I have a 95 Z w/ a 4L60E and it has 113,000 miles on it. It is pretty much stock. About a month and a half ago I was driving in the rain and my car began to misfire. The problem has been occuring ever since. The misfire is not noticeable until the car warms up, and it stumbles right before shifting gears. I was also running down the interstate at 75 w/ cruise control on and I noticed the misfire as well. The opti has 113,000 on the original. I have already replaced the coil, plugs, and wires. Does anyone know if there is a test that I can run on my ICM before I replace the opti? I would like to rule that out. What other parts could be the problem? Any suggestions on this problem before I change the opti? Also, I know it would be a good idea to change the water pump when changing the opti, but I dont have the money right now. My water pump was changed about 50,000 miles ago. i was wondering what is the best way to seal it when i put it back on. Should I use RTV Sealant and if so which one? How many miles do w/p usually get? Should I apply sealant to both sides of the gaskets or only on oneside? Thanks

 

Once you remove the Opti and open it up, in most cases you can see what is wrong. If the optical module is bad, you'll get a high or low resolution pulse DTC.

WD

 

Being that its the original opti, I'd say its probably done for. There is an opti and spark test that you can perform:
http://shbox.com/1/4th_gen_tech2.html#opti_test
But I wouldn't let it totally rule out your opti. I did the test once, and my opti was still bad (one of the plastic rivets on the rotor broke).
You're pump may be fine, but 50k is not nothing. I think as long as you clean the mating surfaces very well, all you'll need for a tight seal is new water pump gaskets.