Home › Forums › Stay Dirty Lounge › Service and Repair Questions Answered Here › 92 f150 300 6cyl. runs very rough,will not idle until warms up › Reply To: 92 f150 300 6cyl. runs very rough,will not idle until warms up
Probably 2 seperate issues. The new map can certainly be bad, but bad wiring or connectors could also cause this. A scanner can monitor signal during a jiggle test to help diagnose this.
The fuel pump could have a bad relay. Replace or swap the fuel pump relay with a known good one. If that doesn’t fix it, check the primary circuit at relay box. If you have voltage continually on the primary side the vehicle thinks it’s running or cranking. This can be caused by a bad or shorted ignition switch or PCM. Depending on the vehicle the ingnition module, crank or cam sensors will report that the engine is or is not running. The first thing to check though is the fuel pump relay itself.