Herky-jerky hot/cold starts 2003 Prius. Missing? CEL

[orange4boy]

It had to happen sometime. Engine light on. No away to get code. Still running though.

The Pri has been missing sometimes when cold and when restarting from hot. The missing dissapears when you get on the throttle and once you drive a short way. The CEL finally came on after a couple of months of this. ( I know, shoulda checked it earlier )

I pulled the sparkplugs (NGK iridium) and found one boot with signs of jumping. Re-gapped to .044" and put her back together with some vaseline. Cured it for a spell. Didn't have access to Dielectric grease. Now its back again and the CEL lit up yesterday.

My guessses so far:
Bad/dying coil
High resistance sparkplug
Old boot still allowing jumping

looks like I'm in the market for one of those home brew code readers.

[orange4boy]

Some more info:

Still getting good mileage.
Have a set of Autolite XP Iridium plugs I could (probably will ) swap with the NGK's
No way to check the resistance.
going out for dielectric grease today.

Another possibility: sticky / dirty injector.