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Rough and won't idle

Old 11-11-2012, 12:55 PM
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Yellow Z
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Default Rough and won't idle

I am looking for suggestions. C5 corvette with a TVS2300 magnuson supercharger. Methanol injection in the air bridge after the MAF sensor. The car will not idle and runs extremely rough. It throws a current p0300 misfire code and no other codes. I have checked the coils and they are firing fine. I replaced the plugs and plug wires with no improvement. I don't see any issues with the ground wires. There do not seem to be any vacuum leaks. Can a broken valve spring cause this?

The misfire code has been present off and on for a while. By that i mean sometimes as a history code and sometimes current. Recently it threw an MAF code P0101 but that has gone away. I cleaned the MAF sensor and that may be the reason why the p0101 code went away.

The car can be driven but will not idle and runs really really rough under any sort of throttle. Thanks in advance for any suggestions.
Old 11-11-2012, 01:02 PM
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pewter99
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you may be onto it....sounds like a recent post same type of symptoms....time to pull the covers and see
Old 11-11-2012, 01:41 PM
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cptinjak
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So this problem is intermittent or continuous?

How did you check for vacuum leaks?

If this problem is constant, and there are truly no vacuum leaks, I would do a compression test ASAP. Also pull the valve covers to visually inspect the springs. There is not much else that can be troubleshot until you confirm those things.

Jack
Old 11-11-2012, 04:47 PM
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Originally Posted by cptinjak
So this problem is intermittent or continuous?

How did you check for vacuum leaks?

If this problem is constant, and there are truly no vacuum leaks, I would do a compression test ASAP. Also pull the valve covers to visually inspect the springs. There is not much else that can be troubleshot until you confirm those things.

Jack
It is continuous. Visual check for vacuum leaks. My next step is to pull the valve covers and see what I find. I am open to suggestions on how best to check for vacuum leaks.
Old 11-11-2012, 05:10 PM
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Originally Posted by Yellow Z
It is continuous. Visual check for vacuum leaks. My next step is to pull the valve covers and see what I find. I am open to suggestions on how best to check for vacuum leaks.
Visual inspections are pretty much worthless for vacuum leaks. You need to do a leak down test and a compression test.

Did something happen to the car? Was it over-revved at any point? Or did this problem just occur out of nowhere?

Jack
Old 11-11-2012, 06:42 PM
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Originally Posted by cptinjak
Visual inspections are pretty much worthless for vacuum leaks. You need to do a leak down test and a compression test.

Did something happen to the car? Was it over-revved at any point? Or did this problem just occur out of nowhere?

Jack
Out of nowhere.
Old 11-11-2012, 07:54 PM
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Just went through the exact same as you are describing, changed wires and plugs, checked grounds and for vaccum leaks. Broken intake spring on #2. I wouldn't start it anymore until you check the springs. I'm doing the trunion upgrade while I'm in there. Just waiting for the springs to arrive. Good luck and I hope all is intact in your valvetrain. By the way I was just going to a group lunch, driving very old lady-like, when **** hit the fan. Had it towed home from lunch on suspicion of it being a valve spring.

Last edited by punz; 11-11-2012 at 08:02 PM.

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