Help me create the "Surging Idle Checklist"

Discussion in 'Fox 5.0 Mustang Tech' started by jrichker, Apr 10, 2005.

  1. pretty cool setup man...

    I think its important to state that even though liquid filled gauges work better under conditions where vibration is a factor. They shouldn't be used for monitoring your fuel pressure mine has cost me alot of money and stress all cause the gauge can't perform under the heat of the motor. I am going with a non liquid filled gauge or an electric one so I can be sure I am getting good readings. I taught my fuel pressure was the reason for my idle and stalling issues but its not. So I am still going through the list of things to check so far I changed the iac motor with an auto zone unit and seems alot better but not perfect yet next I plan to change the pcv and grommet cause its very loose and check for any more leaks...

  2. What is the ect and act sensors ? I would like to check them but have no clue what they are ?


    11.) Dirty or defective ECT and ACT sensors. Look for codes 21, 24, 51, and 54 when you dump the codes. The ACT sensor will get coated with gunk over time and may need to be cleaned.
    ACT & ECT test data:

    The ACT & ECT have the same thermistor, so the table values are the same

    Pin 7 on the computer - ECT signal in. at 176 degrees F it should be .80 volts

    Pin 25 on the computer - ACT signal in. at 50 degrees F it should be 3.5 volts. It is a good number if the ACT is mounted in the inlet airbox. If it is mounted in the lower intake manifold, the voltage readings will be lower because of the heat transfer. Here's the table :

    Voltages are measured across the two connector pins of the sensor with the sensor connected. Some safety pins used to probe the connector from the rear will be helpful
    50 degrees F = 3.52 v
    68 degrees F = 3.02 v
    86 degrees F = 2.62 v
    104 degrees F = 2.16 v
    122 degrees F = 1.72 v
    140 degrees F = 1.35 v
    158 degrees F = 1.04 v
    176 degrees F = .80 v
    194 degrees F = .61 v
    212 degrees F = .47 v
    230 degrees F = .36 v
    248 degrees F = .28 v

    Ohms measures at the computer with the computer disconnected, or at the sensor with the sensor disconnected.
    50 degrees F = 58.75 K ohms
    68 degrees F = 37.30 K ohms
    86 degrees F = 27.27 K ohms
    104 degrees F = 16.15 K ohms
    122 degrees F = 10.97 K ohms
    140 degrees F = 7.60 K ohms
    158 degrees F = 5.37 K ohms
    176 degrees F = 3.84 K ohms
    194 degrees F = 2.80 K ohms
    212 degrees F = 2.07 K ohms
    230 degrees F = 1.55 K ohms
    248 degrees F = 1.18 k ohms​
  3. ECT sensor = Engine Coolant Sensor. It is normally located in the heater feed tubing on the passenger side of the engine. Some cars without heater feed tubing may install this sensor directly into the lower intake manifold in place of the heater feed tubing. The computer uses this sensor to find out how hot the engine is and adjust ignition timing and air/fuel ratio.

    ACT = Air Charge Temperature. It is normally located in #5 intake runner on the driver's side of the car. It has two wires that connect it to the wiring harness. The temp gauge sender is nearby, but only has one wire and it is a push on connector. The ACT provides information to the computer about what temperature the incoming air is and uses that information to adjust ignition timing and air/fuel ratio. Sometimes the ACT may be relocated to the intake filter airbox because the manifold isn't drilled for it.
  4. plz remove, question answered
  5. Aside the inability to access the KOER self-test routine, code 67 could also create a surging idle condition. As a contribution to this thread, you may want to check the case I had the chance to document to prove it, at this "Proof that Code 67 causes idle control problems" I say.....Hope this helps.
  6. Pretty cool.

    Here is the question pertains to 5-speeds don't must people get that code because the clutch was not pushed in while they do the koeo test or do you get it because the clutch was out during test ?

    My car is a 5-speed I also get that code while I run that test, And I leave my clutch out not pushed in. Does that mean my switch is bad or does it mean that I just need to push in the clutch so I don't get that code while I run the koeo test ?

    Thanks for the video
  7. get the code because the gear switch at the T5 is faulty (open) when the shifter is in neutral. The setup in a EEC-IV/non-SN95 manual tranny uses 2 switches in a parallel circuit setup, one at the clutch pedal, one at the transmission......if either switch is closed, the system is id'ed "in neutral", if none is closed, the system is id'ed as "in-gear"......reason why you would have to keep the clutch pedal down to cause a system "in-neutral" condition....if the gear switch on the tranny is defective.......

  8. Oh ok that makes sense so how do I replace that switch where is it and do you have a part number ?

    I think I found it #E6ZZ-7A247-A Looks like only a ford dealer parts department might have it
  9. Rolling Idle Problem


    Only when the car is moving the idle will hang at around 1500 this is when the clutch is in or when I put the car in neutral and just watch the idle confused as I roll down a hill. I ran through the steps and set base idle and warm or cold she sits at about 800 when not moving. What would only effect rolling idle.

    But wait I am reading the vss sensor does this but it still doesn't seem normal.
  10. The VSS sensor will cause the engine RPM's to drop slowly when the car is rolling. The description of your problem sounds normal for a vehicle that is still moving.
  11. I can't help it, I have to say...this thread gives me such COLD CHILLS it hurts to the bone!!! If these new guys only knew.....:bang:
    This is a great thread JR! All I can say...from VAST do not be tempted to throw money into new parts to fix the problem. It's a sucker hole. Oh, it sounds like this solenoid, or that switch, or...believe me..IT'S NOT IT. Follow jrichker's checklist. It's so easy to start buying every little part in hopes it will cure your problem. Based on my very thorough experience, I wasted a ton of money on new parts that were not needed. Just wanted to share...
  12. I usually check out the vintage forums here but stumbled across this thread when I was having a surge issue with the 5.0 in my 87 Bronco. I thought I might share what I found to help someone else out.

    Recently my truck broke down wouldn't start when I went to the store one night and I ended up having the thing towed home. Turned out all the teeth had stripped off the cam gear of the timing set, fricken aluminum and plastic timing gears:mad: Anyway, I found a decent Cloyes double roller in the Summit catalog for like 30 bucks but it was n back order. There's an Autozone by my house so I went in there and and they could order me the same timing set for like 5 bucks cheaper and have it to me by the weekend, it was a wednesday. So I ordered that and also a radiator hose for a different car that I had been meaning to replace. The hose had to be ordered as well and came in the next day. When I picked up the hose I decided I should probably get a new cap and rotor, my old ones were pretty worn and all they had was Duralast so I bought that.

    So, Saturday morning I pick up my new timing chain get the thing all put back together, start it adjust the timing and park it on the street. Sunday I go to help a friend move and the truck runs ok until I get a block away and I get the idle surge at the first stop sign. I've had an intermittent surge/stall issue since I've had the truck so no big deal. I get on the freeway and it seems like it has a miss, but more like the ignition cuts out at a light throttle under load more than a miss really. When I get off the freeway about 20 miles later, the truck stalls then I get the worst surge I've ever experienced up to 1500 down to like 200 and on and on...

    After helping my friend the truck starts ok and idles ok till I put a load on it. I pulled over on my way home because it was way too annoying and thought I had a lose lead on the coil, I have an MSD and blade connectors instead of the stock harness/connector so I ended up switching the leads and it ran a bit better but would still surge and stall way more than ever. When I got home and got a flash light I found my EGR was stuck open and I managed to twist the negative cable on my battery with my bare hand. Go to tighten the cable and the bolt breaks, turns out it was really corroded near the head where it's hidden by the post. Clean out the EGR, replace the bolt and now I'm stoked cause I found the problem,but nope. I cleaned the throttle body my iac, set the voltage on my tps to .98 it was at like .87 or something did everything I could think of then found this thread. I went through the checklist and it seemed to work fine until I drove it, then mad surging and stalling.

    It really seemed like real bad missing when driving at really light throttle, though you couldn't hear a miss and at a stop it just had a real bad surge. Anyway after banging my head a couple of times into the core support :bang: I popped off the distributor cap and my new rotor looked like hell from only like 50 miles or so and the top of it that keeps in contact with the button on the cap is all bent inward. I bend that outwards and start the car and sure enough it runs a bit smoother. I put my old beat up cap back on and take it for a drive and almost no more surge and definitely no more stalling. I broke out the calipers and measured the two caps and the fricken duralast is almost an 1/8 inch shorter and the terminals in the cap were somewhere around 10 thousands or so closer to each other than on my motorcraft cap.

    I was happy that my Bronco ran now but pissed off that I had gotten a bad cap. I went to try to return it to Autozone but I didn't have the box anymore so they wouldn't take it back. Man, I've change a couple of hundred caps in my life but never ran across one that was indexed wrong especially not to a matching rotor... but I did end up returning all the other duralast crap, fuel filter and belt I hadn't put on yet. I still had a bit of a stumble and a slight very intermittent surge, only around a 100 rpm or so on my way there. I went to a Kragen that was up the street and they carried Borg Warner, so I bought a new cap and rotor, way nicer brass terminals and all, changed them out in the parking lot and noticed that I now had the leads on my coil switched backwards switched them back and the car runs better than it ever has since I've owned it, no more surge, no more stalling. It's smooth as silk at any rpm whether under load or not.

    Sorry for the long post. But if you do happen to change your cap and rotor especially while doing something else to the car so that it's not immediately noticeable as the cause double check that cause it will definitely cause a surge issue. I think the EEC is really good at covering up a miss. At least on my car although I thought it was missing under load I never really heard it, just kind of felt it and it still felt like the surging idle feels under light throttle. In my driveway I could only get a surge and never a miss and I never was able to get any code other than when I got my EGR suck open. If you have a cheap ass Duralast cap and rotor that might just be your problem...
  13. surge saga get's worse

    ok; so last year I went through a car wash and got a minor surge at idle in park....but it was minor and I never found any codes or other problems...

    now this year we flushed my heater core out (was clogged) and fixed a FPR the previous weekend; and now my surge issue is worse (more irratic sometimes and even in Drive and sometimes stalls after trying to adjust itself) then...other times it seems to be ok for a bit; but every time I drive the car now it'll give me issues.

    I ran the "key on" test and got these:
    31 -my EGR is's got no vacume line that works; so it's always closed now.
    81 -thermactor or IAC...btw my IAC is new last year and thermactor whole emissions is deleted
    85 -canister purge (deleted)
    95 -thermactor -deleted

    I ran the run test...but not sure I followed the directions and not sure if I can trust any of the results....

    first test: I think is suspect because my car wasn't warmed up completely; and I was using the wrong rpm proceedure.

    second test: I don't think I kept up the RPMs where they should have been so I don't trust the results. (I had to let off the throttle because my garage door needed to be opened up more to let out all the exahust.

    third test: performed exactly at 3000 rpm long enough; but now I realized I needed to perform a 2000 rpm test and restart the car for the v8' I guess all the tests are suspect now?

    below is the results of all three tests and how often each code came up:

    12 all -system cannot raise engine rmp above idle
    23 all -TPS...or at least it's not in the range it should be in for the "test proceedure" which I'm not sure I did correctly at 3000 rpm instead of 2000 rpm
    31 all -EGR vaccum (expected code; I know the EGR is not getting proper vaccum but it is closed)
    91 test 1 and 3 -EGO
    13 test 3 only -RPM out of spec
    26 test 3 only -MAF
    21 test 1 only -ACT: since it's test #1 I think it's an error the car not hot enough
    41 test 1 only -EGO sensor
    44 test 2 only -*I have my emissions "thermactor" stuff deleted
    94 test 2 only -*I have my emissions "thermactor" stuff deleted

    I guess I'll have to run the run test again tomorrow; because I'm sure if I didn't do the test correctly then the "specifications" will always show a defect code.

    also; if I had a fuel problem and it's fixed now....could it be possible I need to reset my idle if my fuel pressure is correct now and before it wasn't? Just trying to understand if changing/fixing my FPR and fuel leak issues now made my previous idle settings no longer good enough now that the fuel pressure is at 38-40 psi
  14. Nicoleb3x3, here are the answers for your codes.

    Code 21 – ECT sensor out of range. Broken or damaged wiring, bad ECT sensor.
    Note that that if the outside air temp is below 50 degrees F that the test for the
    ECT can be in error.

    The ECT sensor has absolutely nothing to do with the temperature gauge. They are
    different animals. The ECT sensor is normally located it the RH front of the engine in
    the water feed tubes for the heater.

    The ACT & ECT have the same thermistor, so the table values are the same

    ACT & ECT test data:

    Use Pin 46 on the computer for ground for both ECT & ACT to get most accurate

    Pin 7 on the computer - ECT signal in. at 176 degrees F it should be .80 volts

    Pin 25 on the computer - ACT signal in. at 50 degrees F it should be 3.5 volts. It is
    a good number if the ACT is mounted in the inlet airbox. If it is mounted in the lower
    intake manifold, the voltage readings will be lower because of the heat transfer.

    Voltages may be measured across the ECT/ACT by probing the connector from
    the rear. A pair of safety pins may be helpful in doing this. Use care in doing it
    so that you don't damage the wiring or connector.

    Here's the table :

    68 degrees F = 3.02 v
    86 degrees F = 2.62 v
    104 degrees F = 2.16 v
    122 degrees F = 1.72 v
    140 degrees F = 1.35 v
    158 degrees F = 1.04 v
    176 degrees F = .80 v
    194 degrees F = .61

    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.

    Ohms measures at the computer with the computer disconnected, or at the sensor
    with the sensor disconnected.
    50 degrees F = 58.75 K ohms
    68 degrees F = 37.30 K ohms
    86 degrees F = 27.27 K ohms
    104 degrees F = 16.15 K ohms
    122 degrees F = 10.97 K ohms
    140 degrees F = 7.60 K ohms
    158 degrees F = 5.37 K ohms
    176 degrees F = 3.84 K ohms
    194 degrees F = 2.80 K ohms

    Diagram courtesy of Tmoss & Stang&2birds


    See the following website for some help from Tmoss (diagram designer) & Stang&2Birds
    (website host) for help on 88-95 wiring

    Ignition switch wiring

    Fuel, alternator, A/C and ignition wiring

    Complete computer, actuator & sensor wiring diagram for 88-91 Mass Air Mustangs

    Vacuum diagram 89-93 Mustangs

    Code 23 - Throttle sensor out of range or throttle set too high - TPS needs to be reset to below 1.2 volts at idle. Keep in mind that when you turn the idle screw to set the idle speed, you change the TPS setting.

    Setting the TPS: you'll need a good Digital Voltmeter (DVM) to do the job. Set the TPS voltage at .5- 1.1 range. Because of the variables involved with the tolerances of both computer and DVM, I would shoot for somewhere between .6 and 1.0 volts. Unless you have a Fluke or other high grade DVM, the second digit past the decimal point on cheap DVM’s is probably fantasy. Since the computer zeros out the TPS voltage every time it powers up, playing with the settings isn't an effective aid to performance or driveablity. The main purpose of checking the TPS is to make sure it isn't way out of range and causing problems.

    The Orange/White wire is the VREF 5 volts from the computer. You use the Dark Green/Lt green wire (TPS signal) and the Black/White wire (TPS ground) to set the TPS. Use a pair of safety pins to probe the TPS connector from the rear of the connector. You may find it a little difficult to make a good connection, but keep trying. Put the safety pins in the Dark Green/Lt green wire and Black/White wire. Make sure the ignition switch is in the Run position but the engine isn't running.

    Here’s a TPS tip I got from NoGo50

    When you installed the sensor make sure you place it on the peg right and then tighten it down properly. Loosen the back screw a tiny bit so the sensor can pivot and loosen the front screw enough so you can move it just a little in very small increments. I wouldn’t try to adjust it using marks.

    (copied from MustangMax, Glendale AZ)

    A.) Always adjust the TPS and Idle with the engine at operating temp. Dive it around for a bit if you can and get it nice and warm.

    B.) When you probe the leads of the TPS, do not use an engine ground, put the ground probe into the lead of the TPS. You should be connecting both meter probes to the TPS and not one to the TPS and the other to ground.

    C.) Always reset the computer whenever you adjust the TPS or clean/change any sensors. I just pull the battery lead for 10 minutes.

    D.) The key is to adjust the TPS voltage and reset the computer whenever the idle screw is changed.

    If setting the TPS doesn’t fix the problem, then you may have wiring problems.
    With the power off, measure the resistance between the black/white wire and battery ground. You should see less than 1 ohm. Check the same black /white wire on the TPS and MAP sensor. More than 1 ohm there and the wire is probably broken in the harness between the engine and the computer. The 10 pin connectors pass the black/white wire back to the computer, and can cause problems.

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

    See for more wiring help & 10 pin connector diagrams

    Code 26 - Mass Air Flow out of range – MAF

    There are three parts in a MAF: the heater, the sensor element and the amplifier. The heater heats the MAF sensor element causing the resistance to increase. The amplifier buffers the MAF output signal and has a resistor that is laser trimmed to provide an output range compatible with the computer's load tables.

    The MAF element is secured by 2 screws & has 1 wiring connector. To clean the element, remove it from the MAF housing and spray it down with electronic parts cleaner or non-inflammable brake parts cleaner (same stuff in a bigger can and cheaper too).

    Look for 12 volts across pins A & B.

    The MAF output varies with RPM which causes the airflow to increase or decease. The increase of air across the MAF sensor element causes it to cool, allowing more voltage to pass and telling the computer to increase the fuel flow. A decrease in airflow causes the MAF sensor element to get warmer, decreasing the voltage and reducing the fuel flow. Measure the MAF output at pins C & D on the MAF connector (dark blue/orange and tan/light blue) or at pins 50 & 9 on the computer.

    At idle = approximately .6 volt
    20 MPH = approximately 1.10 volt
    40 MPH = approximately 1.70 volt
    60 MPH = approximately 2.10 volt

    Check the resistance of the MAF signal wiring. Pin D on the MAF and pin 50 on the computer (dark blue/orange wire) should be less than 2 ohms. Pin C on the MAF and pin 9 on the computer (tan/light blue wire) should be less than 2 ohms.

    There should be a minimum of 10K ohms between either pin C or D on the MAF and ground.

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

    Code 41 or 91 - O2 indicates system lean. Look for a vacuum leak or failing O2 sensor.

    Code 41 RH O2 Sensor
    Code 91 LH 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

    Testing the O2 sensors
    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.

    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.

    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.

    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.
    A secondary problem with only a code 41 is for cars with an intact smog pump and cats. If the tube
    on the back of the heads clogs up the driver’s side, all the air from the smog pump gets dumped
    into one side. This excess air upsets the O2 sensor calibration and can set a false code 41. The cure
    is to remove the crossover tube and thoroughly clean the insides to that there is no carbon blocking
    the free flow of air to both heads.
  15. 5.0 wants to die when I'm stopping after MAF conversion, HELP!

    I have a '88 LX 5.0 and it ran great until I put on the Mass Air conversion. Now, when I'm stopping, it wants to die. It seaches for idle and sometimes, if I don't feather the gas, it does die. The Mass Air we installed came off of a '90 GT and we tried cleaning the throttle body and the MAF sensor. STILL DOES IT. We hooked up the scanner and it gave us codes that had something to do with some canisters on the passenger side inner finder (inbetween the wheel and firewall) and we haven't messed with that yet. Could that have something to do with it? I'm just now becoming a Ford man after being a Chevy boy for 10 years (since I could drive). It's pretty annoying when it dies on me every 3rd or 4th stop. PLEASE HELP!
  16. Go back and read all of the very first two posts in this tech note.
    All the information on what to look for and how to fix the problem are in those two posts.

    Once you have worked your way through the checklist, then post your
    questions about whever specific area of the checklist you need help with.
  17. Listen, if it doesn't surge at idle, then it's just not a Mustang. That would take the fun out of it........
  18. hey guys,

    i'm not throwing codes but when the motor is cold it won't hold idle. i have to rev it up or it dies like an old carb'd car. then after warm it's cool.

    when i unplug the iac, the idle doesn't change so does that mean it's a bad iac? sorry if it sounds noob. i think the flu is affecting my mind. lol

  19. Go back and read the first page and the first two post on that page. All the tests and fixes are there.
    Once you have a specific question about one or more of the tests or fixes, make another post with
    your your results. I will try to help you resolve your problems.
  20. I did the 3g Alt. Conversion and it took care of about 98% of my idle problems... Im gonna do some electrical cleaning next. Awesome Thread!:SNSign: