LT1-LT4 Modifications 1993-97 Gen II Small Block V8

96 lt1 misfire. please help

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Old 05-16-2012, 04:07 PM
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Default 96 lt1 misfire. please help

so..i just put on a set of hooker long tubes on my 96 z. while i had the headers off i changed plugs and wires. the car has 75k miles and it was the first tune up. but...i didn't change the distributor so its still the original opti. well the car ran great and i took it to be programmed and it came back with a misfire code. when i got it home and took a look i found out that there was a problem with the fans and they didn't kick on. as well as a burnt wire. so i replaced the wire and wrapped that and the header. so i hoped that would fix it but i was wrong. i decided to hotwire the fan right from the battery and ran a switch to the cabin. that seemed to fix the problem until a couple days ago. it drives fine the first time i start it but if i turn it off and back on it'll kinda stall and idle funny until it shifts into a couple times then it drives perfect again until i turn it off and start the whole thing over again. it seems like if it sits for more than an hour or so its fine. and it doesn't do it every single time i turn it off and back on. plus i leave the fan on from the time i start the car until i turn it off. so i was wondering if anybody knew what it could be? i thought it could be the opti since they suck so much. im having a cam done and will probably replace the distributor by then. but i'd like to have it completely taken care of by then. and if it isn't the distributor then i have no idea what it is. any idea or input would be great. thanks guys
Old 05-16-2012, 09:27 PM
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I'd immediately suspect your plug wires even though you said you checked them. Open the hood and run the engine in the dark and look for any arcing (NOT the coronal flash you'll probably see).
Old 05-16-2012, 09:32 PM
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tried that and no luck. have msd 8.5 wires with two types of heat wrap on both. looked at each one up close and not even a sign of heat on any of the wraps. when i did the headers i didnt tune out the egr or air valves. i saw that a vacuum leak could cause this in another thread. i didn't plug the steel hose on the back of the block that went into back of the passenger side manifold. any chance this could be the cause? i've also seen a lot that blames the opti or coil. how likely would that be? i'm having a cam installed in a couple weeks and will have the opti changed then. but i'd like to have a clue what it was first. thanks
Old 05-16-2012, 10:05 PM
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Yep , if the EGR tube to the manifold is left unplugged and the EGR valve is not prpperly seated you'll have a vacuume leak.
Old 05-17-2012, 01:48 PM
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Originally Posted by WS Sick
Yep , if the EGR tube to the manifold is left unplugged and the EGR valve is not prpperly seated you'll have a vacuume leak.
wait...whats the yep to? the opti causin it or the egr tube?
Old 05-17-2012, 08:28 PM
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I had the same issue and found that one of the spark plug porcelins were cracked causing the mis-fire!

Joe



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