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car finally gave codes while running rough

09-12-2009, 12:14 AM
1999 Plymouth Neon SOHC Automatic 127,000 Miles

Starts hard, runs rough at idle (sometimes)

P0300 - random cylinder misfires

P0302 - cylinder number 2 misfire

Car has new:
spark plugs
spark plug wires
cam sensor
coolant temp sensor
ignition coil

-Was told possible corrosion under coil - there is none but I cleaned it anyways

-Was told possible High or Low fuel pressure - will check that this weekend

-Was told possible bad compression - will check that this weekend

Anything else I should check or replace?

09-14-2009, 11:57 PM
alright checked the compression and it is good and all are within 10% of each other.

Fuel pressure is right on with 47 not running 38 running.

For *hits and giggles I unwrapped as much wiring as I get too without taking too much apart and checked it for breaks, frayed wires, melted wires but again everything checks out.

Im wondering if the new coil is bad.

cylinder 2 is almost dead at idle and cylinder 3 unplugged changes the engine a little. unplug cylinder 1 or 4 and the engine dies.

Pulled the plugs and they are all in good shape no oil or anything.

Injectors are all good as I swapped 1 & 2 with each other and 3 & 4 with each other and still 2 is dead and 3 is almost dead.

I know they all spray because i pulled the fuel rail with them on it set it upside down and they all sprayed perfect.

also while driving along at highway speeds it sounds like the engine is back firing once and awhile.

Any ideas?

still getting a P0300 and P0302 Code after I take it out driving.

09-15-2009, 01:45 PM
Just because a part is new doesn't mean it is good. Coil is a possibility. 1 and 4 are paired and 2 and 3 are paired. Black wire with grey tracer is for the coil driver.

09-15-2009, 08:09 PM
Checked the resistance of the primary and secondary coils and they are within specs.

so its not that.

pulled the battery cable for a few hours put it back on drove about 40 miles no codes.

still runs rough at idle :banghead:

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