Mechanics

OBD CODE 304

2005 Dodge Neon

Engine Performance problem
2005 Dodge Neon 4 cyl Front Wheel Drive Automatic 52,000 miles

I am getting a code 304, #4 cylinder mis fire, have changed plugs and wires twice, swapped plugs and wires to different cylinders, tested coil pack, it tests to spec, have plenty of fuel pressure, I clear the code, drive it, and as soon as it returns to idle the code comes back on, car runs fine at speed, 34+ mpg, but idles rough and the code, what next, injector,

Thanks,
Dan Whiles
AD
Avatar
Ace26dan
May 28, 2008.




Injector, yes test it by ohming the others and comparing the result, if it's OK check the compression in that cylinder. Any noise in the valvetrain?

Merlin2021
May 28, 2008.
No valve train noise, and miss is intermittent, that has gradually gotten more frequent

Tiny
Ace26dan
May 29, 2008.
You may have a vacuum leak, get a can of spray gumout, spray the vac lines and maniflod area, when the idle changes, youve found the leak! You want the engine running and spray on the outside but do direct the stream onto the hoses, if it is a vacuum leak, the engine idle will change speed, then you have detected a leak, repair the vacuum leak and see how it runs!
AD

Merlin2021
May 29, 2008.
Had same problem with a 4cyl jeep, found the injector gunked up (since it's at the end of the rail any gunk tends to be forced there) cleaned it out and ohm'd it out still had the problem, swapped injector w/ #3 and engine code went to #3 cyl. Replaced injector.

Tiny
Clanmonroe
Aug 21, 2008.

AD