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1st Gen Neon 1995 through 1999 Neons

P0300 ENGINE MISFIRE CODE

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  #1  
Old 08-17-2005, 11:10 PM
JIMDODGE
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Default P0300 ENGINE MISFIRE CODE

I have a 1996 Dodge Neon with 58,000 miles. I have replaced the spark plugs and spark wires with no change in error symptoms. Engine drives smooth. I can drive 2 to 50 miles without the error code but then it will popup. When the engine check light comes on, there is no change to the running of the car.i.e, there does not make any sense that the ignition coil is damaged.
Unplugging the battery cable erases the error code but it will reappear sooner or later.

Any help would be greatly appreciated.
 
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  #2  
Old 08-22-2005, 08:34 AM
RadarLove
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Default RE: P0300 ENGINE MISFIRE CODE

The coilpack can develop hairline cracks that will only become a problem as it gets warmer. Might even test fine at the shop (when cold). So I wouldn't necessarily rule it out completely...

The PCM determines a misfire by keeping track of crankshaft speed. If it drops a little from what's expected and then picks back up, it assumes the plug didn't fire correctly. So in addition to the coilpack, you may want to check and/or replace the crank sensor (or just make sure it's tightened down). Check the wiring to the coilpack and crank sensor as well to make sure it isn't rubbing up somewhere and grounding out or being pulled tight and causing intermittent opens.

The cam sensor doesn't come into play in ignition control. Two plugs fire at a time - one at the top of the compression stroke like normal, the opposite at the top of the exhaust stroke. You can unplug the cam sensor and that won't change...

The MSD coilpack tends to be the cheapest out there. Dealer prices run $70-120 depending on where you go. Parts stores run $80-100. And Summit Racing has the MSD for $75. No performance advantage from any coil available.

Crank sensors run $75-100 from the dealer, a little less at a parts store.

Frankly, I'd put my money on the coilpack still. Mine is still the original with no issues after 237k+ miles now. But I know mine's not typical. For every one like mine, there were a dozen that didn't make it to 100k miles.

Best of luck!
 
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  #3  
Old 08-22-2005, 02:06 PM
hemipower1984
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Default RE: P0300 ENGINE MISFIRE CODE

i have fixed a couple of tese by replaceing valve springs. they have a new style spring that is stiffer. applies more tension. the weak springs can cause the misfire.
 
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  #4  
Old 08-24-2005, 07:33 AM
RadarLove
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Default RE: P0300 ENGINE MISFIRE CODE

Ummm, again, 237,000+ miles, original "weak" springs... The only time I notice them is above 7200 rpm and they start floating. Even then, no misfire code, ever... never heard of it on another Neon either, at least not with the stock rev limiter.

 
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