Help me create the "Surging Idle Checklist"

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

  1. I have a surging idle on cold start only (500-1500rpm). As soon as it begins to warm up, my idle is perfect (See idle vid in signature). Am I correct to say that the only things to blame could be the IAC or the timing. I already have the idle adjustment plate and a new alternator.
    What are some other things that could be wrong on a cold start and not on a warm engine?
    BTW Car idles fine around 600-700 RPM with the IAC disconnected.
  2. 1. My idle is set to about 850-900 rpms, and when im driving only sometimes for some reason after about 5 minutes or so, i'll stop and let my foot off the clutch and the rpm will stay at 2,000 rpm and not go down unless i turn the car off and then on again. This is happening too much lately. Any ideas?

    2. This is a different problem but, also, for as long as i can remember when im driving and i let off the gas and take my foot off the clutch and drop it in nuetral or whatever the car's rpm stays up higher then idle then when i come to a complete stop, after a second then it will drop to regular idle.

    any ideas?

    thanks in advance

    also when i disconnected the IAC connector the idle did'nt change at all?
    is'nt it suppose to?

  3. Read the very first post in this tech note: it has all the answers. Once you have completely read it, print it off and read it again. Then take a highlighter and mark the sections that pertain to your problem. The answer is in there.
  4. i got it down to 800rpm but when i turn it dies????

    do 02 sens have to do with idle
  5. Once the engine warms up enough for the computer to go into closed loop, the O2 sensors have a great effect on idle.
    Go back to the first post and read on how to dump codes. You may have some codes that need attention.
  6. Here's another checklist success story: I went throught the list step by step, and it ended up being the salt and pepper shakers. My surging problem had been bugging me for about a year and a half. The cause ended up being the Ford recall jumper harneses. If your car has them, pitch them in the trash. Here's a good link for more info (I don't think it's been posted on this thread):
    I'd suggest following it just for preventative maintenance.
  7. I have an E303 cam, and the idle has always been a little rough. Every once in a while if you could tell you have to give it gas or it's going to stall... really only for a second when the car first started and then it was fine from then on!

    So recently the car has been doing fine, but when it warms up, if I go into neutral, it would die down to about 500 and try about 3 or 4 times to go up to about 1500 and die. It goes VROOM.... VROOM.... VROOM.... *clunk* or something of the sort.

    One time I was coming home and I shifted out of forth gear and went to neutral just to coast for about 1/4 mile downhill to my turn. The second I put it in neutral and let off the clutch it did the above mentioned... and finallly stalled at about 20 MPH.

    Soooooo.... I cleaned the TB, and I also cleaned the idle air which seemed to REALLY help steady the car at about 800-900RPM, and it was great. However, the car died once when I first started it, as the E303 cam always has.

    My problem with the driving around and stalling the second I shift into neutral is finally gone for the most part.

    Any way to tackle this thing so it doesn't stall at all?
  8. Sorry double post.
  9. The first post has all the fixes, and steps through the how to find and fix you idle problems without spending a lot of time and money. I continue to update it as more people post fixes or ask questions.
  10. So my cold idle surging continues. The IAC and timing are not a problem. If anyone has any other ideas that could relate to cold idle only, let me know. For now I will keep going through the general idle problems.
    Can a vaccum leak be out of question if my car idles good when warm?
  11. bad azz dragon
  12. Yes. Cold engines enrichen the fuel mixture, making them a little less sensitive to mixture variations. When the engine warms up & goes into closed loop, there is much tighter control over air/fuel ratio.
  13. Im not exactly sure if anyone has wrote this in this thread Before but i have beeen a victum of this surging Idle so i jumped the DLC and did the flash test KOEO test and got code 63 TPS signal open so i took off my TPS which was new from autozone and tested it it should have 5000 Ohms when probling i think sig rtn and TP signal and when probingsig return and Vref you should have 0-5000 Ohms varing with tps location anywho long story short i hooked up a tps we found in the shop and tested it first put it on the car and surging idle GONE! New parts dont mean good im dealing with another problem code 94. blahhhh!
  14. Need help hear my car has been running crappy for a while idle and stalling issues
    just got a pmas 75mm mass air from anderson and its been ok for 1 week today the check engine light came on and I ran codes and got


    I saw 66 mass air voltage to low how do I fix that ? my mass air is new and its pluged in wires look fine

    And 67 I think because I didn't have my clutch pushed in
  15. Code 66 MAF below minimum test voltage.
    Insufficient or no voltage from MAF. Dirty MAF element, bad MAF, bad MAF wiring, missing power to MAF. Check for missing +12 volts on this circuit. Check the two links for a wiring diagram to help you find the red wire for computer power relay switched +12 volts. Check for 12 volts between the red and black wires on the MAF heater (usually pins A & B). while the connector is plugged into the MAF. This may require the use of a couple of safety pins to probe the MAF connector from the back side of it.

    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).

    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. Be sure to measure the sensor output by measuring across the pins and not between the pins and ground.

    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 wiring connector and ground. Make your measurement with the MAF disconnected from the wiring harness.

    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 pump, alternator, ignition & A/C wiring

    Computer,. actuator & sensor wiring

    Fuse panel layout

    Vacuum routing
  16. Code 67 - clutch not depressed (5 speed) or car not in neutral or park (auto) or A/C in On position when codes where dumped. Possible neutral safety switch or wiring problem. This code may prevent you from running the Key On Engine On tests. You can generally ignore this code, since it has no effect on engine performance.

    The computer wants to make sure the A/C is off due to the added load on the engine for the engine running tests. It also checks to see that the transmission is in Neutral and the clutch depressed (T5, T56, Tremec 3550 & TKO)). This prevents the car from being driven while the computer is in test mode. Key On Engine Running test mode takes the throttle control away from the driver for several tests. This could prove hazardous if the computer was jumpered into test mode and then driven.

    The NSS code 67 can be bypassed for testing. You will need to temporarily ground computer pin 30 to the chassis.
  17. Thanks I will check that later and go through the list of things to check that are on the first page to get my car to start, idle, and drive good.

    I had no clue so many other fox body's out there had the same exact issue this forum is a great source of help I have already spent over 2k believe it or not at performance shops in labor and parts with no success I look forward to trying everything to correct my issues.
  18. Can fuel pressure drops cause idle issues and stalling ?

    I have a liquid filled bbk fpg on my fuel rail and if I set the psi to say 39 with vac line off it will creep down to say 35 34 when car gets hot.

    I have a bbk fpr and its new as well as a new 190 pump replaced both same problem

    Can it be the gauge I heard liquid filled gauges are not good at all because when they get hot they become unreliable

    read it for yourself line 2
  19. If the liquid inside the gauge gets hot, the increase in pressure inside the gauge case would affect the readings. As you know as a liquid gets hot, it expands. An expanding liquid inside a closed container increases in pressure, just like a car's radiator.

    Here's a cheap and easy substitute for a gauge on a fuel rail...

    Fuel pressure gauge adapter fittings: AN 4 to 1/16” pipe 1/16” male pipe to 1/8” female pipe


    I made my own pressure gauge and holder. I bought the NOS or Autometer adapter that you screw into the place on the fuel line where the schrader valve goes. You have to remove the Schrader valve, but save it, since you will reuse it. I ran a piece of SS (stainless steel) braided hose to a 1/8” pipe brass tee fitting that I mounted on the fender well by the MAF. I made a mount bracket out of aluminum angle I got from Home depot and bolted it to the fender well. Then I mounted the brass tee to it with some machine screws and a plate. I sandwiched the brass tee between the aluminum angle and a flat piece of aluminum that I trimmed off the extra aluminum angle. Three screws laid out in a triangle pattern go through both pieces of aluminum to clamp the tee in place. Put the Schrader valve in the spare port of the brass tee. I used a cheap industrial gauge from MSC Direct ( P/N 56468499). It works great and was cheaper than (less than $6) anything Summit had.

    If you look through the MSC Direct catalog, you can find any type of gauge you want, including liquid filled. You only need a liquid filled gauge if you mount it directly on the engine. The liquid filling dampens out the vibrations.

    You can buy the Autometer Stainless Steel braided hose for like $60. Or a local shop that makes hydraulic hose assemblies can make it for you at a cheaper price. Ordinary low pressure hydraulic hose can be used in place of the Stainless Steel braided hose, the Stainless Steel braided hose just looks nice. I got mine for $4 at a place that sells industrial and military surplus parts of all kinds. The Stainless Steel braided hose goes for about $3.60 a foot and the fittings are probably about $5-$8 each. You can make your own and save some $$$, the shops may have a setup or labor charge to fabricate the hose assembly.