1994 will crank and sometimes start
09-14-2018, 12:03 PM
#1
Advanced
Thread Starter
1994 will crank and sometimes start
I have this issue where the car will sometimes start but other times will crank and not run. No diag codes. Can the VATS allow the car to crank but not start or will it not even allow the car to crank ? The engine has about 100Kmiles on it and the ICM has been replaced. I want to rule out VATS before I start doing tests on the Opti and coil. Thanks!!!
09-19-2018, 12:47 PM
#3
Advanced
Thread Starter
1994 Corvette LT1 sometimes starts ......
When cranking to start it, tach will sometimes show about 500rpm, other times nothing or needle moves negative.
It will sometimes start and run fine for about 10 minutes then start to develop a rough idle, misfire intermittantly and then stall.
Right after that sequence it will not restart. You have to let it sit for hours.
Previous owner installed a new ICM but I am wondering if he put thermal grease where it needs to be, and if not, that maybe the ICM
gets too hot after 10 minutes. Anyone know how to test the ICM while car is running ???
Reason I am not ready to suspect the Optispark just yet is that the engine will run nicely for about 10 minutes or so, until it heats up...
Other factors.... the car has a bad battery that will not hold a charge very long .... I don't think that can cause the running issue....
Coil has not been changed, it there a way to test that ?
Any suggestions ??
Thanks....
09-20-2018, 11:03 AM
#4
Race Director
More details on the issue with this LT1.
When cranking to start it, tach will sometimes show about 500rpm, other times nothing or needle moves negative.
It will sometimes start and run fine for about 10 minutes then start to develop a rough idle, misfire intermittantly and then stall.
Right after that sequence it will not restart. You have to let it sit for hours.
Previous owner installed a new ICM but I am wondering if he put thermal grease where it needs to be, and if not, that maybe the ICM
gets too hot after 10 minutes. Anyone know how to test the ICM while car is running ???
Reason I am not ready to suspect the Optispark just yet is that the engine will run nicely for about 10 minutes or so, until it heats up...
Other factors.... the car has a bad battery that will not hold a charge very long .... I don't think that can cause the running issue....
Coil has not been changed, it there a way to test that ?
Any suggestions ??
Thanks....
When cranking to start it, tach will sometimes show about 500rpm, other times nothing or needle moves negative.
It will sometimes start and run fine for about 10 minutes then start to develop a rough idle, misfire intermittantly and then stall.
Right after that sequence it will not restart. You have to let it sit for hours.
Previous owner installed a new ICM but I am wondering if he put thermal grease where it needs to be, and if not, that maybe the ICM
gets too hot after 10 minutes. Anyone know how to test the ICM while car is running ???
Reason I am not ready to suspect the Optispark just yet is that the engine will run nicely for about 10 minutes or so, until it heats up...
Other factors.... the car has a bad battery that will not hold a charge very long .... I don't think that can cause the running issue....
Coil has not been changed, it there a way to test that ?
Any suggestions ??
Thanks....
09-23-2018, 10:41 AM
#5
Le Mans Master
Having read all the info above, this would be the time to check for codes to see if there are any for the opti.
Codes are not the final word for anything and in this case if you lose the low or high resolution pulse it will set a code. But if both pulses are lost no code is set. Codes and selftest is not a perfect world.
Codes are not the final word for anything and in this case if you lose the low or high resolution pulse it will set a code. But if both pulses are lost no code is set. Codes and selftest is not a perfect world.