Tune Up?
Thread Starter
Racer
Joined: Feb 2012
Posts: 442
Likes: 23
From: Seattle Washington
Tune Up?
I have scheduled to take my 85 in for a tune up next week. The Vette is all original and has 87K on the clock. It does have a Hypertech Street runner Chip in it. The engine runs fairly good with the exception of a slight stumble while stopped at a stop light and, I'm only getting about 12 MPG around town. My question is: what all should I expect the mechanic to do (He specializes in Corvette's) and can I expect better gas milage?
Thanks,JW
Thanks,JW
Le Mans Master
Joined: Jun 2009
Posts: 6,528
Likes: 752
From: South Dakota
"Tune up" can mean different things to different people.
Usually it will be some combination or all of the following. Corvettes or other cars all need the same things (fuel, air, spark, compression) so really not much different than other cars.
New correctly gapped spark plugs.
New plug wires.
New distributor cap and rotor.
Check/adjust timing.
At 87K and 28 years it is time for all of them.
Some may also include a new air filter and fuel filter, but I never considered these as tune up parts. (but it may be time for them too)
Less common are items like setting the TPS, and idle adjustments. Most will not do these unless there is a problem. Most of the fuel and spark timing parameters are controlled by the computer and a tune up will not burn a new chip for you. Your Hypertech chip does that for you.
As for better mileage, it depends on whether any of those items were bad or not. Frequently it can help some. Your in town mileage is very dependant on how you drive, so guessing a number of mpg your car should get is hard to do. My '85 4+3 gets a little better than yours in town and about 24 or 25 on the highway.
Good luck.
Usually it will be some combination or all of the following. Corvettes or other cars all need the same things (fuel, air, spark, compression) so really not much different than other cars.
New correctly gapped spark plugs.
New plug wires.
New distributor cap and rotor.
Check/adjust timing.
At 87K and 28 years it is time for all of them.
Some may also include a new air filter and fuel filter, but I never considered these as tune up parts. (but it may be time for them too)
Less common are items like setting the TPS, and idle adjustments. Most will not do these unless there is a problem. Most of the fuel and spark timing parameters are controlled by the computer and a tune up will not burn a new chip for you. Your Hypertech chip does that for you.
As for better mileage, it depends on whether any of those items were bad or not. Frequently it can help some. Your in town mileage is very dependant on how you drive, so guessing a number of mpg your car should get is hard to do. My '85 4+3 gets a little better than yours in town and about 24 or 25 on the highway.
Good luck.
Team Owner
Joined: Sep 2001
Posts: 62,160
Likes: 1,733
From: Athens AL
C7 of the Year - Unmodified Finalist 2021
C4 of Year Finalist (performance mods) 2019
In addition to what has been recommended, if you havent changed the brake fluid out then you need to do so. You may also need to run seafoam or another cleaner through the intake manifold.
The mileage issue is likely related to a dying O2 sensor, unless there is a SES code that would suggest something else?
The mileage issue is likely related to a dying O2 sensor, unless there is a SES code that would suggest something else?
Race Director
Joined: Sep 2003
Posts: 16,838
Likes: 341
From: Database Error Indiana
In addition to what has been recommended, if you havent changed the brake fluid out then you need to do so. You may also need to run seafoam or another cleaner through the intake manifold.
The mileage issue is likely related to a dying O2 sensor, unless there is a SES code that would suggest something else?
The mileage issue is likely related to a dying O2 sensor, unless there is a SES code that would suggest something else?
O2 sensor will kill fuel consumption. I hate when someone posts that they are taking a C4 to have it serviced. With a little work, the owner can be the best mechanic they know.
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Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
Wear and tear is compensated for with Electronic Fuel Injection so I'd start with a Scan to check Fuel Delivery and Sensor Input. That'll take some of the guess work out of it. Frankly, plugs last forever; as do O2's (by Law out here, they pretty much have to and it doesn't matter where you live, your Vette came with the same stuff), wires don't. Injectors, if they've never been cleaned, might benefit from something, though I've tried shooting 3M Injector Cleaner through the rail with zero change in performance or Scan Data. I think the easier route would be to clean the throttle body and replace the fuel and air filters - assuming your Scan doesn't show that it's having to correct for an extreme rich or lean condition and that the Coolant Temp Sensor matches Ambient after it's sat overnight.