Intermittent Ignition Misfire
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Teching In
Joined: Mar 2011
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Intermittent Ignition Misfire I have a 94 z28. When there is a load on the motor i intermittently get a severe ignition misfire. But sometimes it drives just fine. I was told to change the opti but before i spend 500 bucks i want to know if its really the optispark. The car starts and drives perfectly, but sometimes i drive it and get a pretty bad misfire and it shakes the car pretty hard. any suggestions?
One thing you might look at first is to make sure you're not intermittently losing fuel pressure. A 94 will throw an SES light with misfires, but won't tell you which cylinder. 96 & 97 will. First look at the fuel pressure- plug a fuel pressure gauge into the back of the fuel rail at the schrader valve, tape it to the windshield and drive it in a safe area until it acts up. See if you have a big drop in fuel pressure. Your fuel pump might me going out, you may have a dirty/ partially clogged fuel filter, etc.
Coil, you can do a continuity test but it'll really only show you an open in the winding/ outright failure, or resistance way higher than spec:
http://shbox.com/1/coil_testing.jpg
Worn cap & rotor would probably give you consistent bad performance, fuel mileage would be a bit low. Could also be ICM- heat soak. Have a look here for a good tip:
http://shbox.com/1/4th_gen_tech2.html#ICM_cooling
http://www.shbox.com - bible for LT1 owners
http://shbox.com/1/coil_testing.jpg
Worn cap & rotor would probably give you consistent bad performance, fuel mileage would be a bit low. Could also be ICM- heat soak. Have a look here for a good tip:
http://shbox.com/1/4th_gen_tech2.html#ICM_cooling
http://www.shbox.com - bible for LT1 owners
