue so I was told to replace multiple things. I would get a misfiring/popping sound from my vehicle under a load and would feel like I am losing power until the car would catch up and speed up the misfiring ended. I replaced the fuel filter, sparkplugs (motorcraft gapped at .052), ignition wires (autolites), MSD Cap and rotor, MSD Ignition coil, Oil & filter change, Did a 3g alternator upgrade to a 130 amp alternator(kit bought from latemodelrestorations.com) with a bigger gauge wire that goes from the alternator to the ignition system, cleaned out the Iacv(looks brand new and had no carb build up in it at all so I believe that the previous owner knew about the issue), tested the TPS and it was at a .97 so it checked out good, I replaced the tfi ignition module(made no difference) so I was told I couldve been the pip sensor in the distributor. I just replaced the distributor about 2 weeks ago and when I did I made sure the #1 cylinder was top dead center and made sure the rotor was pointed toward the number 1 cylinder/sparkplug and installed the distributor. Then my neighbor(builds cars for atco raceway here in sj) used a timing light and set my timing to 12 degrees. After the new distributor (the brand is Tough One?) was installed I noticed that the car actually now bucks/jerks forward if i stay at a steady/constant speed. For example if I drive 25 mph for a while it'll buck/jerk forward a couple of times until I increase acceleration. Although this problem doesnt occur if I accelerate or am sitting at a light in neutral. After all of that work, the misfiring issue is still present, although it did seem to go away for a day or two after the distributor install. About a week ago I installed 6 new speakers and a new headunit correctly, and last night when I turned on my headlights, I noticed another problem now. The headlights were flickering and so was the lite up dashboard. The battery gauge on the dashboard itself was bouncing up and down as well(not giant bouncing but bouncing up and down as fast as the flickering). I've never had this issue before and it hasnt gone away since last night. It cant be the aftermarket headunit or speakers because this problem just began to happen and theyve been in for a week already. The negative and positive cables arent loose either so what could be the problem? The car still misfires/pops and bucks/ jerks forward at a constant speed and now I have this issue on top of it. I am really about to bash my head through a wall... I've only had the car almost 3 months now... and it didnt seem to have these issues the first few weeks i've had it... please help me...? :banghead:

    Thanks guys..
    #1
  2. 84Ttop

    84Ttop They make new pistons every day, so why worry? SN Certified Technician Mod Dude

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    First and foremost, have you dumped the codes? This is the first place to start before throwing more parts at it.

    Side note: where at in sj are you? I'm in Mullica Hill.
    #2
  3. antnvlz1294

    antnvlz1294 Member

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    That's the first thing I have done. The last time I checked the codes were before the distributor install two weeks ago which read system pass. I'll take my obd1 coder and see if I can grab any codes tomorrow. As for south jersey, I'm in mount laurel.
    #3
  4. A5literMan

    A5literMan Mustang Master

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    Def need to know about the codes first but for the misfire it might be a bad injector. The electrical problem sounds like a short in the system. Double check your 3G install and stereo installation.
    #4
  5. antnvlz1294

    antnvlz1294 Member

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    I triple check everything I do so its done right the first time. I think I might have a bad cell in my battery. I'm probably going to get my battery and system tested. but for now im going to let her run for a little and try to pull codes.
    #5
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  6. antnvlz1294

    antnvlz1294 Member

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    So i just went to advanced auto to get a system check. The battery test: Good Battery. Voltage: 13.02v, Measured: 654 CCA, Rated: 540 CCA, Temperature 59F "Battery Meets or Exceeds Required Standards". The Starter test: Cranking Normal: Voltage 10.52V, Amps: 0.0A, Time: 1.12S. The Charging System Test: Results: No Problems, No Loads: 14.99V, Loaded: 14.64V, Ripple: 88mV. Charging system output test normal. So is this a ground issue now?...
    #6
  7. 84Ttop

    84Ttop They make new pistons every day, so why worry? SN Certified Technician Mod Dude

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    Not a bad idea to start checking your grounds. The battery to the frame rail and the engine ground are the two most important. Also look for the grounds that are for the ecu and lighting circuits.
    @jrichker do you have a diagram for chassis grounds?
    #7
  8. jrichker

    jrichker StangNet's favorite TOOL SN Certified Technician Founding Member

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    First question to ask and answer:
    The SPOUT jumper is supposed to be removed when the timing is set using a timing light. Was it removed or left in place?



    Grounds

    Revised 28-Oct-2012 to add signal ground description & possible problems if it is bad

    Grounds are important to any electrical system, and especially to computer controlled engines. In an automobile, the ground is the return path for power to get back to the alternator and battery.

    1.) The main power ground is from engine block to battery: it is the power ground for the starter & alternator.


    2.) The secondary power ground is between the back of the intake manifold and the driver's side firewall. It is often missing or loose. It supplies ground for the alternator, A/C compressor clutch and other electrical accessories such as the gauges. The clue to a bad ground here is that the temp gauge goes up as you add electrical load such as heater, lights and A/C.

    Any car that has a 3G or high output current alternator needs a 4 gauge ground wire running from the block to the chassis ground where the battery pigtail ground connects. The 3G has a 130 amp capacity, so you wire the power side with 4 gauge wire. It stands to reason that the ground side handles just as much current, so it needs to be 4 gauge too.

    The picture shows the common ground point for the battery , computer, & extra 3G alternator ground wire as described above in paragraph 2. A screwdriver points to the bolt that is the common ground point.

    The battery common ground is a 10 gauge pigtail with the computer ground attached to it.
    Picture courtesy timewarped1972
    [​IMG]

    Correct negative battery ground cable.
    [​IMG]

    3.) The computer's main power ground (the one that comes from the battery ground wire) uses pins 40 & 60 for all the things it controls internally: it comes off the ground pigtail on the battery ground wire. Due to its proximity to the battery, it may become corroded by acid fumes from the battery.
    In 86-90 model cars, it is a black cylinder about 2 1/2" long by 1" diameter with a black/lt green wire.
    In 91-95 model cars it is a black cylinder about 2 1/2" long by 1" diameter with a black/white wire.
    You'll find it up next to the starter solenoid where the wire goes into the wiring harness.

    All the grounds listed in items 1,2 & 3 need to bolt to clean, shiny bare metal. A wire brush or some fine sandpaper is the best thing to use to clean the ground connections.


    4.) All the sensors have a common separate signal ground. This includes the TPS, ACT, EGR, BAP, & VSS sensors. This ground is inside the computer and connects pin 46 to pins 40 & 60, which are the main computer grounds. If this internal computer ground gets damaged, you won't be able to dump codes and the car will have idle/stall/ performance problems

    5.) The O2 sensor heaters have their own ground (HEGO ground) coming from the computer. This is different and separate from the O2 sensor ground. It is an orange wire with a ring terminal on it. It is located in the fuel injector wiring harness and comes out under the throttle body. It gets connected to a manifold or bolt on back of the cylinder head.

    6.) The TFI module has 2 grounds: one for the foil shield around the wires and another for the module itself. The TFI module ground terminates inside the computer.

    7.) The computer takes the shield ground for the TFI module and runs it from pin 20 to the chassis near the computer.


    See http://assets.fluke.com/appnotes/automotive/beatbook.pdf for help for help troubleshooting voltage drops across connections and components. Be sure to have the maximum load on a circuit when testing voltage drops across connections. As current across a defective or weak connection, increases so does the voltage drop. A circuit or connection may check out good with no load or minimal load, but show up bad under maximum load conditions. .

    Voltage drops should not exceed the following:
    200 mV Wire or cable
    300 mV Switch
    100 mV Ground
    0 mV to <50 mV Sensor Connections
    0.0V bolt together connections

    [​IMG]

    Extra grounds are like the reserve parachute for a sky diver. If the main one fails, there is always your reserve.

    The best plan is to have all the grounds meet at one central spot and connect together there. That eliminates any voltage drops from grounds connected at different places. A voltage drop between the computer ground and the alternator power ground will effectively reduce the voltage available to the computer by the amount of the drop.
    #8
  9. antnvlz1294

    antnvlz1294 Member

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    Just cleaned the grounds by the headlights (think theyre called the pigtails?), the ground between the battery and the ignition solenoid and the final ground that goes from the drivers side firewall to the engine. Scraped it with sandpaper (didnt have a wire brush) bare silver metal; no paint.
    #9
  10. antnvlz1294

    antnvlz1294 Member

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    The spout connector was out when the timing was set. Was also plugged back in afterward. As for the ground that Is above in the picture (the on shown with the screw driver by the battery/ ignition solenoid), It is the exact same one in the picture. It isnt a 4 gauge ground wire. Is that the issues, even though this problem just popped up?.. As for pulling codes, Just used my actron obd1 code scanner. On the KOEO test I got system pass. On KOER test however, I got code 41. Code 41: Exhaust Gas Oxygen (EGO) sensor: Voltage Signal always "Lean" (low value) - does not switch. This wouldnt have anything to do with my whole bucking/ jerking forward, dashboard and head light flickering and battery gauge jumping issue would it?...
    #10
  11. jrichker

    jrichker StangNet's favorite TOOL SN Certified Technician Founding Member

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    You probably have several different problems instead of just one problem.

    The picture shows the proper place for the 10 gauge computer ground and for any auxiliary grounds. The 86-93 cars with a 3G alternator should have a 4 gauge ground from the engine block to the ground shown in the picture.


    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.
    #11
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  12. antnvlz1294

    antnvlz1294 Member

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    I have a 4 gauge wire with two ends that are circular for a bolt to go through in order to hold it into whatever I want(both ends look like my attachment to this post. where should I put it? Should I put it underneath where the negative battery cable connects to the engine to underneath the ground connection in the picture shown?

    Attached Files:

    #12
  13. Grabbin' Asphalt

    Grabbin' Asphalt Mustang Master

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    I have 2 for back up, 4 gauge wire to the firewall (replaced the strap) and one that connectes to the fender, like in the pic by the battery, its connected to the block where the neg from the battery goes to.
    #13
  14. jrichker

    jrichker StangNet's favorite TOOL SN Certified Technician Founding Member

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    Take Grabbin' Asphalt's advice and run with it...
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  15. antnvlz1294

    antnvlz1294 Member

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    Ok
    Okay I'll be taking my 1st 4 gage wire and be attaching it underneath the negative battery cable mount on the engine block and underneath the original ground. I'll then buy another one. Thanks guys
    #15
  16. Grabbin' Asphalt

    Grabbin' Asphalt Mustang Master

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    Having all your grounds covered with insurance can help narrow down any other problems that ever pop up, also you know you're covered in that dept and can cross it off first.
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  17. antnvlz1294

    antnvlz1294 Member

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    By "insurance" you mean grounds? lol and will do thanks
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  18. Grabbin' Asphalt

    Grabbin' Asphalt Mustang Master

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    Yes I do because with a 3g upgrade, one is to equally upgrade the ground wire with the 4 gauge power wire, not doing so is putting a fire hazard into your car because it does not have an equal point of return. But adding the extra 4g wire (where the strap is, clean connection etc) insures that, along with proper dash gauge readings. When I say proper, meaning the best the stock gauges can offer. Then just go down the list @jrichker has, his lists are the best in the business :nice:
    Last edited: Feb 15, 2014
    #18
  19. antnvlz1294

    antnvlz1294 Member

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    Well I went to put a 4 gauge wire from where the negative battery cable mounts to on the engine to the ground next to the battery, and It didnt reach so I took it back but they didnt have a longer wire. Instead I bought a 4 gauge negative battery cable(same as the original) the only bad thing about it is that its 78 inches long which is too long causing me to ziptie and electrical tape a bunch of it together.. anyway I put that on and the car started right up and the battery gauge stopped bouncing and the dash and headlights didnt flicker the rest of the day. Today however I started my car and those issues are back... what do I do now? I had everything tested under load and posted the results above^ so its not the alternator... Maybe the battery then? do I need a bigger and better battery? I have a cheaper one its "pro start"...
    #19
  20. Grabbin' Asphalt

    Grabbin' Asphalt Mustang Master

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    Mine too is black neg cable from the auto store, mine is a little longer and zip tied some as well, maybe not as long as yours cause I measured what I truly needed. I did the same small length black neg cable for the firewall to rear of intake strap replacement. Many of your gauges get the ground from THIS spot so do it as well.
    #20

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