Low power, poor MPG - Corvette Forum
 
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post #1 of 3 (permalink) Old 03-17-2009, 01:47 AM Thread Starter
 
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Cool Low power, poor MPG

I have a 94 coupe, LT-1, auto. I do not have any codes at this times, no check engine lights. I have a Wide-Open Magnaflow exhaust and K&N filter. Other than that the car is stock running gear. I have 78K on the car now. It never refuses to start and runs okay, just not like what I expect from a corvette. I have owned the car for 3 years and up until this last fall it was my daily driver. If i rev the car in idle, it is slow to respond and then revs better in the mid-range. On the street it seems to be the same meaning that if I want to accelerate it doesn't rev like I think it should. I have read that having a louder than stock exhaust (mufflers or headers) can cause the knock sensor to retard timing by as much as 21 degrees. Has anyone else experienced this? The article that I read suggested replacing the LT-1 knock sensor with a LT-4 sensor. Any reply would be appreciated.
94blackrosey is offline  
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post #2 of 3 (permalink) Old 03-18-2009, 12:47 PM
 
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I think that I would be looking at the catalytic converter. Do you notice any smell like rotten eggs when its hot?? There is an easy way to check for an obstructed exhaust system using just a vacuum gauge.
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post #3 of 3 (permalink) Old 03-22-2009, 12:52 PM
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Quote:
Originally Posted by 94blackrosey View Post
I have a 94 coupe, LT-1, auto. I do not have any codes at this times, no check engine lights. I have a Wide-Open Magnaflow exhaust and K&N filter. Other than that the car is stock running gear. I have 78K on the car now. It never refuses to start and runs okay, just not like what I expect from a corvette. I have owned the car for 3 years and up until this last fall it was my daily driver. If i rev the car in idle, it is slow to respond and then revs better in the mid-range. On the street it seems to be the same meaning that if I want to accelerate it doesn't rev like I think it should. I have read that having a louder than stock exhaust (mufflers or headers) can cause the knock sensor to retard timing by as much as 21 degrees. Has anyone else experienced this? The article that I read suggested replacing the LT-1 knock sensor with a LT-4 sensor. Any reply would be appreciated.
I've heard of replacing the "knock module" in the ECM with the LT4 module..but that's only on later models of LT1s( earlier modules are not replaceable),not sure on a '94. Before I'd do that though I'd check check the converters for being stopped up (as was stated above) and i'd check or have checked the fuel pressure and the fuel pressure regulator, sometimes the diaphragm will rupture and suck fuel into the vacuum hose causing poor mpg and running problems. Lastly if the exhaust was installed since you've owned the car....Is that when the problems started ?
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