Recently my car has developed a stumbling miss that starts almost immediately after the engine reaches operating temperature, and gets worse the longer it runs. It runs fine while cold, but runs like the timing might be retarded a bit. After it warms up it has a random stumbling miss. There are periods of 5 seconds sometimes where it won't miss at all, other times it misses every rotation. If it were the optispark, wires, or plugs, I would expect the miss to be more repetitive.

I am trying to figure out whether its ignition or fuel related and go from there. No SES Light and No Codes were ever thrown. I ran Seafoam through the top end (brake booster vacuum hose), which didnt make much difference, other than filling a 50ft radius with smoke. I plan to add some to the gas, and possibly have the injectors professionally cleaned via the schrader valve. Anyone know of a cheap professional cleaning kit that connects to the schrader valve?

The coil was just replaced, the plugs were replaced less than 3,000 miles ago with NGK TR55's, the Opti and wires were replaced less than 30,000 miles ago.

 

Well, I had the same problem. Sooner or later it will get alot worse. My problem was the opti. I changed my plugs, wires and coil first, that didn't help. So I changed the opti and all the problems went away!

 

I was hoping it wouldnt come to that... I don't really have the ~$300 or the time to do it myself right now. I think I'll have a diagnostic run on it first, or buy the cable and do it myself, before I give in and replace the opti. The Ignition Control Module has never been replaced, I wonder if it could cause problems like this?

 

If it is the opti, the problem will just get worse to the point were you can not drive the car. It will reach a point while your are driving and the car will just die.

 

Well it's been like this for a couple weeks, and hasn't really seemed to get any worse, it's about the same. It starts right up and runs strong while cold, but it goes to hell once its warm. This doesen't really sound like the opti to me.
If a professional fuel injection cleaning and a diagnostic don't shed some light, i'll consider the opti.