Help me create the "Surging Idle Checklist"

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

  1. Bbq

    Bar ba que sauce
  2. WOOOOOHOOOOOOOOO!!!!!!!!! Thanks Jrichker, every one else!!!!! my Idle prob is cured!!! My mass air meter was filthy! and I needed a new IAC motor. The combination between the two really made a mess!! thanks every one for your all advice :nice:
  3. Well here is what I did to cure the surging idle.

    Pulled codes

    O2 sensors were going out so I replaced them
    Cleaned my IAC, TB and MAF and ACT
    Went around motor to check for vacuum leaks, found several specifically around throttle body to EGR spacer and upper intake. Used a can of starting fluid to spray around gaskets and hoses. Fixed all of my vacuum leaks.
    Car now pulls 16" of vacuum at idle

    Now the car idles pretty smoothly still a hiccup here and there. Might just go ahead and replace the IAC in the near future.

    A big thanks to jrichker for starting this thread and to Hissin for makin it sticky :nice:
  4. Here are a couple quick pics of an IAC with the port mod sitting next to a stocker and the air die grinder I do it with.

    For an elaboration on the o2's. The two white wires on the o2 sensor are for a the o2 heater. Without them working ,especially on longtubes the o2's cool off at idle and slow cruise and stop working correctly and the puter flips out. Use a paper clip or two and check for 12dvc between the two wires. No voltage, no heaters. Ford actually made a change and put the fusible link on the outside of the harness in the early 90's


    Attached Files:

  5. could a bad ground be cause for idle problems?
  6. Bad grounds in a computer controlled engine will make all sorts of strange problems.

    Here's the ground fixit test path...

    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. Any car that has a 3G alternator needs a 4 gauge ground wire running from the block to the chassis ground where the battery pigtail ground connects.

    3.) The computer has its own dedicated power ground that comes off the ground pigtail on the battery ground wire. Due to it's proximity to the battery, it may become corroded by acid fumes from the battery. It is a black cylinder about 2 1/2" long by 1" diameter with a black/lt green wire.

    4.) All the sensors have a common separate ground. This includes the TPS, ACT, EGE, BAP, & VSS

    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 in the fuel injector wiring harness and comes out under the throttle body. It gets connected to a manifold or head bolt.

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

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

    8.) 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.

    See for help troubleshooting voltage drops across grounds
  7. For the kind of idle that surges when the clutch is engaged, or stays the same when the clutch is engaged and then raises to around 2500 RPM at the stop in neutral, I used this site to fix my problem and IT WORKED! I had a combination of a filthy IAC valve and throttle body as well as ten pin connectors. Thanks very much for your posts, they really did the trick for me. I wish you all the best of luck with your idling situations.
  8. I went out to look for theses salt and pepper shakers, and found nothing. I have a converted 4cyl and I didn't swap the motor. My car idles around 750 with a mild cam, but idles crappy when its not warm. O2 sensors maybe? Also I have the battery mounted in the back and I only have one 4 gauge ground running to the battery (bolted to the intake manifold). Is that enough?
  9. Two thoughts:
    Ford had a TSB for this where they would do one of two things...they would put a 6 inch jumper harness in the salt and pepper shakers, claiming that they were perhaps too tight resulting in a bad connection. IMHO this is perhaps not the best idea because you are adding two new connectors to the mix and thus two new potential sources of problems. I took mine out of the harness I am working with.
    The other thing I know Ford used to do is put the IAB spacer in to allow for a little adjustment. If you go to a pick-n-pull salvage yard and paroose the Ford section, you might find one accompanied by a little yellow sticker somewhere under the hood. These help to get a little more air in and they are adjustable. Should be a Ford service part availiable from the dealer...they have a Ford p/n on them.
  10. Fix= Bad 02's/dirty 02 harness, Dirty MAF, Dirty IAB, Dirty TB.
    Awesome thread.
  11. anyone know the ford part number for the idle adjustment plate?
  12. I will look around for it.I bought one and put it on,my idle shot up to 1500rpm,,LOL,,I gave it to some guy on this web site.I'LL let you know by tomorrow if I find it...JRICHKER,,I have an idle problem..Just started happening,I just cleaned out my IAB and it still happens.When I start it in the morning it revs past a 1000rpm's then stalls..On the 2nd try it idle's fine..When its warmed up it idle's fine too(no surge) but if Im at a light or stuck in traffic it will be fine for 30 seconds then the rpm drops way down,,it stalls when in drive,if I put it in nuetral it idles at like 550-600rpm..This always happens now,,any ideas?(Its an aod,stock motor with bolt ons)
  13. Willys, thanks anyways but I found it and ordered one. should have it today or tomorrow. I'll post up my results.
  14. Awsome :nice: I couldnt find it,but someone here on SN gave it to me so I knew it would show up!!,,My idle seemed fine today..I guess it needed a full cool down to compinsate for the cleaned IAB :shrug: But it still stalls when I start it in the morning.....This thread is a great idea :nice:
  15. Well its back again :bang: Everything was fine until I nailed it from a stop to 80mph..Then when I got to town it started in again,only now it doesnt go away :shrug:
  16. Check & clean the IAB electrical contacts & the 10 pin connectors too. If that doesn't fix it, I would look into replacing the IAB. The cold stalling is a clue to a non-functional IAB.
  17. Hey guys, I read through the posts on this subject and I used the some of the technics to help find my gremlins.
    Thanks, Joey.
  18. $7 fuel filter, now my car runs smooth as silk... All this time it's been the freakin fuel filter... :(
  19. My 89 LX idles right at 900-1000 steady on a cold start.....closed loop.
    As soon as it hits operating temperature it starts bouncing 700-900 rpm.
    From there the idle sort of "bucks". Soon it becomes such a "buck" that it stalls the car. I have an E-303 cam and i know someone mentioned that they are notorious for that problem.
    Now that i know the problem is only in "Open Loop" operation, is there anything i can eliminate right off the bat as i try to trouble shoot?
    It can't be a vaccum leak or it would happen in both open and closed loop, correct?
  20. I might be loopie (well, we know that), but I think you have your loops backwards.
    OL is when O2's are not used (Cold motor, WOT, etc).

    CL is when the motor is warmed up a little and O2's are used.

    I wanted to make this distinction - people who reply would probably want clarification. good luck.