2003 p0300 p0301 p0302 p0303 p0304
 

Hi yall!

2003 CIVIC EX 1.7 auto D17A2 125k miles -- Intermittently get these codes. The engine runs rough & sputters with the Engine light on.

After clearing the codes the engine runs good with an occasional misfire at idle (that lasts for like a 1/10 second).
The error comes back when the car is started up cold in the AM. Clear the codes and it drives fine!

I checked -all plugs look great! this car barely goes 4k miles a year. Drives 5 mins twice a day -not every day!
** I havent replaced my faulty Coolant Temperature Sensor yet. Its stuck on. Is this causing the problem??

yea, I loose a little coolant each week, but its never overheated and has been like this a long time! Head gasket will be done soon!

so I dont waist time what should I be looking for first??

thanks!!!

Re: 2003 p0300 p0301 p0302 p0303 p0304
 

Only 5 minutes per run? What do the plugs look like?

I might suspect it's 'loaded up' and needs run hard and fast on a highway to burn the carbon out of the plugs.

Only 5 minutes run time does not get the plugs up to ideal operating temperatures, their "self cleaning" temperature.
This is what happens to new and used cars on the lot, they get started and moved every week and most never get driven, they load up and either run like crap or just flood out and won't start.



Check the oil and coolant first, warm it up and take it out for a hard run, and then see how it starts tomorrow?

By hard run, I think of wide open acceleration runs, say start at 10 mph (so you don't roast the tires LOL) then mash the gas pedal and keep it there til you hit highway speed.
Do it a few times.
Let it shift at redline.

Be safe about it though. Don't break laws. Don't do it in a school zone. Etc.

This gets the spark plugs good and hot, they have to get hot in order to burn out accumulated soot deposits and turn the porcelain white again.
And some steady 65-70MPH. Maybe 10-15 minutes.

Hell, maybe a simple cruise on the highway at 70 for an hour would do just as good for it.

Re: 2003 p0300 p0301 p0302 p0303 p0304
 

-all plugs look great! NGK's

I took it on the highway the other day after clearing the codes and all was good till morning when i started it up.

today the car sat for a few hrs in the afternoon and the codes were there when I started it up. Its almost like it generates the codes in its sleep!

cleared the codes and all is well.

hopefully ill have a new coolant sensor tomorrow

Re: 2003 p0300 p0301 p0302 p0303 p0304
 

Valve adjustment? Tight valves might do this.

Re: 2003 p0300 p0301 p0302 p0303 p0304
 

nothing was done to the car other than an alternator a month ago.

do valves get tight on their own? I never heard of this.

I think this all started because of the 90deg weather??

but how do I get rid of it?

Re: 2003 p0300 p0301 p0302 p0303 p0304
 

Yes they can and do.

Will it cause your problem? Could be.
Hondas don't use hydraulic lash adjusters like most other manufacturers' engines. They must be adjusted manually.

Valve clearance inspection and adjustment is a periodic routine maintenance.

Re: 2003 p0300 p0301 p0302 p0303 p0304
 

this morning I started the car with the EGR wire unplugged and the code did not appear!

the idle was rough but no code. the idle got better as the car warmed up.

no engine light at all.

what do you recommend here.

thanks!

Re: 2003 p0300 p0301 p0302 p0303 p0304
 

There's a lot of 'maybes' going on. Maaaaybe it just wasn't rough enough to set a code? Didn't last long enough to set? IDK. You say it was still rough idling so....

The EGR isn't supposed to be activated when the engine is cold, nor should it be activated at idle, so unplugging it shouldn't have had any effect on how it ran at that time.

Is the EGR valve leaking? (pintle stuck slightly open) Maybe...?

If you think it may be, You could remove the valve and block it off (seal the passage with a thin cardboard gasket), bolt the valve on to cinch the cardboard in place, and see if the rough idle clears up.

Re: 2003 p0300 p0301 p0302 p0303 p0304
 

among other things, I wanted to change the fuel filter. is there only 1 fuel filter? and its located in the gas tank? or is there another fuel filter to replace?

thanks

Re: 2003 p0300 p0301 p0302 p0303 p0304
 

Fuel filter is in the top half of the pump module (tank unit).

Check aftermarket, Honda wants to sell the pump and everything as one big piece.

Re: 2003 p0300 p0301 p0302 p0303 p0304
 

giving this misfire engine code problem a lot of thought, I forced myself to not go any further without changing my "looked good" spark plugs for new ones.

so with 4 new Denso Plat TT's -my car (so far) is running smooth & engine code free!

I still want to change the fuel filter but i have to find out how to check the fuel pressure first!

Thanks again for your help!