Long Tube Header Install=misfire/rough Idle.....help

Discussion in 'SN95 4.6L Mustang Tech' started by ch_stang_98GT, Aug 28, 2013.

  1. Hey guys, recently installed some pacesetter longtube headers on my 1998 mustang gt. To start off, it was the biggest pain in the a**. I didnt use pacesetters gaskets though, i bought sce gaskets. During the install i couldnt disconnect the egr tube from the manifold so i cut the tube and decided to delete the egr. I used a block off plate, capped the vacuum, and put a plug in the header. After all of this i have a misfire and its coming from the drivers side header. Did i incorrectly delete the egr? Could an exhaust leak be causing the misfire? Any feedback would be great, my car ran perfectly fine before the long tubes so i am at a loss....I am getting a new tune from sct tonight for the egr but im not counting on that fixing it. If all else fails i might just get new gaskets from ford to see if that does anything.
  2. did you disconnect the battery to reset the computer to allowit to learn the new setup
  3. You need to delete egr in the tune as well, car will overcompensate. Also, some cars need an adjustment in the oxygen sensors as you moved them slightly downstream. Also, if you have an exhaust leak pre oxygen sensors you will have misfires or chugging as the computer is trying to compensate for the extra air etc.

    Also, make sure you didn't burn through any o2 sensor wiring too.
  4. Thanks for the replys! Yes i did reset the computer, and my new tune is on the way so im crossing my fingers!
  5. I think all longtube installs require a tune. That will probably do the trick, unless you have a header leak.
  6. I think it has something to do with the EGR. I installed long tubes with no tune and ran them with out a tune for 4 years
  7. amen, i never tuned after i added long tubes with no issues
  8. So, with longtubes, do you have to turn off the egr or is there adjustment to keep it working correctly if he egr is still connected?
  9. No adjustment needed if you keep it functional as you should
  10. No tune after my LT's and still using the EGR.....zero issues.
  11. hey guys, tuned out my egr the other day.(when i did the LT install i was going to keep the egr but had to cut the pipe that attaches to the manifold because it was seized) Right now im running straight headers because im getting my exhaust welded up sometime this week. My car is still acting funny, on a cold start at idle it will idle fine, but once i warm it up and am in traffic it wont idle at all. I dont think its a misfire because if feels perfectly fine through all rpms. I have a bank 2 lean code also. Im doubting that its an exhaust leak, but it very well could be! Any feedback would be great
  12. so your driving a computer controlled car with half arsed deleted egr and open headers and wondering why the car isn't running properly? :shrug:
    95PGTTech likes this.
  13. Maybe from the ice cold ambient air meeting the 800+ degree open header exhaust directly next to the computer's primary way of measuring the amount of unburned oxygen in the header.
  14. maybe, but its an oxygen sensor, not an egt sensor :)
  15. i would guess you have a vacuum leak. did you try spraying starting fluid around your 'egr deleted' areas? i put long tubes on my car when it was still stock, and i drove it for 4 years with out a tune and no issues. i will tell you this, i had an old buick winter beater that had a plugged egr port in the manifold, when i finally got the port clean and disconnected the egr tube to try to clean out the egr valve, it ran like crap... it would hardly idle.

    you dont need a tune, you dont need to worry about your o2 sensors being downstream, start troubleshooting with carb cleaner or starting fluid... i suspect that you will find a vacuum leak somewhere.
  16. A tune won't fix that...it actually sounds like an ignition problem. Check your plugs and coil packs for damage.