[4boostin]

Originally Posted by Tech II

What year?

With the vac line connected, at idle you get a min fuel pressure........ when you disconnect it, fuel pressure should increase 5-10 psi......

Vac in line at idle should be around 18", with a gage.......

You have a misfire, so you need to find out which cylinder is misfiring......you have coil on plug setup.......one at a time, disconnect the harness to each coil.....there should be a noticeable drop in rpm........if there isn't, that is the cylinder with a problem.......

You put in new plugs....were they OEM? If yes, once you found the cylinder, that is misfiring, swap a coil with another cylinder.....if the misfire moves to the swapped cylinder, you need a coil.....if the misfire stays at the same cylinder, then try swapping a plug...if the misfire still stays at the same cylinder, you need to check compression.....you also need to check for a pulse signal from the PCM.....if all this checks out, you have a possible injector problem....

Thanks for the reply....
2004 is the year. Fuel pressure did not change when removing the vacuum line from the FP regulator. I don't have a vacuum tester. New plugs were OEM. The CEL is P0300 now since checking the FP and replacing the filter. I disconnected the front 4 coils, one at a time and it didn't change the rough running. The problem seems more fuel related, and I can smell gas, but not see a leak. The missing problem only started after checking the FP. Unplugging the FP relay to remove line pressure caused the engine to cough and sputter before stopping. Could that have done something??