sorry for the semiredundant post, i'm at my wits end. there seem to be a lot of posts on misfiring. i've checked most everything suggested.

i was having idle problems. it idles now, but badly, and i'm now getting a code 304 just about every time i drive. the check engine light will start flashing (misfire) and then it stays on. datalogger reads 304. ALWAYS cylinder 4. the plug in that cylinder looked totally totally frosty white. we switched it with the plug from cylinder 1, and tried again. 304 AGAIN. we checked out the distributor, it looked brand spanking new. damned clean, really. i checked all the connections to the EMS and the ECU and VAFC. all good. checked all the wires to the injectors. all good. moved the ground from the a/f gauge and the ground from the EMS away from the ECU grounds. checked resistance of the plug wires. normal (increasing consistently with longer length).

finally, we stuck a probe onto the injector while running, and while my buddy who is a tech at honda in oakland couldn't hear it, i could distinctly hear, under the sound of rushing fuel, a very consistent "click click click click click." just to verify, we pulled the plug on the injector while it was idling, and sure enough it got pissed off. so the injector is definitely firing. it may be clogged or something, i guess.

the car does not smoke, it seems to drive OK off idle, and it pulls quite hard (DAMN hard, actually, but i have been very hesitant to floor it given the situation).

my vacuum gauge does not read quite what it used to (16-18 instead of 19-21) but we could not find a leak using the "cigarette lighter" method.

what now? what else could affect just one cylinder in this way, and only at low RPMs from what i can tell. clogged injector? tight or bent valves? manifold leak?

 

I'd start with a compression check and go from there.