Expert: Roland Finston - 12/7/2011

Question
Hi Roland,  I have a 2004 dodge neon, I have replaced the following:  crank shaft position sensor, spark plugs, wires, coil, tp sensor, fuel pump, and 2 other sensors and my check engine light is still on.  I have a 2.0 engine the other day i was parking my car and my key was stuck in the ignition w/a code of P0300 what would cause this?  I have spent more money on this car within the last 4 years can you please help.

thank you,

Answer
Hi Michele,
That is the code for multiple cylinder misfire.
Unfortunately there are many (17) possible reasons for the misfiring of an engine on all cylinders. The manual lists them and gives an 18 step precedure for identifying which is the cause. I can copy that and attach it to an email which I send to you directly. To do that you need to tell me your email address as I am not shown it by Allexperts. So ask a NEW question (not a follow-up) and check the box to keep it PRIVATE. Then in the text area list your email address.
How is the engine running, otherwise than for the check engine light? How many miles are on the engine?
The 0300 code is logged when the rpm varies just slightly from a constant reading, so you may not notice it. May I suggest that you continue to readout for fault codes, using the ignition key:"on-off-on-off-on and leave on" doing that in 5 seconds or less elapsed time. Then watch the odometer for any new codes and let me know what they are.
The possible causes that would not produce a code are:
variation in the compression readings of the cylinders (you might have that checked),
a clogged intake air filter (you might check that visually),
partially clogged fuel injectors (you might put a fuel injector cleaner in the tank)
or excessive oil consumption (how often in miles do you have to add oil?)

Roland