Wierd Idle Surging and Misfiring
05-26-2013, 07:39 PM
#21
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usually when it seems like it does it more when warm its ICM related. Most auto stores should be able to check it for you or its getting crazy spark when warmed up chances are its that or the good ol optispark.
05-26-2013, 09:10 PM
#22
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I bought a used ICM to swap in and try. Should have it next week. If that doesnt do it, then it'll be the Optispark. The way it acts to me is the spark is weak. Just doesnt seem like its firing strong enough. Theres a slight pop to the exhaust at idle and misfires the more load gets applied. Engine breaks up completely under WOT and above 5000rpm. Sometimes the symptoms clear after running over 15-20 minutes and cycling the engine on and off a few times. Definitly a dodgy ignition system problem.
05-27-2013, 07:07 AM
#23
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Hate to say it but yeah you probably are looking at an opti issue. try the ICM first tho. they are way way cheaper. I bought a tester from autozone for about 8bucks and its adjustable to check the actual spark. should be able to jump an inch to an an inch and a half and be nice and bright. (Just a test I know how much of a pain tearing down to the opti is)
06-12-2013, 07:43 PM
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Nope. Car acts like the spark is weak and misfires the more load you apply. I'm saving up for an optispark at the moment. Damn ac delco optis are rediculous priced.
06-12-2013, 07:47 PM
#26
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what o2 sensors are in the vehicle. My car went to a shop to get subframe connectors welded on and while there it started a pop at idle.... While driving it home it started misfiring real bad, nothing like having a heda cam lt1 hardly making it up a hill misfiring and sounding like straight garbage on the highway haha. Either way got home and swapped out an o2 sensor and disconnected the battery and it was fine. You should try disconnecting the battery ground for about 30 minutes as well just before you spend anything more. easy and free to do haha
06-12-2013, 08:09 PM
#27
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Done the battery disconnect before. Not the problem. O2's are Delphi units replaced 2 months ago. No codes on the vehicle at all. It's a weak spark issue. New plugs and wires are on the car. Only thing left is the Opti. I replaced the original with a Jegs unit and it ran great for 500 miles or so and now it just misses more and more with time.
06-15-2013, 11:47 AM
#28
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Get that optispark out of there!!!! I run an LT1 383 with a procharger and the optispark was misfiring, bent the spark plug tong over onto the electrode. I replaced the plug and it would run fine until I gave it any kind of boost and foul the plug again. Eventualy taking out a piston gland. Now its at the machine shop.
06-19-2013, 09:19 PM
#31
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You had to be running that thing hard with alot of detonation to get that to happen. I dont even drive mine right now because i know all it does is misfire.
06-20-2013, 12:02 AM
#32
After reading all this my main suspicions were ICM and and your wire harness. You've pretty much replaced everything else and checked grounds. I see you also bought a used ICM to rule that out.
So it started happening after you modified the exhaust? Maybe the wires for your O2 sensors are either burned or they're close enough that they get heat soaked after a few minutes and all the built up resistance from the extra heat is interfering with the signal. That could screw up all kinds of things.
So it started happening after you modified the exhaust? Maybe the wires for your O2 sensors are either burned or they're close enough that they get heat soaked after a few minutes and all the built up resistance from the extra heat is interfering with the signal. That could screw up all kinds of things.
06-20-2013, 05:34 AM
#33
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3 years ago I took the Opti, water pump, and heads off the car. Let the car sit for 2 years then put it all back together. New head gaskets, Jegs Opti, and new water pump. Also did the headers the same time. Everything ran good for a few hundred miles then it started misfiring little more the longer I went. I redid the O2 wires and sensors twice to rule it out. It's a weak spark issue, just don't have the funds to put a good Opti on at the moment so the car sits.
09-15-2013, 09:49 PM
#36
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Been a few months but i decided to F with the LT1 to get it running better again. Found some chewed Fuel Injector wires which one was damn near chewed through. Fixed that wire and the car runs smooth again. Currently still using the Jegs Optispark. Maybe it will hold up. At this point im just glad the car is driveable again. Lesson learned from all this, Check all the old crappy wiring before replacing parts. Lol.
