C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

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Old Jul 30, 2009 | 03:48 PM
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My car is a 93 lt1. About a year and a half I replaced the opti with a MSD unit, blaster coil, 8.5mm wires and Denso iridium plugs (the original opti would cut out and back fire: however, it would run ok and ocasionally it would get and go). The first few months I was happy with the new set up and then something happened, mileage and performance dropped off. I started locking for possible problems. I have been dealing with ignition troubles for weeks. The car has a miss at idle that I can here and if the air is on you can feel it. I have checked grounds, ICM, coil, wires and plugs. Still have a miss. The tech at MSD said it would through a code or not run if it was the distributor. I told him my original dis did not set a code and it would run, this seemed to make him mad (no help). So, the problems that I have are: wire arcing, miss at multiple cylinders(random), poor economy and lack of power. I have tried switching out ignition componets except the dis for obvious reasons. Does this sound like it would be a problem with the distributor or maybe the computer?
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Old Jul 30, 2009 | 03:56 PM
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You mention codes, but have you actually checked for codes yet?
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Old Jul 30, 2009 | 06:20 PM
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Could be an injector issue.
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Old Jul 31, 2009 | 02:57 PM
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I got a 12 and a 32. I cleared the code before and it will stay gone for months most time. The 32 code is a EGR and the valve moves freely with no leak at the gasket. I pulled the intake over winter replaced the gasket which fixed my oil leak at the back of the block. I was thinking the 32 was from the lower back pressure of the Borla cat back. The fuel pressure I was getting at Idle was 34psi and with the vacum off it is 42-43psi. Drove the car with FPR vac disconnected and had the same miss: however, the car would get better cruising mileage(about 24mpg at a seady 60mph).
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Old Aug 1, 2009 | 05:49 PM
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You mentioned a Borla Exhaust. Do you have any other mods? Also do you have a factory service manual? There is a procedure for checking the ignition system as well as the PCM and fuel system. Stay after the misfire and preformance issues. Don't get discouraged. You will sort them out.
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Old Aug 1, 2009 | 08:23 PM
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Couple of simple, primitive, and free things to do:
1. Start it up in a dark place and look for arcing plug wires.
2. Use a cheap heat gun and read the temp at the exhaust manifold for each cylinder.
3. What were we talking about again?
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