Random misfires are causing check engine light (according to dealer mechanic). Usually light goes out some time later. Using fuel injector cleaner seems to make the problem less frequent. Replaced the plus and wires. What could be causing this problem? What should I do?

What year? What engine? Has it been scanned while driving looking for odd KR?

Maybe the ICM? I'm guessing.

96 SSEi, 3.8 super charged...

What is KR?

Knock retard. When the air fuel mixture starts burning too early before the spark plug discharges, the cylinder will reach max pressure before top dead center. The knock sensors sense knock, and the PCM will do what it can to stop it from happening again short term (and long term be retarding timing in general.

What was the code that set the light?

Thus a timing problem? I have noticed performance is poor. I thought it was age.

I would have to ask the garage for the codes. My understanding is that there were a number of different codes occuring seemingly randomly.

I can ask for codes info. Would this help?

No your problem is NOT timing


and getting the code number would help.

also if its a misfire a good place to start would be to replace the plugs and wires
(doing them fixed my car up in a hurry)

Yes, the actual codes would help as there are several things that could cause your problem. When does the light start flashing? Normal cruise, wide open throttle, slight acceleration? Fuel pressure, coils, ignition control module, vacuum leaks, and corroded battery cables are some possibilities.

What brand plugs did you use?

What grade of fuel do you normally run? Should be using 91 or higher.

Random or multiple misfires can be caused by
Fuel grade
Pulley size
Spark plug heat range
Loose ground connections
ICM

If you start by looking at your fuel and ensure you are only using premium (highest octane in your area) that'* step 1. Step 2 is ... have you changed anything lately?
Spark plugs fall into the anything lately category. Platinum and or Bosch plugs are known to have issues in our waste spark system that is in our cars. Loose or poor grounds are also a factor that is easily located and remedied. Due to the cost..the last item to usually question is the ICM.

Double check the plug wires to make sure they are routed correctly and not touching the oxygen sensor wiring.