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

95 LT1 Rough Idle

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Old Jun 8, 2016 | 10:11 PM
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Default 95 LT1 Rough Idle

Hello all. Looking for direction on where to start to diagnose what the hell went wrong. After 20 mile blast canyon carving the other day sitting at a light coming home, a distinct change in the idle and overall feel of the engine abruptly started. I can feel a vibration in my seat and steering wheel. Same under acceleration and also a loss of power. No codes and same top tier fuel I've always used. Is it time to source obd1 data log software and compatible cable. I don't want to just start tossing parts hoping to stumble into a fix. Any and all input is appreciated. Thank you.

Last edited by steve1657; Jun 8, 2016 at 10:12 PM.
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Old Jun 8, 2016 | 10:15 PM
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Check your plug wires and plugs pull off one at a time till you find one that makes no differance. Look at that injector too.

Last edited by antfarmer2; Jun 8, 2016 at 10:17 PM.
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Old Jun 8, 2016 | 10:22 PM
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Originally Posted by antfarmer2
Check your plug wires and plugs pull off one at a time till you find one that makes no differance. Look at that injector too.


Probably a carbon tracked plug or an open wire, or something equally simple.
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Old Jun 8, 2016 | 10:29 PM
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Originally Posted by Amotoxracer


Probably a carbon tracked plug or an open wire, or something equally simple.
Kewl. Thank you Amotoxracer and AF2 for quick replies. I have project for Thursday night... probably friday also with my luck. one too many beers tonight to go ****ing around under the hood, probably have the engine out by time I was done
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Old Jun 8, 2016 | 10:50 PM
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Originally Posted by steve1657
Kewl. Thank you Amotoxracer and AF2 for quick replies. I have project for Thursday night... probably friday also with my luck. one too many beers tonight to go ****ing around under the hood, probably have the engine out by time I was done
That's ok go out and fire it up in the dark might see some arcking and sparking and know you found it just keep your beer in your hand won't do much damage then.
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Old Jun 8, 2016 | 11:00 PM
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Originally Posted by antfarmer2
That's ok go out and fire it up in the dark might see some arcking and sparking and know you found it just keep your beer in your hand won't do much damage then.
No spilled beer and no sparks... Although I refrained from shoving my head in the front to ensure there was nothing from the optispark
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Old Jun 8, 2016 | 11:04 PM
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Originally Posted by steve1657
No spilled beer and no sparks... Although I refrained from shoving my head in the front to ensure there was nothing from the optispark
Ok enjoy your nite it was worth a shot.

Last edited by antfarmer2; Jun 8, 2016 at 11:05 PM.
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Old Jun 9, 2016 | 08:13 PM
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Originally Posted by antfarmer2
Ok enjoy your nite it was worth a shot.
check codes, p0118 will give same symptom do you have hard start and you said you had a rough idol,, do the fans come on when they dont need to be on. this would be a symptom of a bad etc, replaced my coolant sensor still did it, turned out to be a loose connection on plug to sensor, replaced plug now good,
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Old Jun 9, 2016 | 08:21 PM
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Originally Posted by bob arrowsmith
check codes, p0118 will give same symptom do you have hard start and you said you had a rough idol,, do the fans come on when they dont need to be on. this would be a symptom of a bad etc, replaced my coolant sensor still did it, turned out to be a loose connection on plug to sensor, replaced plug now good,
Hello arrowsmith. Thanks for input it is all appreciated.
No codes and fires right up as it always has. Idle is rough, although the tach doesn't jump at all. Might just be the typical calibration. I was just out looking while grilling and my number 1 wire had rotated and was resting on the manifold shield. I can feel a decent cut in the wire and polish to the shield in same spot. Looks like I get to replace wires at 40k... but I have not tested or restarted yet to look for an arch.
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Old Jun 10, 2016 | 01:03 AM
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Originally Posted by steve1657
Hello arrowsmith. Thanks for input it is all appreciated.
No codes and fires right up as it always has. Idle is rough, although the tach doesn't jump at all. Might just be the typical calibration. I was just out looking while grilling and my number 1 wire had rotated and was resting on the manifold shield. I can feel a decent cut in the wire and polish to the shield in same spot. Looks like I get to replace wires at 40k... but I have not tested or restarted yet to look for an arch.
I think you found it, I would only replace the one offending wire and not the whole set.

Last edited by PatternDayTrader; Jun 10, 2016 at 01:07 AM.
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Old Jun 10, 2016 | 12:31 PM
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Originally Posted by Amotoxracer
I think you found it, I would only replace the one offending wire and not the whole set.
Thanks for the advice. Ordered a new set today! I'll start with replacing No. 1 and see if everything clears up... but knowing how good a friend I am with Murphy I will probably be back around with more questions.

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Old Jun 17, 2016 | 10:49 PM
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Installed new wires today, cleaned up the idle and she is running great with good power. makes me wonder how long that may have been causing an issue with spark as i feel like i can drive it like i stole it again! Thank you omotoxracer and ant for the tips and suggestions.
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Old Jun 17, 2016 | 11:26 PM
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Originally Posted by steve1657
Installed new wires today, cleaned up the idle and she is running great with good power. makes me wonder how long that may have been causing an issue with spark as i feel like i can drive it like i stole it again! Thank you omotoxracer and ant for the tips and suggestions.
good job
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