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Spark knock and slight misfire Spark knock and slight misfire
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Old 09-27-2010, 06:48 pm   #1
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CM Spark knock and slight misfire
Hi all. I'm new to this forum and have a question. I own a 1995 Lt-1 which is stock. Accelerating from low rpm with the engine under a load, (fifth or sith gear) the engine will pre-detonate and misfire slightly. Worse when the a\c is on. What should I check for?
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Mike
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Old 09-27-2010, 06:53 pm   #2
 
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Plugs/wires would be my first stop. Any change to the rocker arms? Sometimes, they can use a good re-torquing.

Is this when cold, when hot, all the time?
1985 Z51 4+3 trans rebuilt 5.7 TPI,(.10 over) w/ CompCams 12-262-4, 52MM Throttlebody, underdrive pulleys, reworked heads, Hypertech Thermomaster chip, & cat back exhaust
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Old 09-27-2010, 06:59 pm   #3
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No change to the rockers. The negine has never been opened up. Currently has 62k on the clock. The knocking and misfire is definetely more noticable when the engine is at normal operating temps.
Mike
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Old 09-27-2010, 09:04 pm   #4
 
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My first place to look would be spark. Sounds like you've got a dead hole.

Check the cap, rotor, coil--all the associated wires too.
1985 Z51 4+3 trans rebuilt 5.7 TPI,(.10 over) w/ CompCams 12-262-4, 52MM Throttlebody, underdrive pulleys, reworked heads, Hypertech Thermomaster chip, & cat back exhaust
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Old 09-28-2010, 08:10 am   #5
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Thanks for the reply. Is there a way to check the opti's performance without dissasembly? What about the coil?
Mike
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Old 09-28-2010, 12:49 pm   #6
 
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I dunno about the Opti. It does have a horrible reputation though.

Have you checked for any codes?
1985 Z51 4+3 trans rebuilt 5.7 TPI,(.10 over) w/ CompCams 12-262-4, 52MM Throttlebody, underdrive pulleys, reworked heads, Hypertech Thermomaster chip, & cat back exhaust
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Old 09-28-2010, 03:38 pm   #7
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No codes at all.......
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Old 09-28-2010, 05:02 pm   #8
 
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Well, it's back to basics then--spark (including the Opti) and rocker arms.

Check your wires well. I've seen some burn through and arc.
1985 Z51 4+3 trans rebuilt 5.7 TPI,(.10 over) w/ CompCams 12-262-4, 52MM Throttlebody, underdrive pulleys, reworked heads, Hypertech Thermomaster chip, & cat back exhaust
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