LT1 hard miss - ideas??
Thread Starter
Intermediate
Joined: Mar 2007
Posts: 31
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LT1 hard miss - ideas??
My 1993 LT1 6 speed has been experiencing a "hard" miss after operating for several hours. On Saturday I drove for over 3 hours with no issues, then all the sudden the car starting missing hard until it was almost undrivable. After the car sat overnight it drove perfectly for the hour drive back to my shop. Today I checked the coil & coil module wiring connections, checked for anything obvious, and drove the car about 1-1/2 hours and it starting missing again. Seems like ignition issues, maybe Opti-Spark. Any ideas? Thanks!
Some details:
Some details:
Thread Starter
Intermediate
Joined: Mar 2007
Posts: 31
Likes: 0
I replaced the ICM about 2 years ago. Not to say it might not be the issue, but it is recent.
The fact that it runs great cold or even hot for the first several hours and then starts missing is baffling. If you "listen" to the miss at the exhaust it appears to come from the pass side only.
Still wondering if it is the Opti-Spark. Maybe one spark plug button in the cap gets too much space or allows a miss after it heats up.
Thanks for the suggestion.
The fact that it runs great cold or even hot for the first several hours and then starts missing is baffling. If you "listen" to the miss at the exhaust it appears to come from the pass side only.
Still wondering if it is the Opti-Spark. Maybe one spark plug button in the cap gets too much space or allows a miss after it heats up.
Thanks for the suggestion.
Safety Car
Joined: Sep 2010
Posts: 3,752
Likes: 190
From: Indiana PA
Can you replicate this once it starts under ALL engine operating RPM's? Does it do it at idle?
Sounds similar to a fuel injector issue I had on my 93. The Multec 1's are known to be crap.
Just FYI I found it with an occilliscope. The injector OHM test, while not terrible is not that great. Something you could try when the car is hot and starts to miss and then do the test while everything is hot.
Testing the ignition system hot for spark isn't a bad idea either. Again access to a scope would make this TONS easier and WAY more accurate.
A lot of info I put other there on these cars.
https://www.youtube.com/playlist?lis...fOSbxBy4ciZrDv
Sounds similar to a fuel injector issue I had on my 93. The Multec 1's are known to be crap.
Just FYI I found it with an occilliscope. The injector OHM test, while not terrible is not that great. Something you could try when the car is hot and starts to miss and then do the test while everything is hot.
Testing the ignition system hot for spark isn't a bad idea either. Again access to a scope would make this TONS easier and WAY more accurate.
A lot of info I put other there on these cars.
https://www.youtube.com/playlist?lis...fOSbxBy4ciZrDv
Thread Starter
Intermediate
Joined: Mar 2007
Posts: 31
Likes: 0
Hi Rubie.
Does it at idle and at all rpms.
I ohmed all the fuel injectors and they were between 13-14 ohms.
I have a friend at a shop. May be able to get it scoped.
I assume your issue was a bad fuel injector(s). Curious if it is a FI why it runs OK for several hours, not just until fully hot.
Thanks for the advice.
Does it at idle and at all rpms.
I ohmed all the fuel injectors and they were between 13-14 ohms.
I have a friend at a shop. May be able to get it scoped.
I assume your issue was a bad fuel injector(s). Curious if it is a FI why it runs OK for several hours, not just until fully hot.
Thanks for the advice.
Safety Car
Joined: Sep 2010
Posts: 3,752
Likes: 190
From: Indiana PA
Hi Rubie.
Does it at idle and at all rpms.
I ohmed all the fuel injectors and they were between 13-14 ohms.
I have a friend at a shop. May be able to get it scoped.
I assume your issue was a bad fuel injector(s). Curious if it is a FI why it runs OK for several hours, not just until fully hot.
Thanks for the advice.
Does it at idle and at all rpms.
I ohmed all the fuel injectors and they were between 13-14 ohms.
I have a friend at a shop. May be able to get it scoped.
I assume your issue was a bad fuel injector(s). Curious if it is a FI why it runs OK for several hours, not just until fully hot.
Thanks for the advice.
If your having an ignition system issue hot the scope patterns on the secondary (plug wires) side and primary (coil and Opti-Spark) will show up.
Count your blessings its doing it at idle and constantly once hot. Just a matter of hunting it down.
