Yuen001

taking off the intake manifold is gonna be a serious pain. why would it not throw a code for insufficient egr flow if the holes are clogged ?

postman

because the egr is functioning correctly. that code will only trigger when the egr is malfunctioning 99% of the time, my suggestion would be to try and seafoam the engine

Yuen001

i was thinking about seafoaming the car. i'll give it a shot.

Nick Z32

hey i am having the same situation... did the seafoam work?

pm me plz ... if you fix your car

brasstop

I had this same exact problem and identified the root cause and solved the issue. I have a 2003 Civic EX 4 door with 250K miles on it. The problem started just after a timing belt and water pump change.

Symptoms are random multiple misfires under light throttle when the engine is warm. The engine idles perfectly and performs under load conditions and moderate to heavy acceleration. I got the same DTC codes P0301, 0302, 0303, 0304. I started by believing the dealer that this was a coil issue since I had burned a set of coils around 160K. After that didn't work, the dealer wanted to throw injectors on the car for another $600. I didn't buy that so I started doing the homework.

The EGR valve operation is the give-away with these symptoms. The valve opens when the engine is up to temperature so that it can recirculate exhaust gas through the combustion cycle, but only under light throttle conditions and above idle RPM. The valve closes again under heavier load conditions or if the RPM is above about 3000. Because of this I tested the theory by unplugging the connector to the EGR then drove the car around and found the problem went away so I concluded that the cause of the symptoms I was seeing is one or more blocked or restricted EGR ports.

The dealer said I was nuts because they aren't seeing an EGR related code. They wanted to throw parts at the fuel delivery system.
Here's a quick way to see if you have the same problem. Unplug your EGR valve's connector and go drive your car around. If the problem goes away, you have plugged EGR ports.

The reasons are simple. The EGR sensors are looking for flow and actuation of the valve. So if the valve opens and the proper flow is measured, you won't get a code. When you plug or restrict an EGR cylinder port, the flow redirects to the other cylinders and leans out your mix and you get a misfire. The misfire codes register on the cylinders with UNRESTRICTED flow as well as with restricted flow if the fuel air mix is off enough to cause a misfire. Only after you've plugged more than two ports at once will you affect the flow and if it is an intermittent blockage like a loose piece of carbon or something, the flow restriction code will likely never register.

The fix is to clean the EGR passages. On a 2003, that entails removing the intake mainfold so be prepared for about a $400 bill from a repair shop or a day in your own shop.
Your dealer or auto care provider may not believe you at first, but be persistent and insist on them performing a cleaning of the EGR passages.

fl1p_m0nk

did you end up finding/fixing the problem? is so, what was it?

cockerstar

I have been having a very similar issue with my 2003 Civic EX coupe with 230k miles. I've been chasing a misfire that predominately shows on 3/4 and occasionally on 2. After following every step in the P030x troubleshooting section of the FSM I was empty handed!

I unplugged the EGR, cleared the codes, and the missfire hasn't been back!
I'm planning on pulling the intake and cleaning the EGR passages to see if that alleviates the problem.

brasstop

Make sure when you clean the ports that you also remove the EGR valve itself and clean as much of that as possible as well. Then be meticulous in removing all the loose carbon. Any left overs can clog ports and cause the problem to persist. If you have idle problems after cleaning them, pull the EGR valve as there might be a piece of carbon caught that is not letting it properly close.

gorbashreduk

It's called a crank-shaft position sensor and cam shaft sensor. I fought this problem for two years before I figured it out. All kinds of funny things will happen to your car, all of which seems random. When its hot your car might not have power, may die randomly, and several other possibilities. Dealer had no idea what was wrong with my car (2001 Honda Civic LX), but told me they could fix it for $2800. I couldn't afford that, hence began my torture run.

The nice thing is this is like a twenty to thirty dollar fix. Crank-shaft position sensor sold pretty much anywhere. Bad thing is if you don't figure it out other problems will follow. O2 sensor ($40-$100) will go out no matter how often you replace them. Engine will likely overheat causing the catalytic converter to crack, ($300-$600). You may or may not get codes. It will seem to vary on the weather. One day your car drives perfectly the next your afraid to go anywhere. Short drives seem to be better the long drives.

I fixed my car finally at the end of my two year torture run. I replace both front and back O2 sensors and replace the catalytic converter with a header ($75), and put in a $32 crank-shaft position sensor and cam shaft sensor. In the end my car preformed amazing. It felt better than it did when I bought it at 29,000 miles. My car now has 220,000 going strong. Problem happened at 155,000 miles. Problem fixed at 200,000 miles.

This sensors are both located on the drivers side under the timing belt housing. One you can get without removing any thing the other one is kind of a pain.

Hope this helps.

fl1p_m0nk

is it possible for the problem to be those two sensors and now trip a code in the scan tool? if so, why?

HilltopsGM

Yuen001 - if you are still around, did you solve the problem?

I recognize this is an OLD thread . . . but did you (or anyone else) ever find a solution to this?

I have a 2002 that is acting in a very similar fashion.
People keep suggesting the egr passages . . . accept I don't have an egr valve.

Random misfires; idles like crap if it doesn't die; no power for acceleration (even when sitting in Neutral).

Drove to work one day - it was fine.
Went to come home, and it ran like crap.

Coil Packs are good, plugs are good, timing was checked (didn't skip a tooth), change the camshaft sensor - (No Help there); compression is good.
Suggestions?