I just swapped a k20a2 into my car two weekends ago. Everything went fine, had the fluctuating idle but that went away in a couple days. It pulled hard and I thought everything was perfect. A day or two after that, it started misfiring. Replaced the plugs with Denso Iridiums and no difference, CEL came on in a couple minutes.
Cylinder #4 (I think it's #4 - it's nearest to the tranny) was completely carbon fouled within 100 miles on the plug. Plug IS sparking. I tried a new plug in that cylinder and it was carbon fouled after a couple minutes of idling. Swapped injectors with a k20a3 injector, still no power. I put the a2 injector back in and gave up - it was 2am.

So it seems to be getting spark and gas but cylinder #4 is running rich. I have a SRI and full exhaust. What could this be? (I can't afford to get it tuned right now)

I'm going to do a compression test but I doubt that cylinder has low compression because the motor was pulling hard for a few hundreds miles.

I did the compression test. Please note that I used a $15 compression tester I just bought from Harbor Freight and this is my first time doing the test alone. I tried letting each cylinder crank 5 times but I can't be certain since I didn't have anyone watching the needle jump.

(Pulleys side) - 165 - 165 - 160 - 160 (tranny side)
I bolded the cylinder that is fouling plugs.

Here is the plug (has about 60 miles on it since I cleaned it last. About 250 total miles on it):

 

weak spark(coil) maybe?

does it misfire in that cyclinder?

 

Well, autozone's crap scanner said it misfires in all the cylinders, Acura said it was only that cylinder (4) and 10 minutes later said it's #1, 2, and 4.

This cylinder is misfiring for sure, but I think it's the only one misfiring. I mean, it still has power, more than the a3 and this is the only plug that looks bad at all. I swapped coils before and it didn't change a thing. :s

 

Any other suggestions?

 

Swap the #4 injector and coil pack to another cylinder.

 

I have. From what I've done it seems like it's not the plugs, coil pack, injectors (or wires), or fuel rail.

: \

 

check the vacuum line to the fpr, see if there if fuel in it..

 

I'll check it out. Thanks a lot.