Check Engine Light Codes P0300 & P0301

**Ichabod1960** · 12-31-2007, 09:39 AM

I'm in the St. Louis area visiting family and friends and until last night my LJ was running fine. When I went to start up the Jeep last night the check engine light went on and it ran a little rough for a minute or so.

I just got back inside from getting the code and the codes are P 0300 and P 0301. How serious are these codes and what should I do to reset the check engine light?

Thanks,

Nonya · 12-31-2007, 09:45 AM

That code means the cylinders have random misfires,could be so many different causes.From 02 sensors to sopark plugs or even bad gas.Is is running bad?If you have to drive a long distance i would let a dealer take a quick look at it.Don't bother resetting the check engine light,it will just come back on.

robncar · 12-31-2007, 10:02 AM

The P0300, as stated above, is a "Multiple Cylinder Misfire"
The P0301 is a "Cylinder No. 1 Misfire"

I suppose you could perform a visual inspection, pull plug number one and take a look, or just let a dealer take a quick peek.

Listed as possible causes:

INTERMITTENT MISFIRE
VISUAL INSPECTION
(F142), (K334) ASD RELAY OUPUT CIRCUIT
ENGINE MECHANICAL PROBLEM
IGNITION COIL
COIL CONTROL CIRCUIT
SPARK PLUG
CHECKING FUEL PRESSURE
FUEL PUMP INLET STRAINER PLUGGED
RESTRICTED FUEL SUPPLY LINE
FUEL PUMP MODULE
CHECKING FUEL LEAK DOWN
FUEL INJECTOR
INJECTOR CONTROL CIRCUIT
PCM

**Ichabod1960** · 12-31-2007, 10:03 AM

Once the engine warms up, it runs fine. I'll get a hiccup or two right as I start out, usually shifting from 1st into 2nd and then the Jeep runs fine.

I just need to run around St. Louis today about 50 miles but tomorrow I need to drive about 100 miles to my parents house. I can get the Jeep to the dealer on Wednesday before I drive the 800 miles to SC on Thursday or Friday.

buellwinkle · 12-31-2007, 11:53 AM

Consider it a warning that can turn ugly on a moments notice. Random misfires could mean you have a weak fuel pump, fpr, filer getting clogged, clogged injectors, possibly a vacuum leak, bad coilpack. It could be as simple as bad gas so you can reset the codes, refill with a good gas and see if it comes back.

**Ichabod1960** · 01-01-2008, 12:56 AM

Right now, I'm leaning toward the bad gas theory. The CEL has gone out and the engine has run fine all day today. I do have an appointment with a dealer on Wednesday and we'll see what he has to say.

Thanks for everyone's advice and help.