Mannymuaythai

Hello, I have a 2001 Honda Civic LX that just started misfiring yesterday and I could use some help.

So I was driving yesterday getting on the freeway and trying to get up to 60mph, at about 58 in 5th gear my car jerked and lost a good amount of power, followed by a flashing CEL.
I went straight to Oreilly to plug it in and get DTC codes and got:
P0300 Multiple Misfire
P0303 & P0304 Misfire of cylinders 3 & 4

I limped it home shuddering the whole way and hopped on the forums, after a good amount of research it looks like it is common for the EGR ports in the intake manifold to clog and cause misfires and since it is the 2 cylinders closest to the EGR Valve it seemed to make some sense. Problem is the 2001 LX has no EGR valve but the 2001-2003 EX does and everything above that all come with an EGR (apparently). I looked into this after trying to unplug my EGR and see if that would fix it only to find there was nothing there.

SO does anyone know if it is a universal intake manifold Honda uses on the EX and LX (EGR and non EGR models). If so I will get to taking it apart and cleaning out the gunked ports. If not does anyone have any ideas as to where to turn?
I don't imagine 2 injectors, spark plug coils, or spark plugs would go out at the same time, just doesnt really make a lot of sense. At first I thought maybe it slipped a tooth on the timing, but it looks like clogged EGR ports is the most likely.
Spark plugs have been replaced with OE plugs recently so I ruled that out also. Also have run seafoam through the gas and let it idle for about 10 minutes to see if that would break down any gunk but so far nothing.
Please help!

Former User

Were the plugs properly gapped?

Mannymuaythai

Yes, absolutely.

I changed my PCV valve and it was very gunked up, it was not working as it was supposed to, so I thought that might fix it but no luck. It helped a little though, its definitely not running like there are multiple misfires, it runs as it normally would above 3000 rpm, but under is pretty shaky and rough, but not 2 misfiring cylinders rough, I would expect my car not even start w/ 2 misfiring cylinders.. Anyways, also ran seafoam through the gas tank and drove it around for about 20 miles... Between changing out the PCV and running the seafoam through the gas it definitely made a difference and was running better than yesterday. Still flashing CEL, but only below 3000rpm after that it turns solid.

I took it back to oreilly and ran a diagnostic check again to see if anything had changed and I did get a new misfire code P0302 for the #2 cylinder. So that makes 2, 3 and 4 now. But there is no way it could be plugs or injectors or anything specific to a cylinder its gotta be something before or after clogging it up in my opinion....PLEASE HELP
DOES ANYONE KNOW IF THE INTAKE MANIFOLDS ARE UNIVERSAL FOR ALL MODEL CIVICS, MAINLY BETWEEN THE LX (MY CAR ) AND EX (EGR MODEL CARS)
Thanks to all in advance who can lend some advice, I really appreciate it.

It might also help to note that the lack of power I was experiencing was exacerbated after I welded the cracks in my exhaust manifold. Since I did that, when shifting into 2nd gear it loses quite a bit of power and momentum ( falls on its face) and it felt like I had a general lack of power than before I welded the manifold ( which I expected to be the opposite).

Mannymuaythai

No update today, still hoping someone can answer this for me. Called the Honda dealership parts dept. and they were unsure. trying to avoid pulling the intake manifold if there are no egr ports on non egr models.
My next guess would be oxygen sensor.

NDNV

Random misfire only at low RPM and under load: check fuel pressure, low compression, low quality of fuel, correct EGR valve function (if applicable to your model year?).
Check fuel injectors, ignition coils (at idle, disconnect each one separate and the one that does NOT change the idle is bad), check connections at ignition coils and injectors, check spark plugs, open or shorts in wires from coil and fuse or coil and ground and PCM to coil, compression in the cylinders.

Did you use a different brand of gas or station lately? Sure sounds like symptoms of bad gas (BURP!)

Mannymuaythai

It is not misfiring under load. The flashing CEL and the shaking stop once I get above 3000.
It really feels like there is an air restriction, possibly a fuel restriction but I think air because once I replaced the PCV it ran a little smoother, plus there was a ton of gunk on the PCV which leads me to believe there is likely a ton of gunk somewhere else. I am thinking the EGR ports, but still waiting on a Honda tech or someone who knows better to tell me if models without EGR have the ports or not, I would imagine they made a universal intake manifold for all 2001-2003 Honda civics. If I dont hear from anyone today I am going to just remove it anyways and hope I find EGR ports that are severely gunked up. Otherwise I am turning to Fuel pressure regulator and O2 sensors.

Rick hybrid

try cleaning the idle control valve.
switch the coil packs.
if you don't have the egr valve , why would would there be gunk in egr ports.
buy a can of carb cleaner spray and spray it down the intake while a friend works the throttle.

Mannymuaythai

Update:
Finally got an answer to my question. Called my local Honda dealership and checked with parts dept. to find out if there were different part #'s for the ex and lx intake manifolds, turns out the intake manifolds are universal for all model civics in this year at least. Also its not the manifold, but the spacer between the manifold and the head that has the EGR ports.

So I got to pulling apart the intake system to see if there was clogging and turns out it was not as clogged as I thought. I cleaned out what gunk there was in the manifold, spacer, egr ports, throttle body, injectors and head with some gas and my toothbrush (now I need a toothbrush). I also took off the PCV housing and cleaned the inside of that with some carb cleaner. Haven't finished putting it all back together, but it should be done tomorrow early afternoon and I will update again.

Mannymuaythai

Motor is blown, pulled the plugs and there is gobs of burnt oil all over the plugs.. Anyone know a cheap way to rebuild or replace motor in Seattle area?