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

85 misfiring

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Old Jun 15, 2015 | 02:50 AM
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Default 85 misfiring

Stock l98 misfiring randomly. 170k miles. Hear it every couple of seconds when sitting at a stop light in drive and bad under moderate acceleration and occasionally when at low throttle. Almost non existent at cruising. Anyone got ideas?
Thanks
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Old Jun 15, 2015 | 07:41 AM
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Get the car in a dark area (garage or in the evening) and spray down the ignition wires with a spray bottle. Then watch for sparks.
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Old Jun 15, 2015 | 11:54 AM
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Originally Posted by ex-x-fire
Get the car in a dark area (garage or in the evening) and spray down the ignition wires with a spray bottle. Then watch for sparks.
that is a great suggestion.

OP make sure you come back and post results and solution so others can see it.
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Old Jun 15, 2015 | 12:21 PM
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Sounds good. I'll try it tonight. Any areas in specific or just the length of all 8 wires?
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Old Jun 15, 2015 | 02:19 PM
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Originally Posted by .50ae
Sounds good. I'll try it tonight. Any areas in specific or just the length of all 8 wires?
bad wire and or fouled plug(s)
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Old Jun 27, 2015 | 09:45 PM
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Sorry about the late reply guys. I finally got around to buying plugs (nearest auto parts store is 30 miles away) and replacing them all. One plug in particular, far back passenger side, had insane amounts of carbon built up on it to the point that I don't know how it was firing at all. Haven't driven it yet but I'm taking taking a wild guess and saying that's the problem. Thanks for the help guys.
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Old Jun 28, 2015 | 01:09 AM
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Originally Posted by .50ae
I'm taking taking a wild guess and saying that's the problem. Thanks for the help guys.
I'm taking a wild guess and saying that's NOT the problem. I think you have a problem with the plug wire or connections, which is why the plug is not firing and getting carboned up.
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Old Jun 28, 2015 | 07:16 PM
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Originally Posted by Cliff Harris
I'm taking a wild guess and saying that's NOT the problem. I think you have a problem with the plug wire or connections, which is why the plug is not firing and getting carboned up.
I dunno man it drove great on the 20 minute drive to work.
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Old Jun 28, 2015 | 07:29 PM
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Wait two or three weeks and then check #8 plug again. Check to be sure it is carbon build up or is it oil. If it is oil then you need to replace the intake gasket.
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Old Jun 28, 2015 | 09:26 PM
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Originally Posted by .50ae
I dunno man it drove great on the 20 minute drive to work.
did your plug look like this?


This was mine caused by a bad injector. Can also be caused by a bad wire or wire not seated correctly on distributor.
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Old Jun 29, 2015 | 02:03 AM
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Originally Posted by Cruisinfanatic
did your plug look like this?


This was mine caused by a bad injector. Can also be caused by a bad wire or wire not seated correctly on distributor.
No my plug was worse believe it or not. I put about 150 miles on it while it was missing because of work though. I think it was probably only minor carbon fouling and it just got worse and worse as I drove it. I'll keep you guys updated and let you know in a couple weeks of any problems come up. My injectors were rebuilt 2 years ago so I doubt it's a bad injector but you never know.
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