5.0 hits a wall when WOT

Discussion in 'Fox 5.0 Mustang Tech' started by Mustang5L5, Oct 5, 2009.

  1. Okay, so this has been an ongoing issue for some time with my car. It did it when it was AOD, now it does it with the 5spd.

    When i go WOT through 2nd or 3rd, the car hauls like a raped ape up until about 4000RPM or so, where it feels like someone flips a switch and i instanly lose 25HP up to redline. It just falls on it's face. But it's a definite immediate transition, you can feel it lose power like flipping a switch

    I've done the usual checks, new plugs, cap, rotor, timing at 10, no codes, FP stays high at WOT, car is still speed density, no vac leaks. Other than this issue, it runs great.

    I'm just wondering if i should start looking at the dizzy components for such an issue? Any other ideas where to look? I need a fresh angle
  2. Are there any inlet or exhaust restrictions which would choke it off?
  3. The Distributor is where Id look. A messed up TFI or PIP can cause this. Usually in the TFI, since thats what recieves the Spout signal. If the TFI skews the spout signal, it will act like its not recieving the proper advancment from the ECM when it signals the Coil to fire.

    Not saying its your problem, just seen it happen.
  4. I didn't suggest ignition components since it was not noted to occur in all gears. But if doing so, I'd add to Joe's list that a failing coil (and plat plugs, which I know you don't run Mike) can cause a 4K RPM drop-off.
  5. Well, it could be doing it in 4th gear. I haven't get gone that high WOT since i usually get upset with the performance in 3rd gear. It could be doing it. I am not sure it does it in 1st because with 3.73's, i'm shifting to 2nd before I have time to even notice.

    Coil is an Accel coil i got a few years back. Wish i kept my stock coil as i'd toss it back on just to see. Plugs are copper motorcrafts as usual :)

    It really does feel like an ignition sort of thing...i just don't want to start replacing parts if i'm not sure it's the reason. I was leaning towards the dist. related parts myself.

    I am running a stock 55mm MAF meter in my cold air tube...just because. The car is still SD for now, but i have a Ford 70mm MAF going in soon. Not that I expect that to be the reason.

    It's definitely not as fast as it should be. It's losing power up top somewhere.
  6. I'll have to swing by the car and take a look inside. Last i remember it looked fairly clean.

    This is an original untouched 21-year old dist. I've never replaced either component, so i wouldn't be surprised if something was on it's way out
  7. Just to add to the list since a few things can cause this problem.Run the standard KOEO test. I'm also with HISSIN50 on the coil, a bad coil will flatten the motor at higher rpms and since you have one it's easy to rule out. Mike you still running cat's on your exhaust? you may have partially clogged exhaust (too much back pressure) as culprit a simple vacuum test would tell you. some other things to look at clogged fuel filter, weak fuel pump( test FP under a load might not be able to keep up with fuel demands at higher rpms), hall effect in the dizzy, etc. also look at the plugs.
  8. ive got the exact prob except it also wont start and i have to jump the solenoid to start the car. i was going to start looking at dist things also. just need the time. is it also weak for the first few minutes after start up. just wondering if we have the same prob.

  9. Well, i don't have a stock coil anymore. So i'll need to borrow one or see if i can find one.

    Yes, i still have a stock 4-cat hpipe. I had an off-road, but it fit like junk and hated the no cats thing, so on my list of things to get is a high flow midpipe.

    Fuel filter is brand new, pump is original but have 190lph in box. I do have a cowl FP gauge and it does not fluctuate when the "wall" hits. It's done this also on two different sets of copper motorcraft plugs.

    Guess i have some things to be testing now.

    Car runs great at idle and driving around town. It's just when i try to go WOT for a few gears that i find it hitting a wall in the upper RPM's. Best way to describe it is the opposite of VTEC. It hits a certain RPM and something changes and i lose power.

    Just checked pricing of new FORD parts @ rockauto.com

    Ford TFI $100
    Ford Ignition Pickup $60

    So i def don't want to replace unless I have to
  10. Ive been running the El Cheapo, TFI's and Pick Ups. No problems here, but Ive seen my share of New but no good stuff from the Auto Parts stores.
  11. electrical stuff, I like ford oem. Mike if you get the TFI tested have the test run few times to heat it up (I have seen a bad tfi pass) if you need I have a good oem TFI & oem coil I can send you that you can borrow if you want, just send them back to me when you are done. If you lived closer I would pull my dizzy and throw it in your car to see what happened, the option to come out to my place is offered if needed also.
  12. I have a extra stock coil if you need it, just PM me. No charge, just need your address
  13. What parts chains can test the TFI?
  14. Advance auto, autozone like cenok is family stated and some napa's I believe.
  15. it depends on if they have the equip or not. none in my area have any.
  16. Thanks guys, i'll def have to test the TFI and pickup shortly. I really don't want to just blindly toss money at it right now as i'll be parking the car for the New England winter soon and my DD needs some routine maintenence before the winter comes so I'll need to spend some money there.

    Chris, i'll let you know if i need to take you up on borrowing a TFI. I'm going to work on "Project Fallen Hero" this weekend so i may be able to borrow that entire distributor if it's at the shop. If not i'll give you a PM. I want to park the car by Nov (give or take) so i'd like to solve this before then. Thanks

    1993SSP, PMed about the coil
  17. They cant test the Pick up as far as I know.

    The link I posted gives instructions on how to test the Pick Up. Real simple.
  18. No problem Mike just let me know.