Service Engine Soon light

[jcs44]

I have a 96 LT4 (36K miles) on which I have recently had replaced the water pump, opti-spark cap and rotor, and spark plugs. Most of the time it runs fine, but about once a week the Service Engine Soon light comes on, flashing at first and then stays on steady, and I think I can feel it missing some. Within a day or so the light goes off and all is well until the next time. I've been back to the shop twice and no codes have been set. We're thinking an intermittant sensor somewhere.
Any ideas on what this might be?

Thanks, JCS44
96 LT4 Vert, triple black

[David-F]

Your 96 is OBDII system so a flashing light is an indication of a possible cat. converter damange event so the PCM will flash the light, most likely set if it detected an engine miss fire, but it should have set a P0300(ramdon miss fire), then when the miss fire stopped light would come on steady untill the ign. is turned off. What was used to check for codes? The PCM should have stored the code and also history miss fire so you should have a place to start.

David Fulcher

[jcs44]

Local Corvette specialty shop supposedly has latest and greatest code reader/scanner, but I don't know the specific model. If you can tell me, I'll check. Light is on for a while and then off for a while. Usually on in the morning and off that afternnon or next day. Recently replaced water pump, distr cap & rotor, and plugs.

Thanks, JCS44

[Notorious]

Originally Posted by David-F

Your 96 is OBDII system so a flashing light is an indication of a possible cat. converter damange event so the PCM will flash the light, most likely set if it detected an engine miss fire, but it should have set a P0300(ramdon miss fire), then when the miss fire stopped light would come on steady untill the ign. is turned off. What was used to check for codes? The PCM should have stored the code and also history miss fire so you should have a place to start.

David Fulcher

Agreed. I have trouble believing that the SES light could be illuminated while an obvious problem was occuring w/o logging a code. However, how long after these occurences have you had it checked for codes? How many miles and on/off cycles? The next time have it checked ASAP after the symtoms occur.