Idle Problems.. new thread for problems

Discussion in 'Fox 5.0 Mustang Tech' started by savegoodautonfg, Jul 31, 2007.

  1. My old thread on this problem is here :

    I'm starting a new thread because the first few problems i had when i made that thread are gone.

    I have replaced:

    1. TPS
    2. Stock Throttle Body now back on
    3. IAC
    4. Fuel Injector Harness (great shape used one off ebay) because i had a problem with the ground off of this harness.
    The replacement was in great shape. took about 2 hours to install with little breaks in btwn. i fired the car up and still running rich and its still idling like i have a lopey cam in it. i dont understand.but now when i play with the wires it doesnt effect the idle like it used to with the old harness. so that's good but i still dont understand.
    5. Cleaned EGR Valve
    6. Cleaned MAF Sensor
    7. ECT and ACT

    Car continues to want to die when you first start it up after sitting for a few hours.

    If i set the TPS to .98 to 1 and then i try to set the idle with the idle screw at the TB, it will idle at about 700rpm and it sounds like **** and then if i try to make the idle be at like btwn 750-900rpm i can't do it wen i turn the screw it stays at the 700rpm point and then jumps to 1000-1100rpm. its really weird. any reasons for this..

    this harness doesnt have a ground issue anymore, but the idle problem is still there and i thought it would of been gone after the harness change.

    Yesterday I cleared codes and im going to drive it today and tommorow or so and hopefully i get some codes when i check them. just wanted to make this new thread to help clean things up a little bit cause my old thread some of the problems are gone so.

    Also to add I've went thru the surging idle checklist before i changed the harness out and i did everything it said and im still having problems.
  2. What was done to the motor when it was rebuilt? Who did it? What Heads, Cam and Intake on the motor? What MAF is on the car? Can you swap out the BBK CAI with the stock air box to rule that out? Have you checked meticulously for vac leaks?
  3. Iv had teh same problem but my car would die at tiems then it would go from a like 500 RPM idle to a 2000 it ended up being ECT ACT and teh Fuel presure REG was sucking in raw fuel through the vac line i found that casue i took off the line and it was a litle rainy out and i was liek oh dam cant have water gettin in there ha smelled it and i was liek wait thats GAS it was a New out of the box holly adjustable never returened it eather =( $50 hah also check codes! should never throw new parts at the car can cause mroe problems soemtimes ha check Jrichkers posts on how to if you dont already know

    Also did you reset the comp after doing the TPS after changing things liek that you should take off the Batt ground cable for like 10 mins and then try it again
  4. I got a rebuilt long block from PromarEngines in NJ. The website is

    I've heard very good things about them.

    The motor is stock. The stock MAF is on the car.

    I can't swap out the BBK CAI because I dont have the stock air box. But i doubt that is the problem because it never had a problem before.

    I have checked for vac leaks. Not only do i not hear any vac leaks but i changed most of the vac hoses to blue silicone hoses that this guy on ebay sells. great product by the way.
  5. I'm gonna try the comp reset in about an hour. get back to you.

    I have the stock fuel press regulator.
  6. just a shot in the dark but have you replaced your tfi module on the distributor? it causes stumbling and richness since the ignition isn't working properly.
    although in my case, i think it barely ran BETTER after sitting because the fuel had time to dry before becoming saturated again causing more stumbling. its something to consider tho.
  7. Before replacing this, is there a way i can test it to see if its bad?

    Also is it easy to take off?

    What do you mean by the ignition is'nt working properly? why do you say that?
  8. i'm by no means an electrical expert and know what i know through trial and error like most. i know its a solid state electrical component but i don't know if there's a test for it. call an auto parts store to see if they can. i'd say borrow a friends whose car runs fine. its that flat thing attached to the distributor with all the wires hanging out of it. its flat and rectangular ang its got a thick dielectric grease sandwiched behind it. hence the name thick film ignition module. its a pricey little sucker for a good one and of course i'd recommend a quality one cause most cheap ones don't last! i really hope this helps.:nice:
  9. My guess it the CAI is causing air turbulance issues with the maf...just MO at this point.
  10. and yes, its very easy to change. plug and play from what i remember.
  11. So what do i do about that dman?
  12. i'd like to hear D's response too actually. that is something i'm not personally familiar with and it may be helpful to know. it looks like you've covered alot of bases and here's two more you can potentially rule out. at least the tfi is something easy to check out or possibly rule out.
  13. Some meters are just plain finiky...the bend before the meter can cause turbulance, result is meter sees incorrect info and attempt to over compensate...result is a/f out of whack. This is most common with the PRO-m bullet and C&L meters...but can ocurr with even stock meters under some circumstances.
  14. So what would i do about that though?

    Yea i have the stock meter?
  15. Dman, I also asked those questions about the MAF and CAI earlier b/c i also suspected some wierd air turbulence issue. However, he says he's running the stock meter and he didnt have these problems before. This would lead me to believe thats not the you dont have that problem very often with stock meters.

    Poster, when exactly did these problems start occuring? what mods did it follow, or did they just begin out of no where?
  16. ah, i see. the air is coming through but at fluctuations basically, so smooth the airflow however possibe so its a steady airflow. check out the intake tube for starters i assume. if that were the case i mean.
  17. I always had some sort of idle problems. It was idling pretty good when i had my bbk 70mm throttle body on but it whistled like hell and i hated how it sounded so i took it off. Even with the bbk it did'nt idle that great.

    I bought a used Stock Ford throttle body off ebay from a reputable seller in good shape. put that one on and now i cant get the idle that good at all. its decent. its sounds ok. It's a little better after i just finished doing jrithcher base idle reset. but i dont understand when im parked in my driveway not moving and i start the car and i rev it up it slows down and stops for a second at like 1,200 rpm and then goes back to base idle.

    it also flutuates sometimes also.
  18. have you tried anything that was run by you yesterday yet? its heartbreaking when your jonesing to drive. i'm on my fourth fox, i've had my fair share of crap.
  19. Poster - When you say you rev it up, and it comes back down to 1200 for a second, and then down to the base idle, that sounds normal to me. Not trying at all to say you don't have a problem. In neutral sitting still if I rev it up, the idle drops back down to around 1300 for a few seconds, then falls to my base idle around 850. Just throwing that out there. Hope this helps in some way.
  20. Ok so if that's normal then get that out of the way forgett that problem.

    thanks for your input.

    but im still stuck with why it sounds like my car has a lopey cam in it when it doesnt.

    I tried the TFI from a friends car and it didnt work.