1989 Gt Half Throttle Stumbles And Chokes After New Exhaust

Discussion in 'Fox 5.0 Mustang Tech' started by jimvanderl, Apr 23, 2014.

  1. My friend bought a 1989 5.0 GT. It had no cats just a pipe to a pro chamber and 2 stub exhaust pipes. The engine is stock. It ran great when he brought it home. Then he had a new exhaust system put on, they "forced" him to put cats on. As he drove away from the shop he found the engine won't run at over 1/4 to 1/2 throttle. At rest it will rev free if you just roll on then seems to choke at about 1/2 throttle. If you are driving and the engine has to pull a load, it dogs out about 1/4 throttle.
    We are sure its related to the exhaust but not sure where to start. It was built with cats so why isn't running right? Its back to stock, new plugs, wires, etc. we disconnected the battery for a while to see if the ECU would reset but no change. No codes. Any ideas out there?
    #1 jimvanderl, Apr 23, 2014
    Last edited: Apr 23, 2014
  2. Not even a code 11? The koeo koer tests should give some response, even if it is just the All OK code.
  3. Unhook exhaust at headers and see if it is fixed. If not or before that try a light tap on the top of the TPS sensor. I had one act similar once with a bad TPS.
  4. You got some good advice here and it is the first thing to do....
  5. Welded exhaust i assume?

    Possible if the batt wasn't disconnected some damage was done to the ECU