Help me create the "Surging Idle Checklist"

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

  1. Just wanted to add, I purchased the scanner from the link in the first post and they sent me part # 3149 which is the extension cable and is the same price. Called them and told them what happened, they have a new package in transit. Couldn't ask for better customer service

    "Or for a nicer scanner see EQUUS DIGITAL FORD CODE READER (3145) – It has a 3 digit LCD display so that you don’t have to count flashes or beeps.. Cost is $30."
  2. Just thought I would add:

    When troubleshooting the O2 sensor ground you may need to run a ground strap from your h-pipe to the body to get a good ground. The O2 sensors ground through the h-pipe then through the headers to the engine.

    My stock headers and h-pipe wouldn't give my O2 sensors a good ground path resulting in codes 41 and 91. I tried almost everything I could think of to fix the codes. As a last resort, I installed the ground strap from a bolt on the h-pipe to the body and the codes went away. Its been about 2 years and I haven't seen a CE light.
  3. Good idea, most people wouldn't think of it
  4. The standard O2 sensor ground is an orange wire that comes out of the engine mounted fuel injector wiring harness. Ground it to either the back of the cylinder head or one of the intake manifold bolts. The 4 cylinder O2 sensors are 4 wire and will fit in a 5.0, but they do not use the same grounding method. The 4 cylinder O2 sensor harness is also different from the 5.0 harness.

    An extra ground is OK, but the stock one should work just fine. Make sure the secondary power ground from the intake manifold to the body isn't loose, damaged or missing. it provides the ground for the alternator, gauges and A/C compressor clutch.
  5. Great thread. I'm new over here, and don't remember if I saw a link from another Mustang forum or not, but great thread.

    I have been fighting with some idle and throttle issues for some time now. (as alot of us have) Recently, it started when I went to a new tuner and he reset my tune. At that time, I had also made some fuel system changes, but the idle issues didn't really happen until the tune was reset.

    We were trying to fix a long-time fuel lean condition above 5500 rpm, and ended up fixing it by making a few fuel system changes: replaced the GSS307/T-Rex combo with a GSS340 (ditched the T-Rex), swapped out the 42's with 60's, and added a Kenne Bell Boost-a-Pump.

    I had an old Autologic chip, which doesn't have alot of tuning parameters. So, I upgraded to a newer chip, and my tuner spent alot of time trying to get the issues resolved. It had a high idle, was hanging way up during shifts, surged a bit, and was very slow to come down. But, if I put the clutch in, then it would come down. Very frustrating especially considering that we had finally figured out my top end lean condition.

    Here's what I did:
    Fixed my grounds - I had relocated my battery to the trunk, and the gound was connected back there to the chassis. I had also hid my wires, had the computer ground connected to a spot under the fender liner, and the screw was loose. ^%$#@!~ I ran a new ground wire from the battery to the tranny, and also extended the computer ground to that same spot on the tranny so it is in contact with a ground wire coming directly from the battery.

    Did the base idle reset - I have always experienced that when I did the base idle reset (Ford Mustang Base Idle Reset), as soon as I reconnected the IAC, the idle would go up a few hundred rpm. And, since my idle was high lately, even after doing it, I decided to set it very low with the IAC disconnected. I set it to about 500, and then used the idle bypass plate to raise it a little bit so that it would keep an idle. When I reconnected the IAC, it went up, and is now around 850-900 or so. The custom cam doesn't seem to like stock idle rpm, so that is about as low as I can go.

    Reset the tps - which is, of course, required after resetting the idle. I was only able to get it to about .93 volts without elongating the holes, but after tens of hours of research on this in the past should be fine.

    Cleaned the 10-pin connectors - Ford Fuel Injection 10-pin Connector Fix Nothing to add here

    Used the idle bypass plate - I know that alot of people think this is a band aid, and it probably is. But, I spent ALOT of time tweaking the allen screw with this after the above things, and have it idleing very nicely now! It is actually a pleasure to drive, doesn't die, the idle comes down nicely when driving, and it idles great at a stoplight. I think this is what really helped, as it still had alot of surging and would die even after the other things listed above.

    The car is a joy to drive again. I haven't been driving it much because it was annoying to drive with the hanging idle.

    Sorry for the book.
  6. Do an advanced search using jrichker as the user name and the word mounted. You will find two tech notes on rear mounted battery that will fix a lot of the problems associated with this modification.
  7. Thanks, good info.

    One question. Is it necessary to use the alternator ground specifically, as opposed to how I did it by connecting it to a 1/O cable directly from the battery ground?
  8. The idea is taht since most of the electrical items in the car use the body as a ground point that the alternator grounds to the body. That way it does not depend on another ground wire to provide a return path for the electrical power.

    One 4 gauge wire from the block where you connected the battery ground wire to
    the chassis ground where the battery was mounted up front. Use a 5/16” bolt
    and bolt down the 4 gauge engine to chassis ground, make sure that it the metal
    around the bolt is clean & shiny. This is the alternator power ground.

  9. I was trying to track down a drivability issue that included an idle problem and figured the solution might help some one else.

    I tried a bunch of other things with no success. I decided to switch out the Idle air control solenoid with a spare one I had.
    I took them both apart to make sure they both worked and where clean, and low and behold, the one I was using on the car was missing the rubber oring that keeps unmetered air from entering the IAC.

    You can see the Oring on the right
    Here you can see the oring on the solenoid.

    I had bought a used Ford Motorsport 65mm throttlebody off eBay and either it didn't have the oring in it when I got it, Or I took it off when I was cleaning it and forgot to put it back on.
    Basically a 2 cent oring was driving me nuts.
    Car idles fine now.
  10. Thats honestly something Ive never thought about.

    Thanks, Now I can say," hey man, check your IAC valve O-ring"........LOL
  11. I think it would help if you can describe "driveablily issues"
  12. I didnt want to clutter up the "surging idle checklist" thread with stuff that wasnt related.

    You can see my tortured path here.

    and here

    I had a bunch off different stuff going on, including a Bad o2 sensor harness, a vacumn line leaking, as well as that oring missing.
    I assumed just one thing was wrong, it turned out to be a combonation of things.

    My Car is still not 100%.
    The car has never run right since I got her back in 1995.
    I just learned to live with some things over the years. Not anymore
    The quest for perfection continues.
    I will continue to update the threads I started with any solutions I find.
    Thankyou Stangnet for all the usefull info.
  13. had to replace throttle body gasket, EGR gasket, upper/lower intake gaskets, and almost every vacuum hose/line and re do the timing twice to get my idle almost right. and cleaned everything while i had it out.. all i can say is be thorough when replacing vacuum lines. might as well do them all at once. it'll save you from guessing which ones to replace. plus, they'll all need to be done eventually... that's my two cents. idk if this has exactly been said cuz i didnt read all fourteen pgs of posts..
  14. I had an idle surge of about 200 - 300 RPM on my /90 5.0. I corrected it by replacing the screen under the PCV valve. It probably was the original screen and had about 170,00 miles on it. I think they should be cleaned or replaced every 10,000 miles.
  15. Consistent cold first start only idle problem 86GT AOD

    NO CODES. Runs great when warm after initial 5 minutes of running.I read alot of the surging idle posts but didn't resolve issue for me.

    86GT AOD bone stock with 119k original motor. Many new FORD parts for reliability concerns only.

    First start of day in FL. Meaning never really "cold". Only happens on first start of the day. Fires right off first hit of key.

    Idles up properly 2k rpm then lowers back down to about 750 and stays there for 3 minutes. Never a problem starting. Then starts to drop to 250 and back up to 600 (surge) for next two more minutes (if AC is left on will sometimes stall). Then idles fine @ 750rpm in Park after that 2 minutes is up. Runs fast like a new car. Idles smooth at 550 in drive. If AC stalls car (during 2 minute period) and I restart it with AC load off it is fine. It is ONLY the first start of the day it has always done this for last 2 years we have owned the car.

    Obviously if I start driving the car before the 3 minutes is up there is no issue.

    It's only when I wait for my wife and let it warm up or want to do some work on the car requiring alot of idling that this is an issue.

    Car has been thoroughly gone over. New Ignition module, distributor, wires, plugs, IAC, PVC and screen replaced, base timing set, fuel pump and filter, cleaned injectors. Pulls hard thru all shift points pedal to floor. Runs great.

    Never happens again during the day once the car has been driven. Even if it sits for hours. Mechanics can't find it (with no codes) as they only get one shot in the morning for 2 minutes so they throw up their hands.

    **Yes I can easily live with this but would love to fix it after all this time. Especially since it is my wife's car and she thinks cars should virtually drive themselves.
  16. Time to get the DVM out and check the TPS before the first start. Continue to monitor it as the engine warms up. Be sure to leave the A/C off, since this may cause the engine to stall out and disrupt your monitoring efforts.

    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 drivability. The main purpose of checking the TPS is to make sure it isn't way out of range and causing problems.

    Wire colors & functions:
    Orange/white = 5 volt VREF from the computer
    Dark Green/lt green = TPS output to computer
    Black/white = Signal ground from computer

    TPS troubleshooting steps:
    1.) Use the Orange/white & Black white wires to verify the TPS has the correct 5 volts source from the computer.
    2.) Use the Dark Green/lt green & Black/white wires to set the TPS base voltage. Try this... All you need is less than 1.0 volt at idle and more than 4.25 at Wide Open Throttle (WOT). You'll need a voltmeter with a 1 or 3 volt low scale to do the job.

    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.

    The TPS is a variable resistor, must like the volume control knob on a cheap radio. We have all heard them crackle and pop when the volume is adjusted. The TPS sensor has the same problem: wear on the resistor element makes places that create electrical noise. This electrical noise confuses the computer, because it expects to see a smooth increase or decrease as the throttle is opened or closed.

    TPS testing: most of the time a failed TPS will set code 23 or 63, but not always. Use either an analog meter or a DVM with an analog bar graph and connect the leads as instructed above. Turn the ignition switch to the Run position, but do not start the engine. Note the voltage with the throttle closed. Slowly open the throttle and watch the voltage increase smoothly, slowly close the throttle and watch the voltage decrease smoothly. If the voltage jumps around and isn’t smooth, the TPS has some worn places in the resistor element. When the throttle is closed, make sure that the voltage is the same as what it was when you started. If it varies more than 10%, the TPS is suspect of being worn in the idle range of its travel.
  17. Jrichker is KING but you all ready knew that!!

    I shopped around for a couple days with discounts and free shipping and picked up a new TPS. Original was less than perfect per instuctions and of unknown age/manufacture.

    #1 Installed it and erased ECU memory with 10 minute battery disconnect and it totally changed the time for idle drop down and was much better BUT now idle would surge errattically in 2 minutes instead of three BUT would normally not stall anymore!! GOOD ADVICE.

    #2 Got a great price with free delivery on IAC valve in less than a week so decided to replace the year old one "just because it was cheap". Installed it and instantly the car ran much better in all throttle positions with NO surge or stalling but idle was remaining at 750 all the time. SO I decided that someone had messed with base idle screw. Lowered 1/8 turn with engine hot and running. Erased ECU memory again. Restarted engine. AWESOME!! Never has run this well. No stumble at any speed or throttle position!! (Used to have a slight hesitation at redline full throttle prior to automatic shift but not anymore.)

    #3 The big test. Overnite cold FL engine start at 60F. Started perfectly as usual only went to 1800rpm for short time and quickly/smoothly came down to 1100ish for about one minute. After two minutes was idling perfectly at about 700-750rpm on tach. At EVIL 3rd minute it wobbled for a few seconds but never went below 650rpm and continued to idle PERFECTLY!! Turn on AC and idle rose for the first time ever about 100rpm!!

  18. Thought I'd share one. After going through the motions on the surging idle checklist (replace cap and rotor, plugs, wires, fuel filter and ignition coil) and checking vacuum and fuel pressure my buddy and I finally decided to pull the valve covers where we found this.



    It is an exhaust valve. So it would run, just not very well. Now that its repaired it runs great once its warmed up, but its still has rough idle when cold.
  19. fixing the surging idle problem


    After cleaning the EGR valve and replacing the ignition control module I have determined that was the main cause of my surging idle.

    The after effects of changing the ICM is that I didn't put a timing light on. Once I did that I realized that my engine was out of time and I adjusted it accordingly.

    This made the engine run much much better. I took it for a test run and I didn't experience any surging idle, but I did get one stall coming into a stop light.

    I decided to do the routine maintenance on it and changed the oil and changed the fuel filter since that was mentioned on this list of items to check for. Added to that, I don't know when the last time it was replaced.

    Once I did all of that I took it for a test run, no surging idle, no stalls.

    The only thing I did experience is that when I came up to a couple stop lights, the idle would drop to about 250 and then speed up and level out around 650. It didn't stall or continue to surge. I am thinking this is normal, but please feel free to chime in if you don't agree.

    So I think to sum it all up the culprit in my case was 3 fold...

    1. Plugged EGR - got a code 33
    2. Bad ICM - got a code 18
    3. Fuel Filter

    Thanks everyone for your help. I am no longer afraid to take the mustang out for a drive. It stranded me once.

    Bonus: I found out my starter was on its way out, so I changed that and the solenoid. It will still crank a little slower than I would like when it is warm, but I think a bigger battery would fix that.

    Thanks again,

  20. I have an 89 lx 5.0 5spd that is bone stock save for exhaust, gears, and a clutch. My issue is that the car will start right up when the motor is cold (Outside air temp currently 95 to 100 degrees in the afternoon), but then go from 1100 rpms for 15 seconds then 1000 rpms for a couple of seconds, then to 800 rpms for a couple of seconds...until it bucks and stalls. I have replaced all of the following sensors:


    I have spark and also fuel, also have checked for vac leaks and have come up with nothing. The issue didn't really do it when the outside air temp was cool but I think that it is because it has just been getting worse as the weather gets warmer. The motor won't even stay running long enough to do a KOER test after it kicks the idle down. ANY help would be awesome as I am about to pull my hair out of my head. Also post below if you need some more information and I will gladly get it for you.