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Why is my C5 slow?

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Old 12-09-2006, 02:14 AM   #1
jah
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Default Why is my C5 slow?

At the track today, I did the 1/4 mile in 15.1 sec. with the car loaded with full tank of gas (I weigh 230lbs). It's all stock '98 coupe with 49,000 miles. What are some areas I can look into? Change the air filter? Check/change the spark plugs? What else?

Thanks all.
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Old 12-09-2006, 02:23 AM   #2
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what was your 60'
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Old 12-09-2006, 02:29 AM   #3
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I would guess a fuel problem
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Old 12-09-2006, 02:29 AM   #4
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Somethings terribly wrong.. what were your #'s...please post all of them
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Old 12-09-2006, 02:32 AM   #5
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15.1,15.2,15.4,15.1

not sure about 60 times, but that part seems OK, my top end is where I lost - top speed always 91mph.

How can I check the right fuel delivery?

What other things can I check?
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Old 12-09-2006, 02:45 AM   #6
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Holy crap! did the car always feel this slow? When did it feel like it lost power.
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Old 12-09-2006, 02:49 AM   #7
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Need 60 foot times.
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Old 12-09-2006, 02:53 AM   #8
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I just got it. What should the 1/4 times be like? low to mid 13's? Top speed - should be in the 100's right? What can I check to help me locate the problem(s)?
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Old 12-09-2006, 02:56 AM   #9
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A bone stock MN6 w/ the 345 hp LS1 should run low 13's @ 106ish mph. For reference I piloted my mom's bone stock '99 MN6 to a 13.1 @ 107.
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Old 12-09-2006, 03:09 AM   #10
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What is your 60 ft? Stick or auto trans? Where do you live? My bone stock auto 2004 went 12.92 @ 107
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Old 12-09-2006, 03:34 AM   #11
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Thanks guys, I can see that somethings wrong. I live in El Paso, TX and was told that this stock Auto Vette belonged to some doctor before he traded it in w/49,000 mi.

What steps do I take to check out problem areas. I think it might be the fuel or air delivery - change filters? Sorry, I didn't get 60' times, but I seemed to do well there. The other cars would pass me after we got half way down the 1/4 mile course.

Thanks
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Old 12-09-2006, 03:48 AM   #12
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We still need to know what your 60" times were. Also, did you run the car in 3rd gear since it is an automatic? If you ran it in 4th, that is part of the problem. You also likely have the 2.73 rear end and not the optional 3.15 available for automatics.

If your 60' times are too high, this will also explain some of the low mph.

Do you have heavy aftermarket wheels on the car? Is there added weight such as subwoofer box? Full tank of gas also doesn't help.

The DA or outside temperature also is a factor. Elevation is also a factor but not likely in Texas.
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Old 12-09-2006, 04:05 AM   #13
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wheel are stock. Temp out side was around 50F.

I used overdrive. Should I use 3rd all the way down?

I had the traction control on. Should I turn it off?

Also, how can I check the transmittion oil? I think I saw leaks on the driveway before I left to the drag races? This alone might be the cause - no?

Last edited by jah; 12-09-2006 at 04:10 AM.
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Old 12-09-2006, 04:11 AM   #14
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Quote:
Originally Posted by jah
wheel are stock. Temp out side was around 50F.

I used overdrive. Should I use 3rd all the way down?

I had the traction control on. Should I turn it off?

put the competitive driving mode on.....hold the T/C button down for 8 sec....while ur stopped.....and i leave it in drive....??.......it seems the be the fastest when i do that....ive never ran down a real track b4....go to a private closed road and practice....u will be able to feel the car urself...u dont need a clock telling u good luck
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Old 12-09-2006, 04:18 AM   #15
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Yes, use drive all the way down the 1/4. Turn the traction control off.

The tranny fluid level is not simple to check. It is easier on a lift since the tranny is in the rear of the car.
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Old 12-09-2006, 04:41 AM   #16
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I will turn the traction control off next time (I can't believe I didn't think of that there!). Could this make that big of a difference?

What else can I check? Fuel/Air filters? Should I have a shop check it out? Will a diagnostic test tell me anything or do they have to do a dyno on it? About how much is that (incl. vette tax!)?
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Old 12-09-2006, 05:39 AM   #17
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Fuel filter! S/B replaced at 30K.
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Old 12-09-2006, 06:00 AM   #18
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There has to be something wrong. I've left the traction control on while bracket racing and I still cut 2.1xx 60s in 85 degree heat and went 13.6 letting off. I also have 2.73 gears and was still stock when I went 12.92 @ 107. There might be something going on there with your car.
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Old 12-09-2006, 06:05 AM   #19
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Make sure you're pushing the pedal all the way down
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Old 12-09-2006, 07:43 AM   #20
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It doesn't matter what his 60' times are, what gear he was in, what driving mode he was in, etc. If he's only trapping 91 mph he's WAY down on power. Like something on the order of 100 rwhp down. The car needs attention from a good Corvette mechanic. If it otherwise runs well (not rough or smoking) it has to be something relatively simple. That or somebody swapped in a L-48 while he wasn't looking!

I bet this guy is going to get the cheapest 100 rwhp boost on record.

Last edited by Gannet; 12-09-2006 at 07:51 AM.
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