[HELP] Car surges after switch of midpipes

Discussion in 'SN95 4.6L Mustang Tech' started by Twista, Jun 2, 2009.

  1. I have stock headers, mac o/r H and mac catback. Already resetted the cpu by unplugging the battery.

    So, i switched midpipes many times before and this is 1ST time this has ever happened.

    So, i had to swap my mac o/r H pipe out for my mac catted h and everything went as planned expect the gasket wasn't :shrug: holding like it should. Anyways, the car developed a nasty leak, but i took it for the emission test anyway and passed.

    Fast forward to today i went and brought a new gasket from ford and put back on my Mac O/r H. The surging problem is still there :mad:

    It happens when you take off from a stop. The 1st couple rpms the car is like bogging down and surging and you can hear it and feel it.

    Downshifts than accelerating it the car is normal.

    The only thing i messed with was the rear o2 sensors.

    Does this sound like an exhaust leak somewhere? If so, i cant hear this baby.
    What could a exhaust leak damage? The o2 sensors???

    Damn it.!


    edit: while this was happening with the catted midpipe on.. there was no MIL OR CEL ON. NO CODES
  2. An exhuast leak before the upstream o2's will cause the puter to think its lean (unmetered air in the system) and there fore it will actually inject more fuel. That could cause a bucking issue down low.

    What codes is it throwing now if any?
  3. Not sure of the codes, but im sure im throwing the no cat code. So i will take apart the mid again and try re-seating it.

    I pray this is the problem.

  4. before you tear it apart check and make sure your o2 sensors are plugged in well and making good contact
  5. Link is blocked.... What does it say?

  6. ..........
  7. There could be damage to an 02 sensor or the connecting wire. I'm surprised you are showing no codes. I just installed my first midpipe and I can see where some damage could have been done. Try to pull codes if there's any. Pearl02.
  8. I just brought 4 new sensors, but there being shipped. So what would happen if i unplugged the sensors and test it? Or does the car need the sensor for it to operate somewhat properly?
    Just wondering if i unplug the 2 front ones would the car drive normal if they are faulty?
  9. If you unplug the front sensors you take away the cars ability to "adaptive learn". That means it cannot make on the fly fuel adjustments to get the optimal performance and mileage. The rears will not cause what the link above eludes to. The rear o2's Simply tell the puter if the cats are working or not, w/o cats or mils you will get a rear o2 code..... That will not affect performance whatsoever. With that said, if your fronts are bad if can cause all sorts of crazy stuff to happen. Not likely that both fronts went at the same time unless you caused damage to them when removing and reinstalling.

    Never hurts to buy new o2's but I fear this likely won't solve ur issue.
  10. I think i got the problem pin pointed, just i cant access the sensor. So i guess driving with the bad exhaust leak on the passenger side somehow sent the soot to my air flilter which is black and gunky nasty. So, with that said.. my MAF has to sooted to hell. I brought some MAF cleaner but i have to buy a t-20 female torx =[
  11. Not sure an exhaust leak can dirty up an air filter. But the would def cause the issues your talking about.
  12. well i had no gasket on the passenger side which is required or else it would leak bad. :shrug:

    I just brought the torq so will clean the MAF today and pray it helps
  13. Yea no gasket will cause one big leak but how the hell did it dirty up ur air filter? Those two are a long ways apart. Is it an engine bay filter or is in the fenderwell. If your filter is that dirty then your whole engine bay must look like a chimney..... :D
  14. =[ nope that didnt fix the problem. So, next ill check the throttle body and clean it. Than the spark plugs and wires..

    Than the fuel filter, but that was changed about 3 years ago =]
  15. DON'T CLEAN THE T/B.........

    It has a coating on it that most cleaners will take off and cause horrible idle issues..... fyi. wipe it with a dry rag at best..(or use a t/b safe cleaner).
  16. If i bog the engine on purpose by shifting to a high gear @ 2 low speed.. the car REALLY and i mean REALLY sputters and hesitates.

    Does this ring a bell to anyone?
  17. just got done fixing the problem :nice: I changed the spark plugs/wires and the problem is gone.