Thanks guys. Gas (premium non ethanol) is about 4 months old. I went out and pulled the codes. No codes, or any pending codes. Whatever it is, it isnt setting of a code. I am leaning towards a stuck injector. Will check coil packs. Based on the shop manual it seems that a bad coil pack would throw a code specific to the cylinder. If nothing else, hopefully I can narrow it down to which cylinder isnt at the party.
I have never really worked on this engine. Just basic stuff. I am thinking of removing the engine covers and pulling the connectors to each injector while running and try and see if that gives any info.
On the OBDII cars, there are two misfire detection systems. One monitors coil voltage and the other monitors crankshaft RPM (it looks for rapid speed fluctuations caused by a misfire). The coil monitoring system will not set an error code if it detects voltage when the coil is supposed to fire; but, if you have contamination on the nose of the coil or the spark plug insulator it is possible for the high voltage generated by the coil to externally flash directly to ground rather than through the sparkplug electrodes. However, this should cause a cylinder misfire which should be detected by the crank RPM monitoring system.
If you have a problem with external flashover of the nose of the coils it should be apparent. You will see black tracking marks on the coil nose and around the boot. Sometimes this can be cleaned off if the tracking is just in the surface contamination; but, serious tracking usually means a new set of coils. Removing the coils covers and pulling the coils is not to hard and an easy way to rule out a coil problem.
A complete cylinder misfire, whatever the cause, should trigger the crank RPM misfire detection system. It is possible that you have what I would characterize as a weak cylinder which is causing roughness in operation; but, not enough roughness to trigger the misfire detection system. That roughness could be related to fuel delivery which might be a partially clogged injector or a sticking injector (slow to open) which is reducing fuel delivery to the cylinder. That problem should cause a fuel mix error; however, if it is only affecting one cylinder then the mixture error may not be enough to trigger a mixture error code. If you have an OBDII code reader that can read the fuel trims, check your fuel trims to see if one of them is really high. That 'could' be a sign of a clogged injector and the ECU trying to correct for that.
If you have an OBDII reader that can read fuel trims, start by checking for high trim values. If you have some high trim values then consider removing your injectors and have them sent out to be cleaned. Checking fuel pressure would be good; but, that typically affects all cylinders, not just one. If you don't have a code reader or the fuel trim values look normal, then remove and inspect the coils. If the coils appear OK then I would consider sending the injectors out for cleaning. If it is not the coils or dirty injectors, things are going to be more complicated.
As a final two shots. If the car has not been started for a few months, to follow up on goldNSX's comment, how old is the gasoline in the car. Skanky gasoline can definitely cause operational problems. To follow up on Jerry@Mobile's comment there is a problem with counterfeit Denso and NGK plugs. If your plugs did not come from a reputable supplier you may have some counterfeit plugs. The plugs don't die instantly, they just wear out really fast because the counterfeiters don't use iridium or palladium in the electrode tips.
