Performance?

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Aug 28, 2016 | 12:37 PM

bolling

Thread Starter

Instructor

Joined: Apr 2014

Posts: 202

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From: Crescent City, IL IL

Performance?

My 88 starts and drives perfectly but the performance seems better when it is first started and driven. Any ideas? Once warmed up it seems more sluggish.
Thanks

Last edited by bolling; Aug 28, 2016 at 12:38 PM.

Aug 28, 2016 | 12:57 PM

93 lt1 vette

Racer

Joined: Oct 2011

Posts: 270

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From: Benching 455RAW Texas

Yep that's what happens in the summer to an internal combustion engine. Now if there is a miss bog rough idle that would a different story at operating temp.

Aug 28, 2016 | 01:05 PM

bolling

Thread Starter

Instructor

Joined: Apr 2014

Posts: 202

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From: Crescent City, IL IL

Quote:

Originally Posted by 93 lt1 vette

Yep that's what happens in the summer to an internal combustion engine. Now if there is a miss bog rough idle that would a different story at operating temp.

I have had several corvettes and this is first that it is noticeable. It seems after it leans out after cold start it could use more fuel as in the cold start mode.

Aug 28, 2016 | 01:14 PM

antfarmer2

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Old slow o2.

Aug 28, 2016 | 01:34 PM

bolling

Thread Starter

Instructor

Joined: Apr 2014

Posts: 202

Likes: 1

From: Crescent City, IL IL

Quote:

Originally Posted by antfarmer2

Old slow o2.

Is that fairly common on older C4s even though it has only 34000 miles. Thanks for the help.

Aug 28, 2016 | 01:43 PM

antfarmer2

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Quote:

Originally Posted by bolling

Is that fairly common on older C4s even though it has only 34000 miles. Thanks for the help.

It is almost 30 years old might look at your puter temp sensor too. And vacumm lines.

Aug 28, 2016 | 02:01 PM

ddahlgren

Melting Slicks

Joined: Dec 2008

Posts: 2,772

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From: Mystic CT

It is lean in closed loop. Looking for 14.7/1 for real gas E10 needs to be 14.3. I would put in a heated O2 and if possible raise fuel pressure 3 or 4 lbs as a start to fatten it up a bit.

Aug 29, 2016 | 09:55 AM

QCVette

Le Mans Master

Joined: Jun 2009

Posts: 6,528

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From: South Dakota

I agree with the others that it is likely to be the O2 sensor.

When you first start it the car is running in open loop meaning it runs only off the computer program and is not adjusting to the sensors until it is warmed up some. Once it reaches temperature it will go to a closed loop and base the adjustments of the fuel and spark based off the sensors.

So the tune could be good as shown when you first start it, and then when it goes into closed loop it may be getting bad data from the sensors and not running as good as it should.

I would try the O2 sensors first.

Good luck.