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

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Old Apr 19, 2012 | 11:41 AM
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Default Need help.

Newbie here, although I've read the site for years, never had a reason to post until now. I have a 95 vert that is idling high and experiencing a pretty significant drop in fuel efficiency (around 22mpg on freeway when it should be getting around 28-29). Took it to my dealer and they swear its idling within specs. I've owned these cars for years and know it shouldn's be turning 2400 @ 70mph.

I had a SES light come on and computer is showing a bad o2 sensor. It is being replaced today but the SA told me that a bad o2 sensor wouldn't be causing a high idle and also wouldn't cause enough of a drop in fuel efficiency to even notice.

Any suggestions/ideas would be most appreciated.
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Old Apr 19, 2012 | 11:59 AM
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I'm not sure what rpm your motor was turning @ 70mph before, but if it is higher now, your converter may not be locking up during cruise conditions which will greatly affect fuel economy.
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Old Apr 19, 2012 | 12:41 PM
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Thanks 383, it is bone stock and turned around 1900 @ 70mph before. I'll report back my findings after the new o2 sensor.

I guess my main question is could that possibly be the cause for the high idling? Maybe the computer forcing it into close loop?

It's a low mileage car @ 41k.

Any help/suggestions appreciated.
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Old Apr 19, 2012 | 01:23 PM
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So what exactly is it idling at? Sitting there in Park (it's an A4, right?)
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Old Apr 19, 2012 | 01:48 PM
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It's idling around 600-700. Shop just called and they discovered another code for a bad EGR valve. Could this be the culprit?
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Old Apr 19, 2012 | 01:48 PM
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it is an A4
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Old Apr 19, 2012 | 11:03 PM
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bham as in Birmingham AL? Got a great shop I did business with if you need pro help.
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Old Apr 20, 2012 | 01:04 AM
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600-700 RPM is normal idle. Why do you think that's high?

Are you sure the trans is going into OD?
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Old Apr 20, 2012 | 07:21 AM
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Originally Posted by bhamvette14
It's idling around 600-700. Shop just called and they discovered another code for a bad EGR valve. Could this be the culprit?
That's not a high idle. My guess is either the tranny is slipping, or it's not going into OD. Can you hear/feel it shift into OD?
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