Help Me!!!

Discussion in 'Fox 5.0 Mustang Tech' started by EricS 91gt, Jun 23, 2013.

  1. Ok so here is my problem, I put headers, plugs and wires along with a h-pipe on my 91gt and with no pipes and it drove fine with all power... so here is where the problem starts, I got a guy to weld side pipes on it. I got the car back drove it home and floored it and it had no power. I pulled all the plugs rechecked all plug wires and still nothing. I replaced the tps, aic, act sensor, the ecm, maf, and the fuel filter.Took off the upper and lower intake cleaned them both and still nothing. The car is stock besides the fender mount and others I mentioned. My brother and I are both stumped. Btw its an auto. What stumps me is the only defining thing is the side pipes. Thanks in advance.
  2. pull yer codes. many stored codes do not trigger the cel but will tell you whats going on
  3. Ok will do asap. Thanks
  4. Ah. It's obvious that the car doesn't like the side pipes. They know man. They know.
  5. Lmao... I was gonna cut them off just to see if anything happened lol.
  6. Dump the codes: Codes may be present even if the Check Engine Light (CEL) isn't on.

    Dumping the computer diagnostic codes on 86-95 Mustangs

    Revised 26-July-2011. Added need to make sure the clutch is pressed when dumping codes.

    Codes may be present even if the check engine light hasn’t come on, so be sure to check for them.

    Here's the way to dump the computer codes with only a jumper wire or paper clip and the check engine light, or test light or voltmeter. I’ve used it for years, and it works great. You watch the flashing test lamp or Check Engine Light and count the flashes.

    Post the codes you get and I will post 86-93 model 5.0 Mustang specific code definitions and fixes. I do not have a complete listing for 94-95 model 5.0 Mustangs at this time.

    Be sure to turn off the A/C, and put the transmission in neutral when dumping the codes. On a manual transmission car, be sure to press the clutch to the floor.
    Fail to do this and you will generate a code 67 and not be able to dump the Engine Running codes.



    If your car is an 86-88 stang, you'll have to use the test lamp or voltmeter method. There is no functional check engine light on the 86-88's except possibly the Cali Mass Air cars.


    The STI has a gray connector shell and a white/red wire. It comes from the same bundle of wires as the self test connector.

    89 through 95 cars have a working Check Engine light. Watch it instead of using a test lamp.


    The STI has a gray connector shell and a white/red wire. It comes from the same bundle of wires as the self test connector.

    WARNING!!! There is a single dark brown connector with a black/orange wire. It is the 12 volt power to the under the hood light. Do not jumper it to the computer test connector. If you do, you will damage the computer.

    What to expect:
    You should get a code 11 (two single flashes in succession). This says that the computer's internal workings are OK, and that the wiring to put the computer into diagnostic mode is good. No code 11 and you have some wiring problems. This is crucial: the same wire that provides the ground to dump the codes provides signal ground for the TPS, EGR, ACT and Map/Baro sensors. If it fails, you will have poor performance, economy and driveablity problems

    Some codes have different answers if the engine is running from the answers that it has when the engine isn't running. It helps a lot to know if you had the engine running when you ran the test.

    Dumping the Engine Running codes: The procedure is the same, you start the engine with the test jumper in place. Be sure the A/C is off, and clutch (if present) is pressed to the floor, and the transmission is in neutral. You'll get an 11, then a 4 and the engine will speed up to do the EGR test. After the engine speed decreases back to idle, it will dump the engine running codes.

    Trouble codes are either 2 digit or 3 digit, there are no cars that use both 2 digit codes and 3 digit codes.

    Your 86-88 5.0 won't have a working Check Engine Light, so you'll need a test light.
    See AutoZone Part Number: 25886 , $10

    Alternate methods:
    For those who are intimidated by all the wires & connections, see Actron® for what a typical hand scanner looks like. Normal retail price is about $30 or so at AutoZone or Wal-Mart.

    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-$36.
  7. something tells me going from your closed system with a h pipe to side pipes got rid of all your back pressure and you now have no power

    Sent from my iPhone using my fingers
    f8tlfiveo likes this.
  8. Automatic with straight pipes? That's why.

    No cats and no mufflers right? What you did was shift your power curve up eliminating a lot of low end torque. Reconnect your exhaust to your muffler and you should get your power back as you gain low end torque.

    Had a buddy run his stock 89GT to a 14.7....then he put straight pipes on the car with dumps...ran a 15.5 later on. Only change was ditching the cats/mufflers
  9. Ok so I borrowed a obd scanner and it couldn't read because it couldn't control idle rpms or something like that. So now gonna check that. As far as the back pressure issue, I drove the car with only headers and the h pipe and the car ran fine. It didn't start til after the side pipes were put on.
  10. on a 91? use a paperclip. scanners are a waste of money on that year mustang.
  11. Working on it now
  12. sidepipes? Didn't those go out in the 70's with shag carpeting on the dash and Keystone Klassic wheels?
    hoopty5.0 likes this.
  13. They come out behind the doors, not running along the side.
  14. Blast from the past.... my first Mustang was a black 67 that I blew up the 289 and swapped a 428 into. Had the thrush sidepipes and all.. lol Looked like this one. those stupid sidepipes hit every dam bump on the rode. But they sure helped to melt the snow in the winter...

    EricS 91gt likes this.
  15. Mine are under the car and just come out at the door. This is my third fox and I wanted a different look and sound. I got the codes. My bro is checking them. Thanks guys