2005 Dodge Neon OBD code 304

ACE26DAN

MEMBER
2005 DODGE NEON
4 CYL
FWD
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

4 Replies

MERLIN2021

MECHANIC
17,250 POSTS

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?

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Wednesday, May 28th, 2008 AT 1:47 PM

ACE26DAN

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2 POSTS

No valve train noise, and miss is intermittent, that has gradually gotten more frequent

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Thursday, May 29th, 2008 AT 4:31 AM

MERLIN2021

MECHANIC
17,250 POSTS

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!

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Thursday, May 29th, 2008 AT 4:12 PM

CLANMONROE

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1 POST

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.

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Thursday, August 21st, 2008 AT 2:24 PM