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I am having a problem with a p0304 code (engine misfire cylinder 4). I can reset the code and the car will run without a problem for 100 or so miles and then come back on. There is no sign of a miss. Intermittently the check engine light will flash if I am at a stop but it goes away once I am driving.

The car runs well but has a rough idle after warming up. This morning when the code came up I also got a P0441 code (evap). Seems the evap code could be a false code related to the misfire.

So far I have changed wires and put fuel injector cleaner in the car.

Any suggestions on what to check next? This is a puzzling problem since I can clear the codes and drive for a few days without getting the code.

what year neon?
check your coilpack as they can go bad, is there any oil in the #4 spark plug tube?

It is a 2004 SRT with 135k on it. No oil on the plug. It looked very clean when I pulled it out Sunday. I did regap the plug since it was about .40 and changed it to .35.

I have meter and will pull the coil off tonight to check that. I am also going to switch the plugs from 2 & 4 to see if the problem follows the plug.

Sorry, not sure what I was thinking. My Neon is a 2003 SXT. Definitely not high output or turbo.

lol, yeah if the coilpack seems to be ok, try swapping the injector around to see if the missfire follows the injector.

Good thing you dont have an SRT. That gap is smaller than stock.
Normal Neons are gapped to .035" .35 is almost 3/8". That zero makes a world of difference.

Lol... .35 would be a big mistake..

I plan on pulling the coil tonight and testing... anyone know what the settings are? I have a Haynes at home so hopefully it has the primary and secondary spec's for the coil.

The problem seems to be very intermittent since the CEL only comes on after I drive the car 50-100 miles. Today the CEL came on after 117 miles of driving..started solid then flashed while stopped..went back to solid when I started driving.

Could the coil get hot

not sure what happened but my keyboard locked.

Could the coil be getting hot and after time cause a misfire? Since cylinders 1 & 4 are on the same side wouldn't both misfire? Just doing my homework to understand how they work.

yes, its actually what i was thinking, its failing under heat. Typically you're right the whole coil fails but i've seen weirder things happen.

Pulled the coil tonight and tested it. Question- how do you tell if you have a brass tower vs metal tower? My Haynes gives measures for both types.

The readings were:

Primary
1-4 coil = .7 - .8 ohm the meter kept fluctuating and would not go to 2 decimal points
2-3 coil = .6 ohm got a few reading of .7

Secondary
1-4 = 13.35
2-3 = 13.22

Thoughts on this? I am going to bring home a different meter from work tomorrow that hopefully can read lower than the one I borrowed from my buddy.

Also, tonight on the way home the car drove great but when I got off the highway it idled rough and I got a code that blinked for a minute but went completely away when I started driving. At the next stop the idle was not as rough and it did not set off a code. Got a P0304 and P0441 (evap). My thought is the evap code was from the rough idle.

Thanks,

Tim

A little more info.

Drove to work this morning.. No code until I got off the highway after driving 25 miles. CEL flashed then stopped after I started driving. Idle was a little rough. Check for code when I got to work and it was again cylinder 4. I drove another 2 miles to work stopping at 2 more stop lights but the CEL did not come back on and the idle seemed to be a little smoother.

When I pulled the code the scanner has a freeze frame option. The only thing I noticed was the RPM was 273 when the code flashed. If it helps I can write down the readings the next time the code flashes.

Any thoughts?

Anyone?

This is WAY off the wall here...
have you replaced your timing belt? I just went throuh this the belt did not break but sheared teeth off the belt. I wonder if your are having misfire due to being out of time? My '04 had 133,XXX miles. PO did not change TB at the scheduled 100K mark... Lucilly I did not bend any valves when it went.

Timing belt was changed out 20k miles ago. Did the water pump at the same time.

I swapped injector 3 and 4 tonight. We'll see if the problem moves cylinders.

Well good for ya... just thought i would check...

I appreciate any/all suggestions. You never know when you might be overlooking something.

Did the problem move?
Have you also tried swapping the spark plug wire from #1 and #4?

I moved the plugs around a few days ago and the problem stayed on #4. The wires are new so I haven't moved them around but I guess I could have gotten a bad set of wires.

I changed the injectors last night and so far no code. In the past I reset the code and drove 100 miles before it tripped again.

I rechecked the coil last night and found that 1-4 coil fluctuated from .7-.9 ohm's while 2-3 coil stayed at .6 ohms. I haven't found a multi-meter that will read down to the hundredths required to get a 100% accurate reading. Is it normal for the reading to fluctuate when you put the probes on the coil? The secondary readings were pretty solid so I am confident they were accurate.

Last night the readings were:
1-4 coil = .6-.9 fluctuating... mostly stayed around .7
2-3 coil = .5-.7 fluctuating... mostly stayed around .6

Let's see if it comes back.

Ok, moving the injector to cylinder 3 did not fix the problem. Check engine light back on for P0304. That leaves the coil or a valve issue.

Question.. if it was a valve would it not be a constant issue? Strange that I can reset the code and it seems to only kick at a stop light after having warmed the car up and driving for a while.

I am going to borrow a pressure gauge so I can check each cylinder but hopefully that would not be the problem.

If the computer is starting to fail, could it show symptoms like this? persistantly only one cylinder misfireing??? sounds kindof fishy to me. Maybe you have a ground somewehre in the ignition???

Yep. Only getting a code for cylinder #4. The coil seems like it might be the problem since testing shows it to fluctuate between .6 and .8, mostly at .7 when I put the multimeter on it. Cylinder 2-3 coil test consistently between .5-.7, mostly at .6.

Try swapping it with a junkyard coil.

On my way to the junk yard this morning. Hopefully that solves the problem.

I also now have to change out the tensioner pulley for the serpentine belt. When it rains it pours with this car. Hopefully changing out the pulley is a simple task but my guess is it will be an adventure.

See this - might make your life a little eaiser gettong the belt off and on >> viewtopic.php?f=40&t=371171&p=3076027&hilit=tensioner#p3076027