ANC297

iTrader: (2)

I noticed a slight mis-fire a couple of weeks ago, just a quick shudder upon idling every couple seconds...Its subtle enough not to throw any codes, but something is going on.

Today, it got much worse. The vibrations are more intense and more frequent...

Where should I start?
-Seafoamed maybe 3k miles ago.
-New NGK Iridiums about 7-8k miles ago.

Could a coil pack be "on the way out", or is it a working or not working kinda deal?

01tl4tl

coil packs often fail slowly and as you describe
may not throw a CEL,, but stop by the parts store for a free code scan
if its multi cyl misfire, buy 1 coil

this is assuming you already checked all the wire connections to the coils

if one got dropped or mishandled during plug change- this would be right on schedule for its failure

01tl4tl

ch vac line used for seafoam is on firmly and hose clamp in place

01tl4tl

you could also have clogged egr ports- how many miles,
and have you done that already?
about 75kmiles and they clog up
remove intake manifold-
carb cleaner and wire coat hanger + 1.5 hours of your labor fixes that for another 75kmiles
clean TB air plate and IACV while its apart

01tl4tl

first time seafoamers should repeat after a month/1500-2000 miles
then good for a year

ANC297

iTrader: (2)

EGR is clear...As are the wire connections.

So you think its a coil otw out?

ANC297

iTrader: (2)

Also, my purge valve is ticking away...Could this have anything to do with the misfire?

01tl4tl

get the codes scanned at parts store- see if a coil misfire codes is showing yet

ANC297

iTrader: (2)

No codes.

rcb2000

yes because your issue is a vaccum leak not a spark issue BTW

ANC297

iTrader: (2)

So you think the purge valve solenoid is causing a vac leak, and once replaced the misfire will disappear?

rcb2000

no once you find the vaccum leak in the purge valve system them you'll find the issue maybe replace the front motor mount?

ANC297

iTrader: (2)

The front mount is only 3 months old, give or take.

01tl4tl

so ck it and its vac line anyway
brand new parts are subject to failure too~

maybe rear mount has failed now

VTEC11

Since the problem is getting worse sounds like a coil going bad. Is it misfiring consistently at idle? If so letting the car idle for 20-25 minutes might bring up a CEL and a code. Mine was doing the same thing last week after I changed spark plugs. I thought I got a bad plug because the engine was missing/jerking every few seconds at idle but revved to redline 100% fine. NO CEL or no codes for a week, again because the car was running fine except at idle. I left it on one morning to warm it up (for an extended time ~20 mins.) and when I got in got a code 304. Changed coil 4 and the idle was perfect again.

VTEC11

I must have damaged the coil slightly somehow while changing the plugs because I know I replaced coil 4 a couple of years ago. So listen to what 01tl4tl says about handling the coils, haha.